Redesigned T-20, T20-M

[shawngray66]

Hello Folks,

I have completed the preliminary design for a new T-20 tranny that is more robust, easier for the layman machinist to manufacture and should be downright bulletproof. I have completed all the tolerance checking and it is not ready to move to drawings and prototyping.

A few key improvements are shifting with dogs vs gears (same as in motorcycle transmissions), more robust gearing, and internal bearings vs inserts.

If there is anybody out there interested in helping get this design off the ground let me know. My UTV is ready and this design was done out of necessity as there were no other good options.

UTVs.jpgT20-M Transparent.jpgT20-M Cutaway.jpg

[oldstreetracer]

I noticed in the last picture that the drive clutch is extended out from the engine. I am sure that due to leverage and vectoring forces the engine bearings or crankshaft would suffer premature failure. I like the T20 improvements.

[shawngray66]

Yep. The engine and drives are for representation only. That shaft would need to be supporting by a bearing certainly. Since the acquisition of Recreatives and the subsequent business problems of selling tyranny's to competitors, and IP out their for LATV track hydraulic systems it was done out of necessity. This transmission is a much improved version of the old. Thanks for the feedback.

[dirtdobber]

It would be handy to incorporate a removable sprocket on the output shafts. Currently on the t20, you have to do a complete teardown to replace a sprocket. Surely there is a better way.

[shawngray66]

Agreed. I plan to use a keyed or splined sprocket.

[shawngray66]

Improved Break Actuation and Linkage

Break Linkage.jpg

[wfo]

I think the only way to get this off the ground would be to make it fit all the older machines. it would have to be cheaper and better
if not a newer T-20 would still be king

[whipper-ag]

I think the only way to get this off the ground would be to make it fit all the older machines. it would have to be cheaper and better
if not a newer T-20 would still be king

I agree, It must fit the older machines.
How is the braking improved?
A cad drawing is just a picture.
Things always look great on a computer.
It's gonna take some real life testing to prove it's bullet proof.
WFO and I would love to do the testing on it when your done.
You may be on to something.

Whipper

[shawngray66]

Gents,

Good points. This design utilizes gear dogs for engagement and is heavier in design. It takes after drag bike engines and trannys that are extremely tough. I am currently designing a new ATV and this was done for necessity for my machines to accommodate heavier machine weight, more HP, and manufacturing simplicity. I do understand drop in and lower cost are important if that is the segment I was pursuing.

I have attached an image showing the beginnings of the skid that will carry this.

To the braking question, the actuation of the brakes is improved by using a better more adjustable linkage system. As for the internals, a band stops the rotation of the hub as in the older with the exception of using one bigger band vs a small one that makes several wraps.

I will be glad to send out much larger pictures to get a better idea of the internals. These pics come from a fully toleranced model that will be ready to go into testing soon.

[msafi65]

The brake bands in the T20 act very much like a capstain winch in principal. The friction tightens the band grip on the drum. I've attempted to build a rear lever t 20 for a guys track vehicle and in doing so the bands didn't tighten with friction. It took extreme force on the sticks to drive it. At the time I didn't realize how much grip the bands gain with friction tightening them. I like the dog system for engaging forward and reverse. I've also suggested to RI and others that the ring gear drum could be fabed in three pieces much like newer automatic transmission drums.

[jerseybigfoot]

You may want to reconsider your band design and copy the spiral design as it is self energizing with low input force to high friction force. The redesign will be more like an on off switch for the self energized rotation and hard to engage in the other direction

[shawngray66]

msa

You bet. Make everything simple to fab using run of the mill machines. As far the bands, I have spoken to a company that applies the very high end brake pad materials to race pads. Cant use ceramic where there are bearings but this stuff is supposed to be good. I have about 270 degrees of wrap with very wide bands. They will cinch when drawn. if it is not enough for use with 40 HP then I have another plan that is a bit more expensive that uses hydraulic systems like motorcycles. Good point though.

[JoeMeg]

You may want to reconsider your band design and copy the spiral design as it is self energizing with low input force to high friction force. The redesign will be more like an on off switch for the self energized rotation and hard to engage in the other direction

My sentiments on this topic,precisely. Just offerin' my two cents.