More little tractor tranny ideas needed

[Beck]

I knew my little project was moving along slowly but not until I looked back at my posts here about it did I realize how slowly. I posted some photos back in July. It doesn't look much different.

http://www.roddingroundtable.com/forums/viewtopic.php?t=13665

I was looking for my post about a lightweight transmission for this project and found it back in Dec 2014.

http://www.roddingroundtable.com/forums/viewtopic.php?t=13521

I would like to revisit that transmission question.  Back then I decided to use a 350 turbo transmission. The tractor is now roughed together. I took it to the local scale. It and I are overweight. Before I posted the weight with driver had to be under 1400#. The rules changed a little. The maximum weight is now 1350#.

I have found another transmission option. There are 2 places making Saginaw 3 speed (M15) housings in aluminum for the circle track guys.

http://www.mitchell-machine.com/bullet.html

http://www.magnusracingproducts.com/saginaw/

Each is willing to build a transmission with 1st and reverse gear only and to eliminate the tail shaft. Everything not needed internally will be removed. The expected weight of the transmission is 45 to 50# without the bell housing. My 8" converter weighs 25#. The clutch I'm looking at is 15#. (Ram is designing a new clutch for tuner cars that require some slip for turbo spooling.)  After adding a throw out bearing, pedal, etc. it would still be a 60 to 70# weight savings. I have my option of the 4 available low gear ratios. Everything custom comes with a price and this isn't cheap... The tranny and clutch will be over $3000.

Doug Nash built quick change transmissions in the 80's for dirt track cars, but I have not been able to locate one.  One guy I pull against runs them.

I had another post way back asking to ID another modified manual transmission. It wound up being a GM 3 speed case from the mid to late 50's with tail shaft removed. It was iron and still pretty heavy. That tractor runs a Crowerglide.  If I went with this style clutch it would be an additional $1400 over the Ram, but wouldn't need a pedal or throw out bearing.

One unsolved problem with the Saginaw tranny is what to put on the end of the transmission output shaft. The splined end will be cut off. The section of shaft in front of the splines is a smaller diameter so it can't be resplined. Do I have the guts to cut and weld it? As of now I have welded axles in the rear axle, but I'm thinking I want to buy good ones. I could put one or multiple keyways into it. One shop said weld a coupler on the shaft until I ask about how to disassemble it since that shaft is installed into the tail shaft housing after loaded with the gearing.

What do you guys think?      It may be time to just throw in the towel and admit the motor was too big and I'm too fat.

[enjenjo]

What is the diameter of the smaller part of the shaft?

[Beck]

What is the diameter of the smaller part of the shaft?

I'm sorry but I don't have that information.  
From photos of the part I can see that it is smaller. That was confirmed by one of the shops.  
All of those original transmissions around me are long gone, either to the crusher or to the circle track guys. So many were removed from restored cars and replaced with more desirable transmissions.
All my old junkyards have closed and have been replaced with the U-Pick-A-Part type places. They don't bring anything that old in. I have put some feelers out but that's like fishing. Sometimes you don't get a bite.

[Beck]

One shop suggested I not use a transmission. They recommended just running a clutch and fabricating a bearing plate behind it. The suggestion was to marry an input and output shaft with a bearing or two in the middle. The rest of the drive line would be sprockets and chains.  One pair at the clutch and another at the pinion. The motorcycle powered tractors in the class use chain and sprockets successfully, but they have less torque.
 
2 issues I have with this is there is no neutral and no reverse. The clutch would need to have a catch or locking mechanism to hold it disengaged. If a hydraulic throw out bearing was used a line lock would work. My fear is a small hydraulic leak could slowly allow the clutch to engage. If a hand clutch was used (don't like that) there could be a detent installed like on a mower deck to lock the deck in the top notch. I don't know how well that would work on a foot pedal.  

Another thought on a hydraulic throw out bearing is putting a small port in a pressure bleed off line to get consistent clutch slippage at disengagement. Don't nitrous lines have ports in them? This could just be another tuning problem. Sometimes manual operation is the easiest.

[enjenjo]

The reason I asked, there are other yokes available that are smaller diameter. You could have the smaller part of the shaft cut for the smaller spline. One in particular is a Mopar 6 cylinder spline that is 26 splines with a OD of about 1 1/8 on the shaft.

[Beck]

Here is info I found on the GM.
Transmission Slip Yoke •27 Spline x 1.176" Diameter
•Seal Diameter 1.502"
•Fits GM TH350, 700R4, 4L60E Transmissions

Here is the Mopar
Transmission Slip Yoke •26 Spline x 1.158" Diameter
•Seal Diameter 1.558"
•Fits Mopar A-904 Transmissions

That is unless there is another small Mopar spline?
I wonder if there is something smaller in the imports?

[kb426]

If you can change rear end ratios, how about a used lenco reverser? I believe it's possible to create a detent for a neutral. The chain drive deal sounds like a severe power user.

[Beck]

There is a really nice lightweight reverser here.
http://www.roadstercycle.com/Reverse%20gearbox%20for%20motorcycles.htm
The pictured tractor is using the reverser.

I don't know what a used Lenco reverser costs or how big it is. There was one motorcycle powered puller using this last weekend. He likes it. I doubt this one has a neutral position.

The motorcycle powered pullers are pretty much committed to at least one chain connection. Those mounting the motor like installed into the bike normally use a jackshaft so they run 2 chain reductions. Those who put the motor inline need 1 chain connection because their transmission is so far offset. Some drive an automotive transmission others do a gear reduction drop direct to the driveshaft. That is what the pictured tractor is using.

Judging by finishing positions, the inline motorcycles seem to have a slight advantage. That indicates that the double chain drive is using more power.

[kb426]

The reason I mentioned the Lenco unit is because they have been manufacturing them for decades. They were designed for 1500 hp. and above. The shafts on them would need to be adapted to your clutch shaft size. The old ones for high gear only might be doable but most of the dragster cans are either 7.5" or 8.125" deep. Without being able to machine the shaft to fit, this would be a bad idea. I wish I had a better idea.

[Beck]

In a previous motorcycle powered tractor I built a planetary reduction into the rear axle. I ran 1 chain from the motor to the planetary input. Something gave this tractor an advantage, because it was winning. I expect the planetary was more efficient than their 2nd chain reduction. I sold it about 10 years ago.
My machining left something to be desired. The planetary started as an overdrive from an automatic car tranny. I had to do some welding during construction. Every time I would weld on it things would shrink, making the tolerances too tight. The gearing was so hard that I had a terrible time machining it. I cussed it many times during the build. It always leaked fluid.

The planetary portion is on the left. It was missing an oil seal on the right axle shaft here yet. Since there was no differential it only used 1 brake which was installed on the right to offset the planetary weight. The outer axle tubes and axles were 8" Ford.

[Beck]

This is a photo of the above tractor with the planetary rear axle. It was powered by a Suzuki GSXR 750.

That is a lower powered class than the one I am currently working on.

[Beck]

Another photo of the old one.

The current project will not get any sheet metal. I just can't afford the extra weight. The motor will hang out in the open. Fenders are required, and I will need something to put a few gauges on. That will be it.

[enjenjo]

If you look here  http://www2.dana.com/pdf/J300-P3.pdf  You will find a variety of yokes in different sizes. Moser can cut new splines, and the price is reasonable. The last one I had done they did while I waited, and cost me $75.

[Beck]

I wonder if Moser has the tooling  to broach internal splines?

I'm still considering not using a transmission and using chain reduction on a jack shaft. I am looking at this type of sprocket.
https://www.motionindustries.com/productDetail.jsp?sku=00177585
If the output from the clutch shaft and the sprocket hub were splined it would make gear changes pretty quick. The shaft would need some type of retention method to hold the sprocket. I could have several size sprockets for gear changes.

For the bearing on the clutch output shaft I was considering a wheel bearing from a FWD car. I was hoping that would allow just using one bearing to support the shaft. The bearing would be located at the back of the bell housing with the sprocket rearward of it. The shaft would be unsupported past the sprocket. This is a Honda piece. There are others available with larger bores.
http://www.oreillyauto.com/site/c/detail/BCA0/510015/03336.oap?year=1997&make=Honda&model=Civic&vi=1168938&ck=Search_wheel+bearings+%26+seals_1168938_1335&keyword=wheel+bearings+%26+seals
The bearing could be pressed into a tube that was welded to a plate bolted to the bellhousing. The length dimensions would need to be worked out to locate the shaft into the crankshaft pilot bearing. Obviously everything would need to be turned to center into the bell housing bore.

The clutch/output shaft is a problem. I was looking at photos of transmission input shafts. After the input bearing they are all pretty short with a gear attached. That gear is counter bored so it couldn't be machined off creating more shaft.  My thought is a hybrid shaft made from welding a manual transmission input shaft to an output shaft. There would probably need to be a sleeve pressed onto the middle of the shaft to accommodate the bore of the wheel bearing. If the sleeve was placed over the weld joint it could be welded to help strengthen that joint. The shaft length would be kept to a minimum to reduce the leverage of the chain tension.

[54stude]

Any progress on the tractor?