Electric ATV conversion. Integrated transmission removed. Need jackshaft reduction and diff split. Looking for design help.

[bneely]

My 13 year old son is trying to convert a utility ATV to electric for real off-road/ranch use, not a toy. I am a lot over my head here in trying to help him so any help would be greatly appreciated.

The original ICE and integrated transmission are fully removed. What remains are the front and rear differential input shafts (splined). There is no gearbox, no reduction, no reverse.

I’m looking for help designing a mechanically sound drivetrain, sspecifically:

• Motor selection (single motor preferred)
• Total reduction ratio targeting usable low-speed torque
• Jackshaft layout with proper bearing support
• Chain or belt reduction stages
• Mechanical split to front and rear diff inputs
• Practical considerations for durability

This is not a hub motor project and not an e-bike or gokart build. The quad needs to pull, crawl, and survive abuse. Does not need to be geared to be super fast, top speed of 35-40mph would be just fine.

We live off grid and I have built and maintained several solar battery systems over the years. My latest is a Victron 48v lithium battery system. So the electronics don't worry me as much as figuring out the mechanical drivetrain.

Assumptions so far:

• 72V or 96V system
• Industrial EV motor, not hobby grade
• Two-stage reduction likely required
• Electronic reverse via controller is acceptable

What I’m looking for is design guidance, calculations, and layout sanity-checking from someone who has actually built or designed drivetrains. If there was a DIY drivetrain kit that I could purchase that would be fantastic. I do have friends that are machinist but I don't have those skills or tools. Welding and minor fabrication is no big deal.

If you’ve done:

• Electric ATVs / UTVs
• Electric karts with real reduction
• Baja SAE electric
• Industrial chain or belt power transmission

I’d love to hear from you. Happy to compensate for serious help.

Thanks.

 

[A-DamW]

The original ICE and integrated transmission are fully removed. What remains are the front and rear differential input shafts (splined). There is no gearbox, no reduction, no reverse.

Do you still have the transmission?
What kind of transmission was it? CVT belt drive? shift-able multi gear?

I have a Yamaha Grizzly quad I am going to convert to EV, I am going to reuse as much of the existing drive train as possible.

Electric karts with real reduction

I built a go-kart with my pre teen son, it goes about 5MPH(for safety), it can lug my 180lb's up the 16%(measured) grade behind the house using ~500 watts.

What is the gear ratio on those differentials? judging by the size of the punkins, maybe 2~4:1?
that may be enough to do a deep single stage reduction, the differentials being the second stage.

What I’m looking for is design guidance, calculations, and layout sanity-checking from someone who has actually built or designed drivetrains. If there was a DIY drivetrain kit that I could purchase that would be fantastic. I do have friends that are machinist but I don't have those skills or tools. Welding and minor fabrication is no big deal.

I'm not going to claim to be a professional, but I have designed and built a lot of mechanical and electrical things.

We live off grid and I have built and maintained several solar battery systems over the years. My latest is a Victron 48v lithium battery system. So the electronics don't worry me as much as figuring out the mechanical drivetrain.

I have lived off grid, off and on over the years.
For some reason, I was always the one who ended up managing and maintaining the solar/battery system(if it was not my system)

Let's get this convo going! looks like a fun project.

 

[A-DamW]

I’m looking for help designing a mechanically sound drivetrain, sspecifically:

• Motor selection (single motor preferred)
• Total reduction ratio targeting usable low-speed torque
• Jackshaft layout with proper bearing support
• Chain or belt reduction stages
• Mechanical split to front and rear diff inputs
• Practical considerations for durability

When I get a moment, I'll try to answer these questions in more detail.

 

[Papa]

...usable low-speed torque - ....top speed of 35-40mph

Without, at least, a 2-speed (more likely 3 or 4 speed) operator shift-able transmission, a low speed 'crawler' with enough grunt to pull implements, ect, ... and is expected to reach 35-40 mph,.. is a bit of a stretch.

What remains are the front and rear differential input shafts

This is easy.... a third differential feeding the front and rear differentials via the third's axles. This arrangement would also give you a double reduction. But again, a single-speed 'stump puller' is unlikely to achieve the 30+ mph without a tranny.

 

[Papa]

Thinking...
Some 7 or 8 years ago, I did a frame-up John Deere garden tractor build. Powered by a Kawasaki 18HP liquid cooled V-twin, and coupled to a Peerless 820 6spd transaxle (still using it today). Might be a possibility to use a similar transaxle if it'll squeeze between the front and rear differentials of your beast. That'll not only combine a third, center mounted differential (as mentioned above), but also includes an integrated multi-speed transmission in a compact package. Peerless also has manual, hydrostatic, and electric transaxles (primarily for garden tractors and rider mowers). I can take measurements of my 820 between the wheels.

The 820 i'm using is manual, but incredibly smooth shifting (often clutchless) - specs show 450 ft/lbs of torque output. 1" OD axles and V-belt driven. However, because of the double reduction, you'll not see anything close to 30 MPH.

Products | Peerless Gear

 

[scianiac]

Without, at least, a 2-speed (more likely 3 or 4 speed) operator shift-able transmission, a low speed 'crawler' with enough grunt to pull implements, ect, ... and is expected to reach 35-40 mph,.. is a bit of a stretch.

I don't think that's necessarily true, IPM motors can really extend the operating range and with a large enough motor and high enough current you can have all the torque you want, those taking the space and weight the gearbox would take up. Now there are limits but the question is how much torque can you really use in an ATV before you lack the traction to apply it? And you will compromise efficiency in one of those conditions. If a gearbox can be found that has multiple gears and the center diff or center locker all in one package that would be great option though. In most EVs multiple gears are a waste but it could work well here.

 

[PaPaSteve]

It's been nearly 20 years since I helped with a ATV / EV conversion project.
The intent was for vineyard usage.
My task was doing the fabrication, welding, machining, battery box etc.
The chassis was a Kawasaki 400 with chain drive to the solid rear axle.
Primary parts used : 48V golf cart motor, Curtis controller and CATL lithium batteries.
Finished project had plenty of low end grunt and too much speed.
No reverse was installed but could have been done electrically with a reversing contactor.

Our family has owned several NEV's (Neighborhood Electric Vehicles) essentially street-able golf carts.
They were 72V that were governed by regulations to a max of 28 mph.
Reprogrammed they could hit 50 mph which was too fast for the suspension and brakes.
40 mph was a better fit.

To sum up . . .
A single speed is all that is needed.
Look to NEV's or golf carts for parts and inspiration.

Happy Trails to you.