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Discussion Starter · #1 ·
I am in the process of planning my Conversion before I even buy or start anything. It is a 35ft long 1963 GM PD4106 Coach Bus with a very particular rear powertrain set up. It is a v-shape drive axle and the motor actually runs in the opposite direction of 99.9% of other motors. (8v71 Detroit diesel) it has a 4 speed manual double clutch and I want to just bypass the transmission and go direct drive. The current motor max rpm is 2100 and I found a motor strong enough that runs at 1800rpm max. Rear axle ratio is 4.125:1.
If I just run a constant .7:1 gear between the motor and the axle diff would I be able to effectively take out the 4speed bus transmission?
 

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Discussion Starter · #3 ·
If the proposed motor can run at only 1800 RPM, it is almost certainly unsuitable. What is it?
300hp industrial electric motor. But I think it will just be easier to replace the axle with a newer T drive.. alot more options there.
 

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It is a 35ft long 1963 GM PD4106 Coach Bus with a very particular rear powertrain set up. It is a v-shape drive axle and the motor actually runs in the opposite direction of 99.9% of other motors. (8v71 Detroit diesel)...
Now that's amusing engine trivia: apparently those Detroit Diesel 2-strokes were available in either rotation, but the transverse engine V-drive buses used left hand (clockwise when viewing the flywheel) rotation. The vast majority of engines are right-hand.

Fortunately, this won't be a problem in an electric conversion, as the motor can rotate either direction when set up properly (especially if it is brushless).
 

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300hp industrial electric motor.
So this would likely be an induction motor intended for 60 Hz... and it must be huge.

But I think it will just be easier to replace the axle with a newer T drive.. alot more options there.
That's likely true.

You're still going to have the same situation: a rational motor choice will likely need to run at higher speed than the axle's pinion shaft (so it needs a gearbox between the motor and the axle), although there are some motors intended to be used without additional reduction gearing, such as the TM4 Sumo MD and Sumo HD.

If you have lots of money and can get a single unit out of Dana, you can even get a motor mounted directly on a suitable axle, e.g. eS9000r e-Axle, eS13.0xr e-Axle
 

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Discussion Starter · #6 ·
Now that's amusing engine trivia: apparently those Detroit Diesel 2-strokes were available in either rotation, but the transverse engine V-drive buses used left hand (clockwise when viewing the flywheel) rotation. The vast majority of engines are right-hand.

Fortunately, this won't be a problem in an electric conversion, as the motor can rotate either direction when set up properly (especially if it is brushless).
Yes but is the axle ratio an issue? Would I want a motor with more rpm than the 8v71? (2100 rpm max) I wouldn't want to put unnecessary stress on the 58 year old axle diff. (4.125:1)
 

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Yes but is the axle ratio an issue? Would I want a motor with more rpm than the 8v71? (2100 rpm max)
Yes, as I said, a rational motor choice will likely run faster, and so its output will need to go through a reduction gearbox, because there isn't enough reduction in the stock axle (or any available conventional axle).

I wouldn't want to put unnecessary stress on the 58 year old axle diff. (4.125:1)
Your motor choice won't change what happens to the axle or the differential and final drive gearing in it. Whether, at a given highway speed, the motor turns 2000 RPM and drives the axle directly, or 8000 RPM and drives the axle through 4:1 gearing, the speed and torque on the shaft to the axle is the same.

The main reason to change from the V-drive to a conventional ("T") drive is simply for availability of axle parts as a maintainability issue. You could mount the motor off in the corner to line up with the V-drive shaft if you want, although space for a higher-speed motor and a gearbox may be an issue.
 

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Discussion Starter · #8 ·
Yes, as I said, a rational motor choice will likely run faster, and so its output will need to go through a reduction gearbox, because there isn't enough reduction in the stock axle (or any available conventional axle).


Your motor choice won't change what happens to the axle or the differential and final drive gearing in it. Whether, at a given highway speed, the motor turns 2000 RPM and drives the axle directly, or 8000 RPM and drives the axle through 4:1 gearing, the speed and torque on the shaft to the axle is the same.

The main reason to change from the V-drive to a conventional ("T") drive is simply for availability of axle parts as a maintainability issue. You could mount the motor off in the corner to line up with the V-drive shaft if you want, although space for a higher-speed motor and a gearbox may be an issue.
You make a good point with the propeller shaft torque.. I could get a shorter shaft and get a right angle reducer gearbox to direct the motor more toward the middle.
 
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