DIY Electric Car Forums banner

101 - 120 of 122 Posts

·
Registered
Joined
·
1,023 Posts
Discussion Starter #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.
 

·
Registered
Joined
·
2 Posts
Hi Matt,

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 get that you'll get lonesome for it after you're done but seems like a small price.
 

·
Registered
Joined
·
1,023 Posts
Discussion Starter #105
Why are you messing with a brake booster on such a lightweight vehicle?
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.
 

·
Registered
Joined
·
1,023 Posts
Discussion Starter #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
 

·
Registered
Joined
·
693 Posts
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.
 

·
Registered
Joined
·
1,023 Posts
Discussion Starter #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.
 

·
Administrator
Joined
·
6,054 Posts
Re the speedo

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

About $50
 

·
Registered
Joined
·
693 Posts
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.
 

·
Registered
Joined
·
1,023 Posts
Discussion Starter #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).
 

·
Registered
Joined
·
4,506 Posts
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
I agree that this is a sensible solution. Here in Alberta (where both Matt and I are), the Vehicle Equipment Regulation (AR 122/2009) only requires that:
76(1) A motor vehicle must have a speedometer that indicates the speed of the vehicle when it is moving forward.
I saw a kit-built car (Lotus Seven style) with a GPS speedo a few years ago; that doesn't prove anything, but the owner had used it for years and not had an issue.

In my motorhome the SuperDuty truck instrument panel is poorly placed for the motorhome driving position, and calibrated for the U.S. market (so the km/h markings are hard to read), and my solution is an ordinary automotive GPS set to the screen which prominently shows speed (in km/h) and mounted in an easily seen position.
 

·
Registered
Joined
·
4,506 Posts
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.
 

·
Registered
Joined
·
4,506 Posts
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.
Matt, you would proabably like the BD-5 kit-built aircraft: it has retractable landing gear, which is manually operated (nothing electric, nothing hydraulic, no power assist), with a big lever between the pilot's legs to deploy and retract the gear. :D
 

·
Registered
Joined
·
1,023 Posts
Discussion Starter #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?

https://www.youtube.com/watch?v=OQtBjQjRFB8

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:

https://www.youtube.com/watch?v=6oYwNkVrTiA

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.
 

·
Registered
Joined
·
1,023 Posts
Discussion Starter #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.
 

·
Registered
Joined
·
693 Posts
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
 

·
Registered
Joined
·
74 Posts
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.
 

·
Registered
Joined
·
1,023 Posts
Discussion Starter #119
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.
That was my idea. If I'm only off by 0.003", (and if what you say is correct, I'll be off by ~0.004-0.005" for zinc), then I only have to add that much by dipping.

However, anyone who's ever drawn ever-increasing sized bubbles around the path of a letter would know that eventually your shape averages out to a circle. Yes the outer circumference would expand, but the inner creveces would also fill in until the splines didn't exist at all. That would be wonderful for clearance, but not so much for grip. It's a double-edge sword.

I've made one too tight, perhaps next time I'll risk making one too loose.

the molten metal should be degassed in a vacuum or chemically
I dumped borox in there, stirred, then swept the dross, which I think is for degassing?

and the mold filled from the bottom up. This reduces the porosity and.voids
Ahh, yes that makes sense, the moisture boiling off would boil off into the air above it, rather than into the metal around it.

I have enough aluminum to do that, but I don't think I have enough zinc to create a pouring cup, downsprue, or riser. I'm right on the edge of having enough even after thinning the walls out.

This whole project does sort of seem like an elaborate justification to just play around in the shop;
How dare you.

It is neither elaborate nor a justification. It is me playing around in the shop. :D

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.
The original splined shaft is about 1" diameter.
The input shaft of the transmission on my large ~300hp 4x4 SUV's transfer case is I think 1.3".
This motor 's shaft is 1 5/8". Which is more than 2x the cross sectional area of the original.
The wall of the coupler is 3/8" thick. It's thicker than the business end of a baseball bat.

Heavy duty enough to be a cannon. I am far more worried about alignment than I am strength.

Also, it's not pot-metal. Pot-metal, or "white metal" is usually tin (and whatever else gets melted down into the pool). Tin is crappy, crumbly and weak. I'm using casting alloys of aluminum and casting alloys of zinc. Zinc is as strong as cast iron.

If it breaks, oh well. I'll curse and swear and weld the two shafts together forever.
 

·
Registered
Joined
·
74 Posts
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?
 
101 - 120 of 122 Posts
Top