Very loose rear end (Handling)

[Tcoat]

Originally Posted by navanodd

We had a Lego Torsen at my school, really helped to understand how it worked.

But Ubersuber already established that unless it is exactly a Torsen brand it is different! So it must be a Legosen diff that you had.

[Gforce]

Originally Posted by ZDan

I might have to get that Lego one. I have a running argument with my local bartender who insists that an open differential is "1-wheel drive". He doesn't believe that it actually provides equal torque to both rear wheels, I can't convince him!

Switch off the brake actuated "limited slip" traction control on some audi quattro models and you get the same "one wheel drive" effect (really awful in reverse gear) even through the Quattro Torsen transfer case!

[Gforce]

Originally Posted by navanodd

We had a Lego Torsen at my school, really helped to understand how it worked.

Was that an official lego product or did some clever teacher build one? If I could find one I'd buy it. Just for fun.

Or was the teacher's name just Mr Lego Torsen, that famous Norwegian family name?

[navanodd]

Originally Posted by Tcoat

But Ubersuber already established that unless it is exactly a Torsen brand it is different! So it must be a Legosen diff that you had.

I'm so sorry! I was distracted by the neat little gears to realized that the Lego Group did not license the technology from JTEKT Torsen North America Inc.

On the plus side, the plastic gear compound was likely self lubricating for life. What a maintenance marvel!

[Tcoat]

Originally Posted by navanodd

I'm so sorry! I was distracted by the neat little gears to realized that the Lego Group did not license the technology from JTEKT Torsen North America Inc.

On the plus side, the plastic gear compound was likely self lubricating for life. What a maintenance marvel!

But what happens if you put different Lego wheels on each side?

[navanodd]

Originally Posted by Tcoat

But what happens if you put different Lego wheels on each side?

You end up with zero excess differential heat when racing your Lego car on an oval track. Obviously the inside wheel must be the smaller one.

[Tcoat]

Originally Posted by navanodd

You end up with zero excess differential heat when racing your Lego car on an oval track. Obviously the inside wheel must be the smaller one.

[Gforce]

This is pretty interesting. Japanese corporate brochure but with English.

http://eb-cat.ds-navi.co.jp/enu/jtek...catd1001je.pdf

Apparently the friction involved in torque biasing of helical differentials is axial against the bore.

And this seems pretty straightforward:

https://members.rennlist.com/951_rac...84gleason.html

The worm wheel (side gear) can drive the worm gear (spider gear) but not the other way around. The carrier transfers pinion/crown gear torque equally to the worm gears and then to each of the left and right side gears. Any difference in torque reaction results in the worm gears locking together and requiring the side gears to turn at the same rpm dividing the torque proportionally to the resistance of the tire and driving the side gears at exactly the same rpm instantaneously. However, rotational forces coming the other way, from tire to differential, cause the worm wheel (side gear) to drive the worm wheel which provides constant differentiation capability regardless of torque applied at the pinion and regardless of the direction of that torque at the pinion.

Helical versions work on the same principle but the worm gears are in parallel to the worm wheels instead of at right angles, saving one set of spur gears per set of worm gears. Torque biasing capacity is higher in the T1 right angle setup.

So, Torsen diffs "lock up" immediately under torque applied between the pinion and the tire, either direction, but simultaneously remain unlocked as between each wheel. This simultaneous locked but unlocked condition is the advantage and disadvantage of the Torsen at the same time. The locking is instantaneous, under torque delivered by or to the pinion gear no differentiation is possible, however as between the two drive wheels differentiation is always possible regardless of the amount of torque applied at the pinion and regardless of whether the torque is directed from or to the pinion gear.

Under braking the Torsen is completely open. Under power or lift off the Torsen is completely locked except that as between the drive wheels it is completely open. You cannot help noting that wheel speed differences cannot cause any wear in the differential. The diff differentiates freely without any changes caused by any applied torque. No wear results from the amount of torque and normal minimal wear results from any differentiation, just as for an open diff. The torque load has no effect whatsoever on the differentiation. Brilliant and elegant engineering.

Under very hard acceleration on dry road you can feel the differentiating as the grip is alternately transferred left to right and back again. On slippery surfaces where both wheels have limited grip, wet or snow or ice, this left to right and back again squirming is very noticeable. On a drag strip this could become dangerous. On a race track not so much.

On a dry road and in a straight line you get perfect 11's every time, confirming the instant lock up capability of the Torsen.

[Gforce]

Originally Posted by navanodd

You end up with zero excess differential heat when racing your Lego car on an oval track. Obviously the inside wheel must be the smaller one.

Has to be. Plastic is not very heat resistant. No lube either.

[navanodd]

Originally Posted by Gforce

This is pretty interesting. Japanese corporate brochure but with English.

http://eb-cat.ds-navi.co.jp/enu/jtek...catd1001je.pdf

Apparently the friction involved in torque biasing of helical differentials is axial against the bore.

Makes sense, helical cut gears can generate a lot of axial force.

The primary reason that racing gearboxes use straight cut gears is so that stronger, heavy transmission casings are not required to hold the axial load.

[Gforce]

Originally Posted by navanodd

Makes sense, helical cut gears can generate a lot of axial force.

The primary reason that racing gearboxes use straight cut gears is so that stronger, heavy transmission casings are not required to hold the axial load.

Not only that, the really clever bit is that if the worm wheel drives the worm gear it does so in the opposite direction to the applied torque. When that happens the worm gear is generating axial force opposing the axial force that the driving torque applies. The worm gear then moves away from the case allowing it to rotate. When one wheel differentiates in speed it reduces the torque bias force at the worm gear thus allowing the differentiation.

That's why you get no unusual gear wear in a Torsen. When it differentiates it unloads the gears that would otherwise bias the torque. At least, that's how it appears to me now that I think it through to the end. I'm not an engineer.

[ZDan]

Originally Posted by Tcoat

He should have been with me when the diff on my 64 Impala locked up on me at 70MPH.

Dude, you have (or had) a '64 Impala SS?! Mad props...

[humfrz]

Originally Posted by ZDan

Dude, you have (or had) a '64 Impala SS?! Mad props...

Ya, ol @Tcoat goes waaaaay back.

I'm guessing he had that custom "weathered" paint job. Yep, betcha it was cherry ..... cepten for the missing hubcap .......


humfrz

[chaoskaze]

Originally Posted by Gforce

On slippery surfaces where both wheels have limited grip, wet or snow or ice, this left to right and back again squirming is very noticeable.

so that's why my car was doing that on snowy uphill on stock tire....hmmmmm

thumbs up to you my sir, now i understand how my car behaves even more.