Stretching driveshaft *guaging interest*

Stretching the shaft is not hard to do... If someone sends me a shaft and housing/swingarm Ill gladly stretch it for free (just pay shipping both ways....)

Once I do one for a proof of concept Ill offer the service for a real reasonable fee. I estimate $150-200.00 for each shaft. I will know exact fee after I complete the first shaft. My goal is to offer the service as cheap as possible to help out XJ bobber builders, not to get rich.

On another forum I saw someone who paid in excess of $1600/ to have a new shaft machined, thats crazy rediculous.

I used to do hybrid engine swaps on import cars which would require a lengthened or shorten axle to mate a Honda trans to Porsche stub axles for example... Basically you are just putting a sleeve around the axle shaft and plug welding it together.

I would also be able to add caliper mounts for use with XJ900 rear wheels and possibly linkage mono shock conversions depending on the length of swingarm. Virago style monoshock conversions can be done on stock length swingers as well.

If someone sends me the parts Ill demonstrate.


Jay

 

I wish I wasn't in Iraq right now. My shaft would already be boxed up and on its way to you. I should be home for vacation in about 5-6 months. Can I take you up on it then?

 

Where are you. I think I have a shaft and a swingarm in the shop. Iam about to start on my third Maximn refurb and want to do something different with this one. Colorado here.

 

I am in SoCal, zip code 92340.....

Jay

 

I plan on stretching a shaft as well and have a similar background with the Honda/Porshe axles. I used to work for an import race shop on the east coast. We got the best results by cutting the ends of the sleeve on a 45 degree angle instead of square across. I currently don't have access to the tools to do my own so if you still need I would be willing to ship mine out. It's a Maxim 750. Everything is disassembled and ready to go. Let me know dude.

 

Hmm .. we were doing the opposite to Sabre/Magna shafts not long ago. Taking a few inches out of the shaft/swingarm to shorten up those 61+ inch bikes a little.

Funny how things work like that ... longer for some, shorter for others. Small planet.

Do you balance the driveline when you're done? We found that it was pretty much required or noticable vibrations would set in. In our case it actually got easier to balance and less critical since the shafts were shortened, one might imagine that making them longer might make balancing even more necessary and critical as well.

Nice idea, best of luck with it!!

 

One question? You will be balancing it when finished I hope? I have read numerous write ups on how people have lengthened the drive shafts and all of them had to be balanced. Oh, and how long do you think it will take? SO I know when I should have the rest of the bike done.

OK, so its like $22 one way shipping. I am in if you can answer the above questions. When would you like me to ship?

~M

 

can't wait to see how this turns out...

 

Well, we have a doner shaft. Soon it'll be on its way to Jay.

 

FAIL: Motorcycle driveshafts spin at around FOUR TIMES that of car halfshafts. When your bike is in top gear, the driveshaft RPM is equal to that of engine RPM. Car halfshafts spin at rpms reduced 3x to 5x by the final reduction gearing. Bike driveshafts are in place BEFORE the reduction gearing and therefore spin at full engine RPM (when in top gear). Be careful goofing with this stuff, fellas!

I would think that balancing is absolutely required. Car half-shafts spin at wheel RPM, not engine RPM. So balancing car halfshafts isn't as critical, if even necessary at all. But a 10krpm bike drive shaft definitely needs to be balanced.

So I'm not sure how well techniques applied to splicing/shortening car half shafts will work on motorcycle drive shafts. Automotive stub axles spin at wheel rpm, not engine rpm. I dunno man, it's kinda like saying "hey I have a MIG welder and a hacksaw, I'll shorten your cams for you if you send me your parts". Um ... ok.

I'm no expert, just a guy with questions. I'm just trying to figure out if this will actually work. I'm not sure I'd want to be the test-piggy on an untested design idea of this sort (and I'm a pretty pro-experimental kinda guy, too!), especially if the driveline comes apart at speed .... !!!!!!!!!!

We're not talking about just stretching a chaindrive here, folks. I'm terribly sorry for being the negative nelly here ... but this sounds very dangerous to me. Frying a halfshaft on a car at speed is one thing, tossing a driveshaft on a bike at speed is an entirely different thing altogether.

Tell ya what .... how's about you do the first one, post a video of a hard core test ride at WFO throttle, and THEN I'll send you parts and moneycheck. Que no?

Otherwise .. how's your liability insurance payments doing? Hopefully current?

 

I'm leaning towards holeshot on this. Even rear wheel drive shafts on cars have to be balanced. Welding a collar in place to hold the two drive shafts together will definitely lead to an unbalanced component. Even if it's cut dead center the collar will add weight that will lead to a bent shaft. If you do attempt this, at least add a safety ring just in case. :wink:

 

To holeshot. This can be done with incredibly limited runout. It's not the first time someone has lengthened or shortened a shaft. Don't be so surprised that other people know what they're doing. Just because you have no experience in fabrication or a machine shop doesnt mean things are impossible or a bad idea. It's actually really easy.

 

Yes, we will dynamic spin balance if the static balance indicates a need to....

As for the shaft spinning 1/2 engine RPM, remember there is primary reduction from crank to.clutch basket, then another reduction at the final drive where the shaft goes 90° from the trans. I dont have the ratios in front of me but Im fairly certain the shaft isnt running over 4500rpm.

But even if it DOES were talkin about a small diameter shaft with a low moment of inertia and also it is very short which makes it very stiff relative to a 3-4" dia. hollow, 48"+ long car shaft....

As for how long, I dont know yet, thats why we are doing a proof of concept project. Im thinking 7-10 days taking my time and getting the procedure nailed down to provide consistently repeatable results... Once the jig(s) are made it shouldnt take more than a couple hours...

Jay

 

To Holeshot:

I was splitting cases and lacing/truing wheels when I was 10. I built my first stroker on my own machines using custom Wiseco pistons designed by me with Autocad when I was 16.. I took a 94 YZ125, bored it 6mm over, re-nickasil'd cylinder, stroked the crank 6.5mm using a banshee rod (13mm longer than YZ and smaller wrist pin) and TIG welded 13mm to the bottom of cylinder one bead at a time, hammer peened between each pass to stress relieve the heat affected zone.... Net result: 174.5cc displacement with 180# compression and 37-38hp on gas and 41-42 on alcohol...

I put over 3000 hard race miles on it w/no failures in fact it still runs today.

My point? I know what Im doing to perform mods safely. Ive probably forgot more about performance mods/fabrication/engines than most people ever learn....

Thanks for the safety concerns, its always on my mind when working on someone elses machine

Jay

 

I am ready to send the parts to you, let me know where to send.

~M

 

I had a machinest friend stretch my shaft 5 1/2" a few years ago and had no viration even at a 100 mph+.

 

Pathbert, do you have a link to a build thread for your bike? I have a 82 maxim750 that I would like to stretch, as my 6'1'' frame is a little cramped riding it down the road! Please pm me with whatever info you can provide on your build!

 

Guess we scared him away. I offered parts and have never heard a word.

 

That's a very tidy-looking bike. I always liked the sweep of the 1100's tank and I find it really "pops" the way you have the bike set-up. Kudos...

 

You can go to my profile to see the original thread.