New Tremec TR-9070 DCT in a SLC?

Bob Winn

Supporter
So here are some sketches I have been playing with. All are done in sketchup, i am doing some more formal ones in fusion360 as I have time. Mostly this was for clearance checking and just to see if the idea is feasible. The chassis is drawn from a 3d scan provided by Mason S. In this configuration you can easily get a large tesla drive in the rear with 18 lg chem batteries. I am showing a "side pod" version here where 6 of the cells run along the passenger compartment. You can also fit those 6 in the mid engine area, but they start to get higher off the ground, this seems like a better arrangement. If I had infinite money I would redesign the engine bay to widen it a few inches as we could better fit the batteries. With the two drives, fully cooled, and with the full pack you are looking at ~1270 hp and 960 ft/pounds of torque, maybe 120-150 miles of range depending how crazy you push it. Gearing it to around 6.5:1 would get you linear acceleration about 80 MPH, peak hp at 115, and a gear limited top speed around 225. Yo could even do interesting gearing, like dropping the rear gear to 7-8:1, and the front at maybe 4.5:1 if you really wanted to optimize for sustained high speed vs acceleration. Drives weight 290 pounds each, pack will weight about 700, you are looking at about 1250 pounds just for the drive and battery, I'm sure you could bring the car in under 2800 pounds, in race trim. I will pull my spread sheets out and look more closely at what I think a sustained top speed would be. I am showing my AWD thoughts here also. I basically add a front space frame out of 2" aluminium, then cover in aluminum panels. The front of the frame is bolt on, you can fit a large tesla unit up front, retaining all original mount points for the suspension, and only losing 4.25" of leg room, which could easily be made up by moving the seat back, as there will be no gas tank behind the seats. I have played with various suspension ideas, and this is the best I can come up with, it gives a 1:1 wheel to shock travel, you could probably add hydraulics to the push rods, or use a lift shock. I have seen similar used on some Ultima's. You will notice that I am removing the inverters for the drives and running them in front of the rear wheels. This has been done at least one other time on a EV conversion. I have some scans of the body work, and everything fits quite nice under the skin. Cooling, not shown on this drawing, is a combo of front mounted radiator, and 3 rear mounted AC loops. Anyway, I have been looking for a wreaked or abandoned SLC project for some time, as doing this would be a one way street, and I would hate to prototype on a good chassis. The more I play with the ideas, I keep thinking RCR might have a better chassis to use on than the SLC. The ultima has much more room for side pods, and I suspect the 962 and maybe the gt40 might also.

Bob
 

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The GTR is wider.

That does not look like the large Tesla rear unit to me as those have motor each side of the gearbox.

I’d be happy wit RWD as those units pump out well over 600hp and that’s a lot of KW to pump from batteries.

I’d also be ok having a removable pack for passenger side.
 
620hp = 462kw * 90% (efficiency) = 513kw

45 min runtime at WOT * 513kw = 385kWh

Tesla pack weight 14lbs/kWH

385 + 20% (spare capacity) * 14 = 6,468lbs of batteries.

If you recharge at the turnaround you need half that, so 3,234lbs of batteries.

That’s rough.
 

Bob Winn

Supporter
Yeah the Tesla drive is actually a motor on one side of the gear box and inverter on the other. I have removed the inverters for clearance, and moved them in front of the rear wheels.
 

Bob Winn

Supporter
620hp = 462kw * 90% (efficiency) = 513kw

45 min runtime at WOT * 513kw = 385kWh

Tesla pack weight 14lbs/kWH

385 + 20% (spare capacity) * 14 = 6,468lbs of batteries.
w
If you recharge at the turnaround you need half that, so 3,234lbs of batteries.

That’s rough.

So I do not think you are going to need to go WOT for 45 min to see 200 MPH, my calcs using a conservative 4900 pound car, 0.39 CD and 18 sqft drag area, get me the ~400 hp for 200 MPH. Keep in mind I have no experience going these speeds, so I am working for text books. Down force really comes into play, but even if the car is generating 1500 pounds of down force, i only get to 427 HP.

See the attached test power curve. The bottom scale is in MPH, but with the gearing or 9.73:1 and the wheel diameter of 28.3 inches, 75 mph is about 8600 RPM on the motor, about 50% throttle, (16000 RPM max), it is also where the motor is most efficient. The trick is for you to gear the car so that 200 MPH is near this point, but still be able to get off the line. It actually a interesting problem. I guess what I am getting at is I think if you could get the gearing right, the math might be more like

427 HP =318.9 Kw / 0.93 rear drive efficiency = 342.1 Kh

if you have to do 45 min that gives 256 KwH, probably not doable. But really for such a run, I would have some regen turned on, and you could get away with maybe 30 of run time, that gives 171 KwH. Still high, but not crazy. 171 KWh would be about a 700 kg (1500 pound) pack of the new model 3 batteries, (247 WH/kg). I mean its extreme, but its in the realm of possible. The car could probably do much more than 200, probably like 230 MPH, but you would be killing the range, it would be a balance of how well you could hold the car at that average speed. That pack would take 9 hours to charge at 220 volt. I dont think would could make it swapable at that size, but maybe you could. IT would be about 2 of the model 3 packs, I really don't know how one could fit them in a SLC, it would have to be a custom chassis.

Again the issue is the gearing. you would need gear the damm thing way down to like 4-3.5:1 maybe to move the peak performance to your desired speed range. I don;t know if you could get the thing moving from a stand still geared like that, it would be like trying to move ICE SLC from a start in 4 or 5th gear. I think you would need to do a AWD setup with the rear geared low, and the front back at 8:1 or so.

I have only ever thought about doing full speed up and down runs, not time at max. It a really interesting problem.

Good to see some serious EV talk starting up around here.

Bob
 

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Chris Kouba

Supporter
...I keep thinking RCR might have a better chassis to use on than the SLC. The ultima has much more room for side pods, and I suspect the 962 and maybe the gt40 might also...
If you're looking for space, keep moving past the GT40. It barely fits in what it was designed for never mind an alternate technology. They are small. The 962 is notoriously large though, and that may prove an interesting direction. It's intercoolers and radiators were in its side pods back in the day and there would be a bit of room under the body there for you.

...Down force really comes into play, but even if the car is generating 1500 pounds of down force, i only get to 427 HP...
I may be mis-understanding things or not properly doing the math, but I think downforce is irrelevant. I believe the figure you seek is the total force of the vehicle's drag. Thinking of it in a different way, vehicles can generate differing quantities of downforce with differing efficiencies, but I believe the math quantifies this through the Cd. If you increase the downforce, typically the Cd increases, but not all Cd increases raise downforce.

Disclaimer: It's been a really long while since I took any physics.
 

Bob Winn

Supporter
If you're looking for space, keep moving past the GT40. It barely fits in what it was designed for never mind an alternate technology. They are small. The 962 is notoriously large though, and that may prove an interesting direction. It's intercoolers and radiators were in its side pods back in the day and there would be a bit of room under the body there for you.



I may be mis-understanding things or not properly doing the math, but I think downforce is irrelevant. I believe the figure you seek is the total force of the vehicle's drag. Thinking of it in a different way, vehicles can generate differing quantities of downforce with differing efficiencies, but I believe the math quantifies this through the Cd. If you increase the downforce, typically the Cd increases, but not all Cd increases raise downforce.

Disclaimer: It's been a really long while since I took any physics.
I have looked at the few photos of the 962 on Fran's site and I thought the same thing, just plenty of room there to work with. Plus it just looks amazing. But really no room up front for what i can tell for a front drive. It would be a RWD only, but I could be wrong. Also, getting it road legal would be a trip. That is the real nice thing about EV setups, is you can really just press a button, limit the power to the drives, and have a real tame street-able setup. I may start another thread with all the EV talk. I have alot more drawings and concepts.

Bob
 
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