Very basic trike question...

[Beast-of-Burden]

I built a VW trike back during High School (1970) but have been on 2-wheels since.
My question is the rear drive wheel. I see some (motorcycle based) trikes that used converted auto differential (like a Jag) which could be a 'limited-slip' type. I see some kits that look like only one of the two rear wheels gets powered. I'm not asking how many prefer a limited-slip set-up over a single wheel drive set-up... Just how much advantage is there in a trike set-up to have limited slip? Converting a chain-drive motorcycle into a trike where the left rear wheel is the drive wheel would be an easier & lighter drive conversion (DIY... not a kit) plus the right wheel could be available to adapt an electric reverse set-up to (with electric clutch & neutral switch controled power source).

 

[flyer91]

IMO, a conventional limited slip has an advantage over a single drive wheel when the limited slip is seeing the same, or close to the same taction to both wheels.
This is because a conventional limited slip transfers most torque to the wheel with the least traction.
A torque sensing limited slip differential does the opposite (more below).

So ..... if using a conventional limited slip differential in a situation where the right wheel is in mud and the left is on pavement, the traction is not going to be as good (in this same scenario) as a single driven wheel system that has it's drive wheel on the left, and vice versa for an opposite scenario.

But also because you still get 'some' torque to the wheel that has the most traction with a conventional limited slip diff, it (in practical use) has an advantage over a single drive wheel because in most situations it will provide some traction to the wheel with the most traction where a single wheel will leave you pushing if the drive wheel is in the muck.

As indicated ....... the best limited slip drive system is a torque sensing system because it is constantly applying the most torque to the wheel with the most traction, in a way that proportionaly matches that traction at any time.

Biu I don't know of any trike kit using a torque sensing diff.
They are heavier, more complicated and more expensive than a conventional diff, and really not needed on a trike.

 

[Loner]

I would compare your need for limited slip differentials to your day to day use of your own vehicle. How often do you find yourself in a problem due to lack of traction? Yet chances are that your daily driver is not limited slip. Conventional differential should make 99.9% of our rider friends happy on a trike.

However, you need to open your mind a bit about how the drive would be transferred to the rear wheels from the chain/belt. If you take a conventional automobile differential ('chunk'), toss the ring gear and replace it with a sprocket, the drive transfer would still be to both sides so long as one does not just totally lose traction. So it would not drive to the 'left side only' as you describe.

You could still add a reverse in there somewhere, but not to a dedicated drive axle.

For homebuilt applications, my opinion is that you would be best to find a driveshaft type motorcycle for the conversion and adapt the shaft to a suitably small vehicle rear end. If the rotations don't happen to agree, just flip the rear end upside down and that will reverse its input.

The inclusions of posi-traction differentials, independent rear sspensions, etc. are great icing on the cake, but usually apply to the 1% of our most meticulous builders and are not necessities for great trike conversions.

Wow, just talking about this makes me want to go junk yard digging to look for a rear end to drop behind my BMW I just finished. I'd just need to adapt that gizmo to fit that thingamabob and make that whatchmacallit line up with that widget. Shouldn't cost me much more than a few bucks . . . . Later, guys!

 

[Dwight]

Using a limited slip differential on a trike is certainly do-able. The real problem is going to show up when you try to steer your trike. Limited slip vehicles, at least most of them, want to go straight. If you have power to both wheels your ability to steer with only one wheel becomes limited, more so with less weight. I hate it when people bring up the old 3 wheel atv's with the solid axle in discussions about our trikes, but in this case it is usefull to illustrate what happens. These had to be steered with body english and throttle or driven very slowly. I still use body english and throttle on my trike (not when the missus is riding passenger!) when I get in a sporting mode.
If you do use a differential with a ring and pinion and need to flip it for the right direction you need to make some provision to lube the pinion bearing. On most differentials it is splash lubed with a large opening on top and a very small one on the bottom. When you turn it upside down you won't get enough lube.

Dwight

 

[Beast-of-Burden]

Thanks for your reply...
Back in my little work shop I've got the complete rear sub-frame that was in a BMW 528. It's independent suspension with a limited slip dif. I understand the advantage of limited slip when one wheel isn't getting traction in a car but I question the advantage on a light (single wheel steering) trike set-up. If both rear wheels are getting traction on good pavement I would think it would make it harder for the front wheel to steer properly while fighting the limited slip action on the rears. Modifing a shaft-drive bike to power the car rear end is the 'norm' but if it's a chain drive bike I would think the 'limited slip' diff would still work. There's a spacer between the axle shafts & the diff that could be replaced with a rear chain sprocket. The limited-slip unit would still 'sense' the axle turning as if it was the pinion gear doing the turning or not. (no drive-shaft attached)
If there isn't as much of an advantage of limited-slip on a trike as there is in a car... then a lot of weight can be trimmed (with modifications).

 

[Beast-of-Burden]

I built this when I was a teenager...
http://www.flickr.com/photos/beast-of-burden/4681412668/in/photostream
This is the BMW rear end idea I was thinking of doing a trike with...
http://www.flickr.com/photos/beast-of-burden/6113742837/in/photostream

 

[flyer91]

I'm not sure that the limited slip would cause it to be 'noticeably' harder to steer when both wheels see the same traction.
The steering would be neutral 'only' at that time.
But 'if' it does impact the steering to a point that you would notice it, it should be when the wheels don't have the same traction.
And because either a conventional LS or a torque sensing LS diffs are constantly (but inversely) changing the torque to each wheel based on traction, that might 'theoretically' impact the steering.
But I suspect that even 'that' is a moot point, because ....... even with a single driven wheel your trike doesn't snap right (assuming a left driven wheel) when you blip the throttle, or left ....if it's a right driven wheel, to a point that is noticeable in any practical and comparative sense (to the 'same-traction-scenario' with a LS diff), and/or do the opposite when you chop the throttle and/or downshift.