Datsun Roadster: 2020 Challenge Build

Something something reverse box something something?

I know why it is happening, and I fully approve, however I don't know the full plan of how and would like to be in on it.

Mr_Asa said:

I don't know the full plan of how

That makes 2 of us!   

Oh crap..  I'm supposed to be the expert here.

In reply to nocones :

Oh good.  I'm at the same level as everyone else involved.

this involves making it a "mild hybrid" using electric assist from a HammerStore drill, right?

Mr_Asa said:

I don't know the full plan of how and would like to be in on it.

me too! 

rough plan is to salvage the helical LSD that should be hiding inside this trans. (trans is from a cobalt SS). 

Then, simply cut off the rear half of the car, fab up new rear end, weld back on, and bolt my existing sprocket to the diff. Do something for axles, rear hubs, springs, consider adding some sort of braking capabilities to the unit. Maybe consider a way to keep some sort of lube inside the diff. I do have a line on some free saturn ion redline axles and bolt-in wheel bearings so I will be doing my best to use those. 

And then repeat at the front end of the car. 

sleepyhead the buffalo said:

this involves making it a "mild hybrid" using electric assist from a HammerStore drill, right?

how many alternators does it take to get to 100 hp?

Apexcarver said:

Something something reverse box something something?

that would be smart. So I'm certainly not doing that. 

In reply to Robbie (Forum Supporter) :

Hey, that trans looks familiar, glad to see it put to use!

Sweet! Progress! 

Almost there!

Ooooh quaife!

Robbie (Forum Supporter) said:

sleepyhead the buffalo said:

this involves making it a "mild hybrid" using electric assist from a HammerStore drill, right?

how many alternators does it take to get to 100 hp?

quick google indicates 50-100 required... without attempting an over-volt; which I'm not sure is recommended/possible?

For others possibly serious about hybrid or mild hybrid, newer ram "etorque" setup is basically an oversized alternator that is also a 25ish hp hybrid motor driving its power assist through the belt drive...  Don't know junkyard pricing on those modules though, but you might find a pick and pull that accidentally prices one as an alternator.

It will be interesting to hear how much improvement you get from the diff. Making mid corner throttle application a bit dynamically smoother should pay off. 

In reply to Apexcarver :

Yeah I like the idea of those "Reverse alternators". Might have to mess with one sometime. Especially since a car like this is light enough for it to make a big difference, and it should be relatively easy to add a belt drive directly into the diff (next to the chain or something).

I'm hoping the significant improvement in this next stage of work comes from suspension compliance and keeping the tires touching the ground after bumps. LSD is a small bonus. Currently the car is incredible on perfectly flat sections, but alas, perfectly flat isn't life.

Sweet! What was the rationale for the cobalt trans, just the cheapest helical LSD diff you could find?

Run_Away said:

Sweet! What was the rationale for the cobalt trans, just the cheapest helical LSD diff you could find?

Well, yes, it was the cheapest I could find. But it also has other significant benefits like: 

1. The cobalt uses a center shaft and 2 short CV axles (same part number for both sides). So without the center piece, it might be narrow enough for my application. I think it is actually the narrowest combination possible with stock parts (I checked Cobalt/ion, Nissan ser, Honda Civic SI, etc).
2. The cobalt also uses bolt on front wheel bearings that I should be able to make work with my 5*114.3 wheels. Cobalt is 5*110 I think but I can likely redrill the hubs.
3. A fwd diff is generally smaller and less massive than a rwd LSD.
4. And it was cheap. Part out was advertised right here in parts for sale last summer, and I took delivery of the trans at the challenge. $20 for challenge car use! Hard to argue with that.

So remember i mentioned I had a line on some free axles and hubs?

Yesterday I went to pick them up. Only catch? I had to remove them from the vehicle myself. 

"Seller" was a true car guy. He has a cobalt SS, so when this ion redline came available to him after it was rolled, he jumped on it to grab a couple parts. He is parting out the rest, but other than a couple key parts he is asking for money for, the rest is 'if you want them it's free, as long as you remove'. Very cool. 

Here is the rolled redline, and here is the parts haul.

In reply to Robbie (Forum Supporter) :

Well done, Sir!

Heck yeah! 

I am very curious how a helical LSD would actually behave without the correct lube in it. The tapered rollers supporting the carrier might survive with a 3D printed TPU seal of some sort and some grease, but some sealed ball bearings can likely be found in a catalog somewhere that would be suitable considering the sprocket arrangement doesn't introduce any thrust loads. 

In reply to bumpsteer :

That's basically the plan.  It will run with light lube in a simple can in pillow blocks.  It will be interesting to see how the Helical Gear diff works without an oil bath   The internet says the tappered bearings have an ID of 1.997 which is VERY close to 2".  Cheap 2" sealed pillow blocks are available that are rated for ~7000lbs of load (EACH) at 3500rpm.  Bearing retainer or a 2.125" ID bearing with machined sleeve should work.    Based on Tire Diamter and expected performance envelop the diff will be below that RPM, and 520-530 chain is typically rated to around 8000lbs.  So it seems for this use case the chain is likely to be the limiting factor.   Assuming the car hooks it would need to put ~6000ft-lbs of torque to the ground to break a chain or damage a bearing.  

That's the Theory anyway.  

I might need a diagram to visualize what's going on here, but it sounds really exciting.

nocones said:

 

That's the Theory anyway.  

So, here's my experience with chains.  I have had several bike engined cars and used good (DID or RK) 530 x-ring chains.  On cars making 180 to 220 hp, I had no chain issues as long as I kept the diff / rear sprocket aligned and kept it from moving around under load.  This was launching on 10" slicks for autocross  / hillclimb.  On the other hand, I had a car making only about 140 hp that would wear chains a lot (had to re-tension the chain after three autocross runs) because the diff carrier would twist just a little under load.  That let the sprockets get out of alignment just a little and that was all it took.  I don't have any experience with the 520 chains.

After removing the cobalt center section, the "hub to hub" distance is about 46 inches, which is a really good width for the car.

Also, here's a closeup of the diff, hoping it's not too hard to "seal" these holes up so grease stays inside.

Not sure if I will use the knuckles or make my own yet.