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Matt's 1970 Opel GT - Project Log

75K views 350 replies 26 participants last post by  jclars 
#1 ·
I've decided to convert a 1970 Opel GT to electric.

As usual with my builds, this is a budget build not just for low cost, but trying to use as much unwanted/recycled/garbage/repurposed items as possible. It's not a performance build.

I'll try to update this front post to act as a table of contents for the progress on the thread.

To be updated, but, rough project specs:

- 1970 Opel GT ($200, but, $700, and up as I go).
- AC Forklift motor (free, from a scrapyard).
- Prius Controller (probably, haven't bought yet), with Damian's prototype brain for it. This might also be the charger.
- Recycled 18650 batteries from tool packs (already have).
- 70mph (110 km/hr) or so top speed (highway speed)
- At least 60 mile (100km) range, 120 mile (200km) would be better, I think I have enough cells.
 
#100 ·
Not having immediate success with buying a coupler, nor casting, nor EDM, I've spent some time laying out my options. Organizing my thoughts, not much progress to show.

1 - Hire a machine shop to fabricate a coupler.
2 - Fabricate a coupler myself, using a machine shop.
3 - Buy a Massey-Ferguson tractor PTO clutch to match the motor side, weld it to something for the transmission shaft.
4 - Continue with EDM experiments.
5 - Grind off/fill in the splines, make a taper-lock coupler.
6 - Weld the motor shaft directly to the transmission shaft.
7 - Wait for the forklift yard to maybe have a matching coupler.
8 - Carve a coupler by hand with a saw and file.
9 - Cast a coupler from aluminum or zamak.

And in detail why/why not:

1 - Hire a machine shop to fabricate a coupler.

- It'll get done right.
- It'll be the most expensive.
- It'll probably take some time.


2 - Fabricate a coupler myself, using a machine shop.

- I have access to a machine shop with $50,000 of tools. A giant lathe, a manual milling machine, a Tormach CNC milling machine, etc. I'm trained on all the machinery, I can let myself in 24/7 and use whatever equipment I want, make as much noise as I want. No one else will be there at night I'll have the place to myself.
- It's cheating, on a simple project, to go use $50,000 of industrial machinery. Even more so to throw a piece in a machine and click a button and let the computer do it (which I could do, like, tomorrow). In as much as my project might be educational, this is the antithesis of what anyone else could get done at home. It's like commuting in a helicopter.
- I used to spend a lot of time there, don't have time to be there regularly anymore, and don't really want to remember how much I miss it.


3 - Buy a Massey-Ferguson tractor PTO clutch to match the motor side, weld it to something for the transmission shaft.

- Ruining something brand new just for the splines.
- Kind of expensive.
- Still only a partial solution, still have to kludge the transmission half.
- Probably won't be very deep, (might need 2 couplers).


4 - Continue with EDM experiments.

- My EDM machine has been on pause for 10 years, it would be nice to finish it and use it.
- I'm most interested in this.
- I've already sunk a bunch of time into it.
- Casting hasn't gone well but is becoming passible.
- Solution might not be sufficiently accurate. EDM has small, but existant air gap between electrode and workpiece by function of the process itself. EDM can be about 0.0005" accurate (half-thou), but that would be around a circumference so 0.001" total. Automotive fit is usually around 0.001" for sliding parts, so I would have to be at the limit of the technology on a home-built machine. This isn't a rigidity constraint like on a milling machine, it's a configurable attribute related to voltage, current and frequency, but the construction of my plunge die has to be within those tolerances for that to matter. Alternatively I could undersize my electrode to compensate, but that means I can't just cast an image of the shaft, I'd have to machine it smaller, making the whole process moot.
- I risk going off on a tangent project that will sink too much time (for example, as it already has).


5 - Grind off/fill in the splines, make a taper-lock coupler.

- A taper-lock is just a barrel of aluminum with a narrow slot in it and some bolts to squeeze that gap (nearly) shut.
- It's apparently as strong as a weld.
- It's proven strong enough for DIY EVs in the past, it's the common machined solution.
- I don't like damaging the motor splines because I can't undo that later.
- I could fill in the splines with JB Weld and leave it large, it's just surface to squeeze on.
- 2" aluminum bar in short lengths is probably as much as a PTO clutch would cost, and I doubt my machining ability with steel.
- I could also/instead cut a keyway and use a keyed shaft. But I presume there's a reason that keyed shafts are never used like this even though that's simpler and easier.


6 - Weld the motor shaft directly to the transmission shaft.

- Shaft is permanently damaged if I screw it up.
- Can I create a jig to weld it sufficiently square and centered?
- Solution in general is pretty permanent, most other solutions I can just abandon and try something else with no consequence.
- It limits serviceability or making other changes.
- This has always been my backup plan, and tempting.


7 - Wait for the forklift yard to maybe have a matching coupler.

- Forklift yard mentioned they have 2 more machines like the one I took the motor from, that they're combining into one. They'd pull the gearbox for me so I could recover the matching splined shaft. Though they're not sure when, or if they have a buyer for that. Or time to do it.
- This has been my backup plan for a while, knowing it might be "a month" or more, but, it's been 6 weeks not no call yet so, probably won't happen.
- I have no idea how long I might wait for that to happen.
- Is still only half a solution.


8 - Carve a coupler by hand with a hack saw and file.

- Seems like the worst choice, but it's so, so simple, and unlike welding, not a permanent commitment. It just takes time. And honestly not that much time compared to fancier solutions.
- I've done it before, and it worked then.
- I hate this.


9 - Cast a coupler from aluminum or zamak.

- Instead of casting the female image in a plaster mold, then pouring copper into this mold to create a male image, then using the male to EDM out a matching female, instead just cast the female directly.
- Make a silicone mold of the splines, use that only as a shape to pack a high-temp sand mold, pour metal into the sand mold.
- Aluminum has a lower melting point than copper, so if I could cast copper I can easily cast aluminum.
- Zamak (Zinc/Aluminum) is stronger than bare aluminum, melts at a lower temperature, and is considered "zero machining" surface finish quality.


...


As much as I hate throwing away my casting and EDM efforts of the last 6 weeks, and I'm confident it'll eventually work, I'm worried that I'll get it working but it still won't be good enough regardless of my effort because of physical limits. I guess it's time to put my EDM project back on the shelf.

I think I'm going to try casting a Zamak coupler. A car guy's suggestion of using silicone mold to cast tin (no good) gave me the idea that, the only reason I can't cast a female directly is because I don't have a female mold. A plaster mold wouldn't survive being used as an image, but silicone would be fine to pack sand around and then remove.

If that fails, Plan B is an aluminum taper-lock.

If that fails, Plan C is to just weld it up solid. Or braze it so there's less warpage.
 
#101 ·
Onto less boring things, progress and pics!

Casting Progress:

- I cleaned up the other half of my borrowed garage, and built another pair of 8' long 2x4 shelves. So much room, for activities!

- The very last thing I did was move some cheap plastic wall-hanging shelves. Behind which I discovered... a 240v 50a outlet. Perfect timing, as I'm done pretty much all my welding with my crappy 120v 15a welder. *sigh*

- I finally got 2 molds to turn out decently. The secret was to be less ambitious about depth (1/4-3/8"), and, to mix yellow fiberglass insulation into the plaster so that it wouldn't crack across the whole mold when removing it (it worked).

- New casting (right) turned out great. On the outside. I forgot to pre-heat the mold so, steam boiled out of the mold when I poured, and volcano'd all the copper away. The surface is all that's left. Which is fine for EDM, I'm only using the surface. Surface finish is also great, only needs light touchup:



- Ruined my steel crucible by letting it get too hot. Top 1/3 of my copper poured out into the sand, bottom 2/3 is kind of stuck in a furance I can't use now. Oops.



- No problem, I'll go back to using my firebrick directly. Oops. I liquefied the firebrick into glass and then burned through it too:



- It probably makes sense if I explain that I upgraded my carbon arc furnace before this, it puts out a lot more heat now. Probably close to 500a at 24v.

None of this matters, since I probably won't be doing EDM. I might be using the furnace still though.


Brakes:

- Let's have a closer look at the master cylinder.



- What about the brake booster?



I might have wrecked it, trying to unscrew the vacuum attachment. It now sloppily spins (but didn't come out of the metal enclosure).

- Front brakes apart.



Stripped one of the j-tube fittings (no problem, I'll screw it back together using vice grips, and just always disconnect the other end of the rubber hose in the future instead). Found broke the cross-shaped brake pad clamp on one side. Pistons okay on one side, other side the rubber was cracked.

- A transformation!



How did I restore them so well? I didn't. I bought them out of the local parts co-op, recently donated from another member who wanted to use them but upgraded to a big brake package instead. Ended up being free because of parts I've contributed that I didn't need (like a good gas tank from a desert vehicle).

I had no interest or skill in refurbishing brake parts so I just paid other GT guy to do it for me. Great value and peace of mind on something I don't care about doing and just want done.

My old reservoir had a matchbook-sized hole in it, and when we tried to pull it off, it half shattered, half crumbled in his hands. Desert car - win on the metal, lose on the rubber and plastic. Was junk anyway, but, yeah.

- My brake fluid reservoir cap was also cracked, so I took it to the junkyard and practised on 30 or so vehicles until I found one that matched. '04 and '07 Mazda 3 had screw caps (not tabbed caps) that seems to fit perfectly. $2.




Windows and Doors:

- I spend a couple days reading old threads about converting the Opel GT crank mechanism to power windows. Consensus seems to be 1996-2000 Honda Civic sedan, front window regulators are a good match. They are known to be durable unlike other brands.



Despite so many threads, there's not a consistent write up, nor labelled diagram, and conjecture is mixed in with proven results so it's hard to know what to door use. I'll try to write an article about that if I can colimate the advice correctly.

In brief:

- Flaw of original Opel mech is that both cables go to bottom, which is a hard angle to follow.
- Honda Accord openers both go to bottom, hence the Civic ones which form a bow-shape instead are maybe better. They're also close to the correct length.
- Using the actual slider seems to be abandoned. Even the Civic ones are a couple inches too long and arch is wrong and the attachment points are wrong. So instead you remove the slider from the donors and mount the motor and cables to the original slider mechanism.
- It might not actually matter what regulator you use because of this, I think this might be Xerox advice where each person copies the person before but have lost the context of why. Like the recipe that tells you to cut the chicken in half before putting it into the roaster, you eventually discover is because grandma's roaster didn't fit a whole chicken, it has nothing to do with improving taste, spice coverage, moisture, etc.
- The cables end up getting cut anyway (do not let them go loose, hold them with tape or they'll tangle in the spring mechanism) and then just clamped into the Opel slide mechanism.
- Opel GT windows get very tight towards the top. These little motors are weak and barely get the job done. Doors are often crooked without you noticing. The rubber sliders that the glass contacts is adjustable and many people don't know this. There is a procedure for this to help if needed.
- Maybe you should just get motors from bigger vehicles with heavier windows instead of Honda Civics, since the slider and cable length no longer actually matter, no one has ever re-used the slider mechanism anyway.
- These things are no cheaper from a junkyard than they are brand new. So just buy new ones.

- Quarter-panel automated window openers. From 1996-2000 Dodge Caravans. Or, 2000+ Caravans, but they'll be backwards so you'll have to flip left and right.



Nothing fancy to access them either just yank the plastics out. Two 10mm bolts hold the actuators on. $5 apiece at my junkyard.

Caravan switches are lighted switches, DPDT momentaries. Mine were $15 for the driver's assembly and $5/switch for the passenger. $15 extra for the wiring harness (I should have just cut it off a few inches after the plug, would've been free).

Many vehicles have shielded, press-fit rubber connectors to the doors. Caravan ones kinda suck, they're very short. The Civic ones were quite long, comparatively. Didn't look at enough vehicles to recommend or buy any particular one for being a good match to the GT.
 
#105 ·
Because you need it :p

I asked. Guys have lost boost and said it's terrifying.

If I was designing it to not use a booster, maybe I would skip it, but from what I understand the master cylinder would have to be different, to deal with pressures that my foot can apply.

I think we went over this earlier in this thread somewhere :p

Electrovair said:
Who would you be cheating if you took the midnight machine shop option? You're not cheating me. If I had access to a machine shop and CNC tools I would be overjoyed.
I think I wrote about it earlier. I recall from my childhood, resentment from seeing "simple" projects on TV that took thousands of dollars of dedicated tools to make.

Part of building it is a challenge, so, just throwing money at one of the most challenging parts, or, throwing expensive tools at it is... I dunno... anti-inspiring? And not that my goal is entirely be inspiring, I just want a fun car, but I recall my resentment towards others for accomplishing things only because of their resources, not their resourcefulness.

I get that you'll get lonesome for it after you're done but seems like a small price.
No, it's worse than that.

I tend to be an all or nothing person. And for the years I was involved there, every piece of machinery was moved and set up by me. Every worktable. Every policy. Every improvement. Probably 80% of new people that joined got their tour and introduction from me. Anytime there was something to do, if I didn't do it myself I tried to be part of the group that did it. We quintupled in size the time I was there. It was a big part of my life.

I miss it, I miss my friends, I miss helping others on their projects, I miss teaching, I miss being a part of it. But, it's not the first place I've volunteered, and it tends to follow a similar path. When I'm volunteering, for the years I'm there, I never get around to doing personal stuff. And, I can't spend all my time there, I work 7 days a week, 12+ hours a day, because I tend to toggle 100% on or 100% off. I'm miserable with hour-by-hour work:leisure balance that most people have, so my work:leisure is binge-based, a few years at a time. Even on a social scale, people that know me know it's normal for me to be really social for a few months, and then drop off the map for a few months and talk to no one, back and forth.

There is zero chance of me showing up and not getting sucked back into being there, or being miserable because I'm not there more often.
 
#106 · (Edited)
Small bits of progress. Haven't been in the shop much and when I do go I mostly sit around and am not sure what to do. Procrastinating, finding other things to do. Pulling parts at the junkyard for other people's vehicles instead of my own, working on theirs instead of mine.

I think I've stalled on the coupler for as much time now as I spent welding the two whole bodies together, still without a good solution.


Coupler Progress:

I made a new spline mold, V2. Used up the entire rest of the silicone tube, figuring I'd used half of it the previous time. Oops, nope, I had enough for the new mold and a tennis ball amount of excess. Oh well. Nice thick walls.



Detail is not as good as V1. I think I overdid it on the corn starch. It has a sandy texture to it. And it didn't release on the bottom of one spline:



Not a big deal, it means my plaster will have extra material, and I can use a knife to shave it back to the right size.

Plaster copies came out okay, few bubbles. Tried vibrating them out using a surplus, err, back massager from the night table, only moderately effective:



Melt-wise... I thought I had lots of cast zinc, pounds and pounds of it. I tested it by leaving little slivers on a stove burner and seeing if they melt. They did, but larger pieces would not. I have aluminum, not zinc or Zamak. I think I want Zamak (almost as strong as cast iron, self-lubricating, stovetop melting temperatures), so now I have to find or buy some from a scrapyard. If not, I can't stovetop melt aluminum, I'd need the furnace.

And knowing I'd be pouring the whole coupler at once, I was worried about having enough battery capacity for the arc furnace. So I called NAPA and asked if I could buy some of their core batteries back for the price of the core. They said sure, and will even let me drop them back off when I'm done and get my core back. Renting batteries for free I suppose.



Out of the 8 I bought, I think 5 were still good. Furnace-wise I think I'm good.

Crucible-wise, I'm waiting for the thrift stores to re-open to pick up a stainless or cast iron pot (and maybe some zamak bathroom fixtures to melt).

I guess I've never even taken a good picture of what I'm trying to do.



I have to do some modification to the transmission output shaft, but how far I turn it down I'm not sure. One consistent diameter. If the motor shaft protrudes 2", I guess I should have 2" of grab length on the transmission shaft. But in my head, the tail housing and motor were almost touching. now that I look at it, they're separated by 4". So, now I need some giant case to enclose all of it, not just a mating plate.

And at that point, am I even saving any weight or length compared to having the whole transmission?


Lots of seemingly-little thing I need to figure out how to actually accomplish. Usually I make progress by just picking one thing and heading in that direction, but there's so many things that all have to be right at the same time:

- To make the coupler, I now have a plaster form for the motor's side. I don't have a form for the transmission side, which could just be a tube, but it has to be the exact size of the transmission shaft, which I should grind down first.

- Then, how do I grind it down consistently without a lathe? Just bench grinder with angle iron to keep it square?

- If my hole on the transmission side of the coupler is wrong, do I have a drill bit big enough to enlarge it? Do I have a chuck large enough to hold it? How do I keep it perfectly centered?

- When I'm making my casting and connecting the plaster splines to the plaster tube, how do I make it centered within driveshaft-required precision (I presume at least 0.001")?

- Can you combine a splined coupler with a taper-lock coupler, or is that going to create too much of a stress riser wherever the slot stops and encourage it to split?

- I haven't even tested if the motor works yet. I haven't finished wiring up my inverter to test it. All this work might be for a motor that I end up not using.


I think the best thing to do is perhaps make the coupler with *only* the motor side. The rest of it where the transmission shaft goes will be temporarily solid.

Then I can slip the coupler onto the motor, and just use the motor itself as a lathe. I think I use a scribe to find the exact center, then center punch it, center-drill it, then set up some books under a cordless drill (flipping pages is a 0.005" adjustment). A still drill bit should be self-centering on a rotating shaft, I think? It'll pull itself perfectly through the middle?

As usual, everything is more complicated than it seems. Tempted to just go back to welding the shaft and being done with it.


Misc:

Brake lines and fittings arrived. Went with the teflon coated one because it was the only 3/16" line on Amazon Prime. $17 line, $13 fitting.



Snuck in at the tail end of the Covid sale at the Opel shop for about $100 of stuff:
- Door bumpers
- Hood bumpers
- Steering rack boots
- Master cylinder reservoir seals
- Master cylinder hose
- Rear transmission seal
 
#107 ·
I haven't checked all of your post for this option. If the outside diameter of the splines on the motor shaft are machined true, you might be able to fit a taper bushing coupling (such as a Taper-Lock design) directly on the splines. The bushing housing could have a flange that would bolt-up to a flanged yoke of a U-joint. The splines could(you would have to check for this) provide enough "bite" into the bushing so a key and keyways would not be necessary.
The flanged housing could be made from a taper bushing chain sprocket-new or used. Some machining would be required to match it and align it to the U-joint yoke flange.
 
#108 ·
The bushing housing could have a flange that would bolt-up to a flanged yoke of a U-joint
I can't go right to the U-Joint.

1 - I can't get the motor that far back into the trans tunnel.
2 - I would like to use the existing speedometer, which runs on a worm gear in the tail housing of the transmission.

But, it's an option to just get or make or modify the driveshaft. Someone mentioned it's only about $100 to show up at a driveshaft shop with the pieces and tell them what length it needs to be.
 
#111 ·
I bought a GPS speedo - eliminates all of the issues - not actually legal but I found one that did not say "GPS" on the front so nobody knows
Yes, but I like the original speedo. I like mechanical and electromechanical things.

My favorite thing about the GT is the manually operated flip-out headlights. No actuators, it's a lever you have to slam into position.

https://www.youtube.com/watch?v=KpPM6NyY6Bc

electro wrks said:
We're just concerned that in your drive to get back to basics, the next step will be all of the work of prospecting for copper or zinc ore
Are there zinc deposits near me? I called today and can't find a scrapyard that takes zinc. Let alone one that'll sell to me.

The only silver lining is that I do actually enjoy these tangents, just not when I have a goal of getting my car done. I've wanted to do EDM and casting for 10 years now.

Also, have you accounted for dimensional shrinkage as the metal casting cools? Most metals expand and contract at a pretty high, but predictable, rate with temperature differences.
Well, the mold is going to be solid, so, it would have to crush the mold in order to shrink down on the internal diameter. Outer diameter I don't care about.

Normally when casting you have to pour extra, as the metal cools it will suck in from that extra material and make a dimple. Since I have an open-faced mold, it's not a big deal, I'll just make it a bit taller than I would have otherwise (or maybe not, who knows, I'll see how the first pour goes).
 
#110 ·
Or drive a speedo set-up off the non-drive end of the motor, if it still has the shaft exposed.


We're just concerned that in your drive to get back to basics, the next step will be all of the work of prospecting for copper or zinc ore and smelting it for your casting operation.

Also, have you accounted for dimensional shrinkage as the metal casting cools? Most metals expand and contract at a pretty high, but predictable, rate with temperature differences.
Years ago, I watched some casting pattern makers go about their job. They had this amazing array of measuring tools to use for making casting patterns for various metals. Each measuring tool had is units of measure adjusted to compensate for the cooling shrinkage of the cast metals they were working with. This saved them from having to make a bunch of shrinkage compensation calculations for each pattern they were making.
 
#113 · (Edited)
Or drive a speedo set-up off the non-drive end of the motor, if it still has the shaft exposed.
That's an excellent idea for a single-ratio drive system like this.

A mechanical speedo drive might be difficult to arrange, even though theoretically possible. An electronic analog speedometer runs on electrical pulses (like a tachometer) and can be driven from a pickup on the motor non-drive end (if exposed), the shaft within the adapter housing, or even the pinion shaft of the axle. It's not mechanical, Matt, but you're building an electric car... ;)

It should be obvious, but since the motor speed is proportional to the road speed, and the motor controller knows the motor speed, the controller should be able to drive a speedometer. It's the same thing as the tach drive, but with different calibration. A stepper motor could even turn the speedo cable from a tach pulse train with a suitable driver.

Remember the concentric gauge setups, with the tach and speedo as inner and outer meters on a common axis? Maybe only the Honda Prelude had it:

With the fixed single drive ratio, you don't even need two separately driven pointers - a single gauge can be marked with both motor RPM and road speed. The RPM marking are redundant anyway, so the tach face could just be marked with road speed instead of RPM. Will the car have the stock tachometer, and if so how is it to be driven?

I just don't see much point in putting a bunch of effort into supporting a separate speedometer, unless original instrument panel look is for some reason very important.
 
#115 ·
I'd previously thought my rockers were rust free. Until I poked at a spot of rust in the footwell and discovered structural paint. A bit more poking opened up a gash on each side. Right at the start of the door. There was a dice worth of foam or something plugging the drain channel, and it had rusted on either side of that plug.

So... now I wonder, what happened inside the rocker? How bad is it?



I have no context, I'm not sure if that's bad or not.

I went about half way in.

Not sure what I'd do to clean it either, maybe some fish tape or maybe drill it out and try to stuff a wirewheel in there. Maybe plug the drains and fill it with Evaporust? Maybe just hose it with primer?

Can't clean out the rocker panels without some kind of rod and room to insert it, so, front suspension has to come off. Also, it's the last thing on the car I haven't disassembled yet so, why not. New steering rack boots are in the mail soon anyway.

Spent the day doing some editing, no graphics or voiceover, but, not much to say anyway:



Few things:

- I eventually realize there's nuts below the cross member mounts.
- I eventually figure out that when you're wrench on one side, socket on the other, put the wrench on the side so gravity keeps it put rather than pulls it away.
- Immediately afterwards, no room for a socket on those front nuts. Barely even room for a wrench.
- I wasn't using either of my two big impacts because it was 3am and the neighbors had their motorhome parked across their driveway and power run to it, so I think they had company staying over.
- Second bolt was badly bent, not my doing.
- Fourth nut was a 17mm instead of a 15mm, just to make things difficult.
- There are spacer-like things under the mounts. Authentic or necessary? Hmm.
 
#116 ·
Order arrived from the Opel GT supplier in the US. My shopping cart had a few hundred worth of stuff during their Covid sale, but it paired down to $58 by the time I ordered. I expected shipping for 1lb of little things from the US to be like, $10 at most.

I guess I wasn't really thinking, I don't need any of this stuff now and the savings from the Covid sale (after I pared it down) were completely swamped by the shipping costs of ordering now.

Even combining shipping with someone else local, a 4lb box was $48 (US) shipping + $18 CAD in duty. $80 CAD to ship 4lbs to Canada. At least we saved money by splitting that to ~$40 each, but, ugh. This is why many Canadians just ship to the border and then go pick it up themselves. If you don't mind the drive, even small orders cost as much as a tank of gas.

Anyway, mmmm, the smell of new rubbers:

- Steering boots
- Master cylinder reservoir seals
- Master cylinder tube
- Door and hood bumpers
- Transmission output seal



Also, I did a little comparison between the window regulator motors for Honda Civics vs. Dodge Caravans.



If you exclude the bearings and the end caps and all that and compare the actual motor (where it gets its power), the Caravan is about 150% the power of the Civic. So I might swap civic ones for Caravan ones (or any other cable-driven regulator, those are just the two vehicles I've been taking apart lately).

This might also mean it's geared differently and just moves faster rather than more powerfully, but, meh. Either was, beefier motor.


Aluminum Coupler:

- Now that I'm trying to pour a beer-can-sized amount of metal, (verus the golf ball sized amount of copper before), I can't just use firebrick.

- That's annoying, because I don't want to order a graphite crucible just for this little project. I need something cheap that'll hold together above aluminum melting temp.

- I settled on a stainless chaffing tray. This kind of thing:



- I melted some aluminum into it, but the metal was so thin, every time I accidentally bumped the sides with the torch it burned a pencil-sized hole through. Also it had trouble holding temperature. I ran out of battery juice before I had much melted.

- I made my first green-sand mold by mixing sand and ground up kitty litter, packing it into a flower pot around an aerosol can for the shape, and then set my plaster spline at the bottom. Wait, is aluminum heavier than plaster? Is the plaster thing just going to bob up through the metal like a cork? Hmm. Too lazy to anchor it with a bolt.



- I called up my fire extinguisher guy and asked him if he ever has old extinguishers for disposal. He said sure and dropped off a handful. The steel is thick enough that it makes good crucibles.



- I chopped the slimmest extinguisher in half and set it into a coffee tin, filled the sides with sand. Hopefully to give it enough thermal insulation to hold the heat. Melted a bunch more aluminum, but still ran out of juice.



- I noticed the can took like an hour to get hot, so I thought, what if I pre-heat the whole can/sand/crucible on a stovetop for an hour or two first, so that it's pre-heated and won't drain batteries. So I did that.

... and it worked!

Sort of.

Problems:

1 - Normally in a combustion furnace you have gas, or CO2 from the burnt fuel. This sort of replaces oxygen. That's good, because oxygen bonds to the molten metal and creates dross, a waste that has to be scraped off before you pour.

Also, the temperatures are low, 3600'F max for propane (and less by the time it touches anything). The hotter the temperature, the more aggressively oxygen will bond to it.

Also, with a combustion furnace you heat the vessel, not the material, so if a layer of oxide forms above the pool, that's okay.

Also, you heat from the bottom up, so it all melts.

With a carbon arc torch, you have regular air everywhere. You have 36,000'F (!) plasma. You heat the material itself, by conducting through the material, the surface of which is already corroded and doesn't want to conduct so the arc keeps going out unless you poke or stir it, oxidizing a bigger and bigger surface scab of waste material. And, heat has to work its way down via conduction, so the bottom is solid and the top is liquid.

All this adds up to mean that the amount of material wasted is like 30% of what you want to pour. You have to scrape it off right before you pour.


2 - I didn't realize how vacuum-packed sand would get around a smooth steel crucible. I used up every last bit of energy in the batteries melting as much material as I could, to as high a temperature as I could. Finally I'm ready to pour, I scrap the dross away, grab the crucible with pliers... the whole coffee can lifts up. I can't shake it loose.

I end up having to stab the sand with a screwdriver a dozen times to make it let go of the crucible. Meanwhile the lid is off and it's rapidly cooling.

I go to pour, and it's just barely at the melting point now. I dump it into the mold, which boils off a little steam inside the liquid metal, cause it to belch upwards to vent. The top of the molten metal collapses down after the air releases, then belches again. Up then down. A third belch... and it only goes part way back down. The metal is solid.

I tried to add more, just so the weight of the incoming metal would pop the bubble and fill the void, but, the bottom 1/3 of the crucible had turned solid.



The casting filled the mold pretty much to the brim, more than it needed to.

So, I broke out the casting and inspected it. Somehow I never took pics of this. I could tell the balance point was almost exactly at the end of the gear splines, which meant the air bubble on the "solid" half must have been almost the size as the whole splined area.

I cut the top off the "solid" end and revealed...



:/ Yep.

Giant air pocket.

I don't think it's a good idea to just pour more metal into that hole, I think you generally have to cast everything at the same time. You can even see there's a couple layers on top where it burped and froze.

Not bad for a first attempt.

Flipped it over cut the rough sandy texture off, and had a good look at the splined side:



... not bad!

The edge needs to have a taper filed into it, it's still got the saw burrs.

Measuring, it's about 0.003" smaller than the motor shaft. Meaning... must still have some crust on the edge interfering with my calipers, or, it's actually slightly small.

I was able to hammer it on 1/4" pretty easily, letting the motor splines shape the coupler's splines a little bit, but I'd rather not be hammering on the motor.

As a proof of concept, I'd call that a success. This looks to be technically possible to do with aluminum.

...

Zamak Coupler:

- I hate aluminum. It's scummy, surface is crummy, it oxidizes badly, it's weak. It melts at a high temp. I don't want it.

- Die-Cast Zinc/Zamak is as strong as cast-iron, surface finish is great, it pours well, it doesn't oxidize badly, and it melts at stovetop temperatures apparently.

- I rounded up every bit of die-cast zamak I could find. Conduit couplers, bathroom towel rod holders, some V-pulleys from a treadmill CVT, some plumbing fittings, a 2-hole punch, railing brackets, chainlink fence toppers, etc. I might barely have enough zamak to make this work. Hard to find, it seems with improved technology, lots of stuff is cast aluminum these days.

- Bought a cheap fried-egg-sized cast iron pan for a crucible and tested whether zamak actually melts at stovetop temperatures.

- Just barely... barely... on my little portable electric burner, but it does. I test-melted as much zinc as I could fit in that little pan (about 1/3). Seems to work.

- Dumped the zinc into a steel pan to make an ingot for the next time I melt. Zinc is 3x as heavy as aluminum so, I don't trust the plaster spline thing to not cork up without being anchored.


...

Next up, more sand, another mold, and an attempt at a zinc coupler. I'd like that to work instead of aluminum if possible.
 
#117 ·
Zinc has an even greater(~1.5X ) rate of thermal expansion compared to aluminum: Thermal Expansion of Metals
So, with your current casting technique, you will cast an even more useless chunk of of metal. You were warned about this problem in a previous post. This was probably figured out ~ 7000 years ago when the first castings were made, and compensated for. You really should do more research on subjects before you waste people's time with your flailing around.

All right, I chewed you out enough. One way to compensate for the shrinkage might be to dip and dry the male spline plaster core piece in watered down plaster (or a more heat resistant material), to slightly build up the size of the core.
I'm not sure about best casting techniques for zinc. With aluminum, the molten metal should be degassed in a vacuum or chemically, and the mold filled from the bottom up. This reduces the porosity and.voids
 
#118 ·
You really should do more research on subjects before you waste people's time with your flailing around.
You dont have to read his posts if you dont want to.

This whole project does sort of seem like an elaborate justification to just play around in the shop; which I totally understand. It does seem to me though, that the constraints you have placed on yourself are going to preclude you from building a functional vehicle. At least in the sense that it will be a dependable little around-town car. I feel like the best analogy I can come up with is that you are trying to MacGuyver an EV. Bubblegum and paperclips can only do so much.

I am very curious how long a motor adapter made of melted-down brik-a-brak could hope to last. Pot-metal is not a material famed for its strength, and there is going to be a lot of torque applied to those splines.
 
#120 ·
I may be way off base, and I confess my only knowledge on the subject comes from what I read on wikipedia.

Pot metal - Wikipedia
"There is no metallurgical standard for pot metal. Common metals in pot metal include zinc, lead, copper, tin, magnesium, aluminium, iron, and cadmium. "
"The primary component of pot metal is zinc, "
"Pot metal is generally used for parts that are not subject to high stresses or torque.

Part of me really wants the idea of home-cast adapter to be a viable solution, and since it does seem like you are having fun, by all means, carry on! If it works, I will be impressed. Is the idea to machine down an end of your casting to mount the flywheel?
 
#122 ·
I may be way off base, and I confess my only knowledge on the subject comes from what I read on wikipedia.
Hmm. "Pot metal" is just a derogatory term for "throw in anything that's left over and melt it". So it varies.


Zamak on the other hand is a controlled mixture, is nearly as strong as cast iron and is self-lubricating.


If I add a little bit of copper (1%) and a little more aluminum (a couple %) it's becomes even stronger and harder.

Is the idea to machine down an end of your casting to mount the flywheel?
Nope. Join motor shaft to transmission output shaft.



That's just the little tail housing on the transmission, it's about the size of Coke bottle.

I'd be tempted to use a blueing technique using permanent marker against the motor spline to get the fit just right, once you have successfully poured your coupler.
I might do that if I have to machine it manually. Not worth a lot of extra effort in the mold making stage to get it perfect.

It's not that much effort to just adjust the shape afterwards. There are 25 splines, there are 4 faces on each spline (peak, valley, left and right sides), I might have to remove 0.003" from each face. A little bit of filing with a key file or a piece of sandpaper wrapped around a hacksaw blade. Just go around in a circle until it's done. Same thing they do with dentistry.

Considering the motor shaft is hardened steel and the coupler might be aluminum or zinc... if I could support the ass end of it and not be hammering on bearings, I'd just squirt some cutting fluid on it, use the shaft itself as a perfect broach and hammer the coupler on and off until it was clear. We're talking chips thinner than a sheet of aluminum foil.
 
#121 ·
Matt I think you are doing great things, and yes as much having fun and learning and doing it your way. Take others' comments with a pinch of salt. If they can't be supportive or at least courteous they should mind their own business.

I'm impressed with your approach and pragmatism to your build and hope you make it to the finish line. I'm sure you will and it'll be a better build for it too!

PS the casting is looking promising. Better too much material and you can dress it back than not enough. I'd be tempted to use a blueing technique using permanent marker against the motor spline to get the fit just right, once you have successfully poured your coupler.

Cheers
Tyler
 
#123 ·
No news like bad news...

Took a close look and noticed some funny coloring on the driver's side.



Trouble is... in the area I know to be bad, I can't visually identify it with the scope. So for all I know, most of it is that bad.

I only lightly chain-whipped the outer rocker, pretty hard to get any kind of movement with a narrow triangular cross section, but, maybe better than nothing. Looks like lots of debris knocked loose, but, I didn't chain-whip the inner and it looks exactly the same so maybe not.

Looks like I'll need to patch significant portions of both wheel panels on both sides in the rear, and probably the rearward portion of the front wheelwells too. I expected a couple small patches, looks like I'm in for 6 medium sized patches, and I get to discover how applicable my trigger time welding up the interior is going to be on the exterior where it'll be visible. I predict.... not well. Have a feeling I'm coming on a turning point of a project I can finish, to one I never will.

Rockers on the passenger side don't look as suspicious as the driver's, but, I'll give them the probing too. Not sure what to do about those. Maybe plug the ports with hot glue and fill them with another gallon of evaporust. I suspect the paint is structural in many places, I'll leave a plastic sheet underneath so I don't waste all my evaporust when it escapes. And then, who knows what's left in there.

Rather demoralizing, especially for my first day back working on it after several months, and having wasted all the daylight hours of the summer on other people's vehicles. Back to working under bulb light. Probably has to be fixed to pass out-of-province safety too.
 
#124 ·
Matt - there comes a time in every project

I think you need to either get the whole shell blasted and start again

Or simply start again

Have you looked at the "Locost" ?
It would probably be quicker and easier to make a Locost chassis to take the Opel running gear
 
#125 ·
Have you looked at the "Locost" ?
It would probably be quicker and easier to make a Locost chassis to take the Opel running gear
Perhaps, but it would make little sense to use the Opel running gear without the Opel GT body - the body is the point of this vehicle selection. If building a tube frame special, there are many more suitable donors of suspension parts.
 
#127 ·
Well, did some more digging into the rust. Two weeks ago. Trying to stay motivated.

For those that enjoy sped-up rust pokin' 'n proddin':





Few notes:

- Driver's Rocker isn't in great shape, but appears to be worst just in a diagonal line. My guess is that it was parked outside, with the tail lights removed, on a driveway or hill, until dust settled. Annual Arizona rain rusted a single line through the metal there. The interior rocker has holes at the back but otherwise isn't too bad. I see a line of paint bubbles that seemed solid when I poked them but I'm thinking have to be where the rust bled through to a pinprick. Maybe best to just replace an extra 6" down that line.

- I don't know what those white goopy knobs are inside the driver's side rearmost fender, but, I'd suspected this car was rear ended at some point, lightly. Looks like those might be the scabs from dent pulling? Isn't obvious to me from the outside.

- Passenger side isn't nearly as bad, half the damage. Doesn't really matter, a slightly smaller or larger circumference doesn't add too much time, and the damage is mostly in a single plane so no complex curves, low enough that the wheel flares haven't sprouted form the side yet.

- Passenger rocker has no holes at all that I found. Rust spot is from the outside where paint wore off. Camera scope picks up a couple rusty patches inside, but otherwise looks great.

- Front wheelwells and fenders seem intact, couldn't poke a hole anywhere. So damage is confined to the ass end and the driver's rocker.

I'm not even sure where to buy sheet metal from affordably. Had an idea to just take a sawzall to the junkyard and cut the roof off a minivan or something equally sheet-esque. Then I wondered if the metal on a new car is more likely to be paper thin compared the GT. Maybe should try the side of a truck box instead. Maybe older is better? Will have to do that soon, summer is over, fall is here, snow arrives soon.
 
#128 ·
Matt
I have been there - you need to handle rust as a zero or 100% - you are going to do a ton of work - and then nothing

Rust is horrible

Either blast it down to bare metal and paint it immediately - as in within the hour - or it will do a zombie and come back at you

I have a horrible prediction that you will make a half decent car and it will then fall apart in front of you
 
#130 ·
Finally made a go at casting with Zamak, after my first attempt struggled to maintain high enough temperature with aluminum.



Stunning partial success:

- This is a great way of turning $300 of conduit couplers into $3 of zinc.

- Best cheap source of Zamak I found was in old 2-hole punches. Just had to rip them apart and remove the steel punches and springs. They were a pound and a half each. Towel racks, cheap chromed drawer knobs, banister supports, and a CVT pulley from an old treadmill were all also Zamak.

- Zamak weighs 2.5 x as much as Aluminum. My previous attempt that got the giant airpocket frozen into it was 404g. If that was filled solid it would probably be 40% heavier. All told, I'd need at least 2500g (actually, bad math I notice now, I calculated as if missing 60%, not 40%, oh well). Turns out I had around 4kg of the stuff, so, should have been plenty even after the excessive dross of melting it in a frying pan.

- A heavy duty stainless steel frying pan is not strong enough to lift 10 lbs of zinc. Had to use pliers on the far side to help

- Missed the sprue, sloshed over into the main pour.

- Zamak is 2.5x the weight of aluminum. Buoyancy on that plaster form is now 2.5x as strong. Up it pops like a cork. Nothing to do but finish the pour and spend 2 hours melting it down again. In retrospect, this is like filling a bathtub and expecting the tennis ball to stay at the bottom.

- Form seemed relatively undamaged by the pour, so for shits and giggles, I stuffed it back in the topside, just guessing at where the center was and the correct angle.

- I hit pretty close to center. I hit pretty close to square to the surface of the pour too... except that the mold wasn't square.

- I probably destroyed the motor bearings, but I lightly hammered the coupler onto the motor, and then pried it back off a half-dozen times. The hardened motor shaft is taking just the slightest shavings off of the surface on a half-dozen splines. It's already 2/3 of the way on, I won't press it further until I have a slide hammer or some way of getting it off, it's too deep into the recess to pry it out if I go deeper.

- Surface of the splines seems as good as they ever were in plaster. Zamak is famed for being a zero-machining process, you can capture the surface of a coin accurately if you want, so all imperfections were silicone/plaster based. It's good enough.

- All the excess chunks I cut off showed solid metal all the way through, no porosity.

- The coupler being off-kilter isn't a big deal. It doesn't have to be a 1/2" thick, and certainly won't be at the transmission end.

Overall, Zamak was beautiful to cast with. Stayed glassy smooth for several minutes (off camera) after the pour. I'll have to keep an eye out at the junkyards for old bathroom fixtures and such.

Plan now is to get the motor spinning, and use it with a grinder as a lathe to make the coupler centered on the motor shaft. Then drill it out for the transmission shaft (a drillbit on a rotating workpiece is self-centering... supposedly).

Also, there's an air cavity at the bottom of the splined area, probably from gas escaping from the plaster. It's not critical, and once I have the hole drilled for the transmission tail shaft, I can gouge the sides and repour some zamak just to give it a helping hand and fill the gap, even if it doesn't add much for strength.

.
 
#134 ·
This car is a LOT of work!
I was going to have my first conversion be something simple and lame, like a '94 civic or something. Dead simple, easy to swap, be done with it. Then do a car I was more interested in driving.

But then I discovered what car I really wanted to convert, and one came up for purchase, cheap, almost immediately, so, I got thrown into the deep end a bit on car restoration. Without even having a shop to work on it.

Its been a while since there was an update. How is it going?
I haven't worked on it in 8 months. I was procrastinating on some other big things I needed to take care of, so I figured, I'll put the car on pause and stop avoiding one type of work by doing another type.

Fast forward 8 months, I haven't worked on my car, but I also haven't done any work on the other things that need doing.

Also, Covid put a bit of a wrench in the works, I needed a transmission from the local owners club, but, didn't want to take risks with any of them hauling it out of the parts barn, which was also snowed in.

So, only update is that last week I got a transmission and bell housing, and have to make some choices about just how much of it I want to keep.

Also, my tools got stole a month ago, along with my commuter vehicle, so, that didn't help. Still trying to find out what I'm missing.
 
#137 ·
First update in a while, before I catch up, a question:

I want to use an iBooster (electric brake booster). I found some Gen1s for sale.


( Full unit )


( Just the booster, no MC/reservoir. )

Lots of these are sold without the master cylinder. That's okay, I have a master cylinder for the GT, already rebuilt/refurbished.



What do I want?

Do I want to save myself an extra $100 by not using the Bosch iBooster's master cylinder, and somehow plumb my proper GT master cylinder to the electric brake booster? Since the MC is designed for the brake system on the GT (is it?)? Or, do I want to spend that extra $100 and get the MC that belongs to the iBooster, but does not belong to the GT?

I'm redoing the lines anyways, so that's not an issue.

I presume the connection to the MC can just be any hydraulic fitting? And maybe slap a bracket there so that it stays put? I don't have much knowledge about brake systems.
 
#138 ·
Do I want to save myself an extra $100 by not using the Bosch iBooster's master cylinder, and somehow plumb my proper GT master cylinder to the electric brake booster?
The iBooster boost unit isn't "plumbed" to the master cylinder, because the booster is completely electromechanical, with no hydraulic component. As far as the plumbing is concerned, there would just be the stock master cylinder (maybe positioned differently). What the booster does (like a vacuum booster) is add push to the rod from the pedal.

... Since the MC is designed for the brake system on the GT (is it?)? Or, do I want to spend that extra $100 and get the MC that belongs to the iBooster, but does not belong to the GT?
It probably depends on how readily the GT's master cylinder will work with (mount on and connect mechanically to) the iBooster. The GT's master cylinder will have the right size of bore (at least for the stock car) and ports that work with fittings matching the size of brakes lines in the car.

I presume the connection to the MC can just be any hydraulic fitting?
No. There are many styles of hydraulic fittings, and you need to match the master cylinder ports. They are normally flare connections (line is flared and nut around line clamps flared end into port), but there are various sizes and styles of flares. With any luck the GT has common double flares, but it's likely a metric line size.
 
#139 ·
Look at what brakeline fittings you need, in detail which includes ordering & testing them, before you decide anything.

Using the iBooster master may involve unobtainium brakeline adapters you'll need to custom make.

Using the Opel master also means custom design & machining of the mount and pushrod if you use the electric booster.

For my C5....vacuum pump. Good enough for production Caddy & Malibu, good enough for me. Got bigger fish to fry.
 
#148 ·
Same same.

That OEM booster relocation setup is merely Germans efficiently euthanizing drivers that survive being impaled on the steering shaft.
There's still another 2 feet of car past the end of the hood. I dunno that I'm overly concerned with safety during the crash as I am prior to the crash, but considering the lack of airbags all I've got for safety is distance between me and the very-much-cosmetic-only bumper.. I'll take any bonus safeness.

my device is 805 kg - so not really half the weight!
Hmm, I thought you were a lot lighter than that. You're right, that's pretty close.

Your legs need to hold you up when you walk - and accelerate you when you run or jump so they are strong enough to easily push 100 kg for a small guy
I biked everywhere before I learned to drive not that long ago. When skinny jeans were in style, I couldn't even get my calves past the thighs.

Another issue is insurance. To say I removed powered brakes might not be appreciated if it ever comes up.

the sound is reassuring
I'll still have an e-brake. EVs are annoying enough with weird noises. The motor and inverter are the ones that scare me but I'd rather the vac pump not be on the list.

...

Back to topic, fabbing my own mount for the master cylinder to an iBooster? Simple, or foolish to try?
 
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