[toddshotrods]

Originally Posted by Woodsmith

I can still see an issue with both the sets of sprockets being perfectly in phase. If one sprocket was a degree out of line with the other on the same shaft then the leading one would take all the load and the trailing one would probably just make noise and whip about until the loaded chain stretched. Having a tensioner would solve the whip but wouldn't resolve the phasing issue. It could also cause some torsional vibration in the jackshaft...

Sorry, I confused the issue with my reply. I attempted to agree that it would be best to let go of my obsession with symmetry and drive the jackshaft from one side of the motor. The tensioner sprockets I mentioned, "on one of them" was referring to either the drive chain from motor to jackshaft, or on the chain from the jackshaft to the differential. Actually I like the idea of using one on each of those chains, and not having a sliding or eccentric style tension adjustment.

Originally Posted by Woodsmith

...I would be tempted to keep to one chain to drive the jackshaft and maybe at the other end of the motor have something else to balance the looks...

Exactly. Agree 100%

Originally Posted by Woodsmith

...Mainly because I wanted a specific look of the foot mount appearing to be a cast part of the motor barrel and also because it gave the motor a flat mounting surface instead of a curved one. To make, drill and tap in the same kind of foot to the motor would have been beyond my workshop machinery to make it look right. The foot would also have to be taller to hide the bolt heads underneath.

Gotcha, thanks.

[Woodsmith]

I wonder if you could dish the diff sprocket far enough so that it lines up with the motor sprocket?
The drive shaft CV joint could sit inside it.
You would only have one chain then, or a toothed belt. It could weave its way through the suspension members with the help of a tensioner.

Are you going to reverse the motor as well? Single tensioners don't like being on the drive side. A solution is to have two tensioners mounted on a swing arm so that it allows the drive side to have a straight chain line while maintaining tension.
The ones I have played with have the two tension wheels outside the chain, but joined with a bar, and squeezing the chain inwards. The centre of the bar is pivoted onto a swing arm that allows it to swing up or down so that the drive side is always straight and the slack side is pulled inwards.

[toddshotrods]

Originally Posted by Woodsmith

I wonder if you could dish the diff sprocket far enough so that it lines up with the motor sprocket?
The drive shaft CV joint could sit inside it.
You would only have one chain then, or a toothed belt. It could weave its way through the suspension members with the help of a tensioner...

No chance of that. The lower control arm's front bar runs right under, and parallel with, the axle, and it's mount is on the frame just under the CV joint. Hope that makes sense.

Originally Posted by Woodsmith

...Are you going to reverse the motor as well?...

Yup. Especially since it's going to have the SepEx motor now, and won't require a massive contactor or switch to accomplish it.

Originally Posted by Woodsmith

...Single tensioners don't like being on the drive side. A solution is to have two tensioners mounted on a swing arm so that it allows the drive side to have a straight chain line while maintaining tension.
The ones I have played with have the two tension wheels outside the chain, but joined with a bar, and squeezing the chain inwards. The centre of the bar is pivoted onto a swing arm that allows it to swing up or down so that the drive side is always straight and the slack side is pulled inwards...

I'll have to look into that and play around with the idea. The other alternative is get a bunch of gears and make an enclosed housing...

[Woodsmith]

Now who was it here who did a chain drive from a motor by removing the internal fan and fitting the sprocket in there with the chain fed through the vent holes in the DE cap?

That would move the chain more inboard so you can have a main and tail shaft apparently not driving anything.

[toddshotrods]

Originally Posted by Woodsmith

Now who was it here who did a chain drive from a motor by removing the internal fan and fitting the sprocket in there with the chain fed through the vent holes in the DE cap?

That would move the chain more inboard so you can have a main and tail shaft apparently not driving anything.

I think I remember reading that - was that you?! Wouldn't that make a mess of the field coils and armature, from the chain slinging oil? As cool as that sounds, there probably isn't really a lot to gain as I would still have to drive a jacksshaft to get the main drive chain where I need it.

I told the other design guy on the team about the chain drive and he was all smiles. . I knew he would love it. Chain drive on a crazy car is right up his alley.

[DavidDymaxion]

Glad to see your posts, I enjoy reading them!

You can run a fixed current on the field, and a controller for the armature. A fixed field would mean you could motor (forward torque) below a certain rpm, and regen above that rpm.

• Motoring over the car's full speed range that means a weak field and no regen. Weak field = weak torque, so less fast taking off.
• A mid field current level would allow more takeoff torque up to maybe 50 mph, and regen above 50 mph
• A strong field might be more torque up to 10 mph and regen above that (but that might also overheat the field)

The other problem with a fixed field is you'll have skid-the-wheels strong regen at high rpm unless you do something sophisticated with armature control.



Anyway, if you want real sepex fun you really want to control the field, too. Indeed, I'd say do a contactor on the armature, and a controller on the field would be faster, better regen, and more fun -- but then takeoff would be a challenge (maybe a starting resistor for the armature?).

Originally Posted by toddshotrods

... It also gives me the opportunity to have regen on the front wheels, with the SepEx motor. The controller issue is still relevant, but since there is a limit to how much power one can effectively push through the front wheels, it should be more feasible to experiment with. Initially, I think I can run it with a fixed field current, because of the limited use I have in mind for the whole system.

[toddshotrods]

Originally Posted by DavidDymaxion

Glad to see your posts, I enjoy reading them!

You can run a fixed current on the field, and a controller for the armature. A fixed field would mean you could motor (forward torque) below a certain rpm, and regen above that rpm.

• Motoring over the car's full speed range that means a weak field and no regen. Weak field = weak torque, so less fast taking off.
• A mid field current level would allow more takeoff torque up to maybe 50 mph, and regen above 50 mph
• A strong field might be more torque up to 10 mph and regen above that (but that might also overheat the field)

The other problem with a fixed field is you'll have skid-the-wheels strong regen at high rpm unless you do something sophisticated with armature control.



Anyway, if you want real sepex fun you really want to control the field, too. Indeed, I'd say do a contactor on the armature, and a controller on the field would be faster, better regen, and more fun -- but then takeoff would be a challenge (maybe a starting resistor for the armature?).

Great post David - thanks for the insight. I think you're right. I will plan on a small controller for the field, maybe with some kind of vintage looking lever to control it (via the pot box), initially. Maybe we'll work on our own software to control it eventually...

[toddshotrods]

It occurred to me today that I have never tested the GE 11" SepEx motor. It's so freakin clean inside that I always figured there's no way it wouldn't at least run decently. I decided to give it a spin.

The first attempt had me a little concerned. I hooked a (12v) motorcycle battery to the field with automotive jumper cables, then used the car's (new) battery cables to hook the practically new Duralast (750cca) battery to the arm. It turned tiny bit then the battery cable end started glowing! Realizing I was pulling a LOT of current I literally yanked them off the arm terminals (they were starting to fuse)! I tried to touch them a couple more times but the arc was too intense to even think about holding them there.

My first thought was there must be something wrong inside the motor. The (arm) terminal bolts were pretty warm, but the field coils, and leads to the brushes were all still room temp. Then it hit me - I had trickle-charged the car battery, but forgot to do the motorcycle battery! It was at 7.84 volts!

I hooked the jumper cables to the car battery, and to the field, then touched the car cables to the arm and she purred like a kitten. In the other thread about testing a SepEx I think it was recommended to use two separate power supplies so I just spun it for a matter of seconds and quit. I'll charge both of my batteries back up and let it sing longer next time, and get a little video...

It sounds good though.

[toddshotrods]

Back to work on the chassis and suspension. I'm using Mustang II geometry up front. The Honda Accord knuckles were cut off, machined, drilled, and tapped, to allow me to use a .750" rod end in place of an upper balljoint. To facilitate that, and to stretch the upper control arm to the right length, we're welding short sections of tubing into the stamped steel Honda control arms. A threaded bung will be welded into this for the rod end. Eventually, these arms will be boxed and internally reinforced. I could have just built tubular arms, but I like the shape of these and wanted to play with them.






Now that I've finally sorted out my thoughts on it, there should be lots of chassis work coming up. This is going to be a really unique little car.

[toddshotrods]

A small detail that has taken me forever to resolve, not because it was difficult or complex, but because it was mostly a matter of aesthetics - and I couldn't make up my mind! The front crossmember:

It does have a structural component, as this is what the steering rack mounts to, but the real challenge for me was coming up with a shape that "works". It will be mostly hidden by the grille and steering rack, but I know it's there, and it will be somewhat visible. If it works as planned, it will be one of those subtle details that you don't really notice, that adds something to the whole picture. Like a perfect brush stroke in the middle of a painting, that doesn't so much catch your eye but prevents it from noticing, until you decide to notice.

You might notice in the rendering that I didn't finish the CAD model. I just needed to develop the shape of the top and bottom plates to cut a pattern for them. The edges will be radiused to match the 2x3" tubing; making the frame rails sweep into the crossmember, like it was carved out of one piece of steel. That will all be good old fashioned hand fabrication.