V&H Billet Clutch Basket Question

[sam78gs750]

so... ummm... I beat the hell out of my bike. Run it close to redline, powershift all the time.... should I be worried about my clutch blowing up in a huge mushroom cloud here? Angled gears???

[posplayr]

Explain to me then why in EVERY high horse drag car & motorcycle transmission uses straight cut gears in the transmissions? Pro Stock cars, at 500 cubic inches ae making almost 1500 hp & OVER 1000 lbs of torque & ALL use straight cut gears. Same with transmissions in Pro Stock bikes & Top Fuel & Funny Bikes. Ray.

Ray I know that is a rhetorical question, but I'll try and explain the apparent paradox anyway.


a.) The straight cut gears are used primarily because they have much less drag than a Helical gear. The Helical gear faces slide against one another when they meet and there is more friction (I can't quantify that but I'm sure if there are some ME's here they covered that in class).

b.) The straight cut gears have no side force thrust, which again reduces frictional forces (i.e. on thrust bearings)

a.) and b.) make straight cut gears more efficient (less lost torque in friction)

c.) The helical gears are quieter, I think if you back up your car you will hear a reverse spur gear making extra noise. On the GS the smaller gear on the clutch hub is not that small in relation to the driving gear on the crank so straight cut GS gears as not as bad from a noise perspective. Of course with 1500 hp who could tell ?

d.) Finally the issue of strength. That is more complicated but all else being equal, the helical gear can handle more torque because there is more effective thickness to the helical tooth v.s the spur gear tooth. Stiffness normally increases to a power (like third power) of thickness and the helical gears as at an angle at the point of mesh so it is logical to assume there is a higher stiffness and the gear teeth will sustain a higher total load assuming thrust can be dealt with.

e.) There is another issue of fatigue life, where the helical gears are more likely to encounter high mileage and the 1500 hp machines you are speaking of never likely get to 100K miles. So the cumulative stress of the straight cut gears see if much less than the helical cut.

Jim

[Nessism]

Yea, what Jim wrote...

Helical gear tooth size is larger, which makes it stronger. The gradual tooth engagement also makes it quieter and smoother. Problem is thrust loads.

[gs road racer]

Yea, what Jim wrote...

Helical gear tooth size is larger, which makes it stronger. The gradual tooth engagement also makes it quieter and smoother. Problem is thrust loads.

Ditto that Ed the engineers made a compromise in these motors that way. Unfortunately for us that's created some problems with the thrust even in stock form. It did make them quieter until the clutch basket damper springs break and make a hell of a racket...sounds like it's gonna jump out and bite ya! The mention of very high horsepower drives using straight cut gears because of strength? NO because the thrust loads would be unmanageable.Well maybe not no in fact the helically cut gear has less engagement/contact surface then the straight cut gear (this is an argument that should be taken as a question to an engineer).The helical gear transmits shock better , but transmits it as thrust.

[blowerbike]

so... ummm... I beat the hell out of my bike. Run it close to redline, powershift all the time.... should I be worried about my clutch blowing up in a huge mushroom cloud here? Angled gears???

unless you own a large CC roller bearing GS.....
insert bearing models do not apply and 77-79 GS 750's have straight cut primarys and are bullet proof.
i have used the 750 gears w/ 300 + or - a few HP..
bullet proof!

this topic has wondered off its path.

[sam78gs750]

unless you own a large CC roller bearing GS.....
insert bearing models do not apply and 77-79 GS 750's have straight cut primarys and are bullet proof.
i have used the 750 gears w/ 300 + or - a few HP..
bullet proof!

Very well....I'll continue to ride it hard with no clutch mods. Thanx for the info and peace of mind

this topic has wondered off its path.

given my previous comment I obviously have nothing to contribute to this topic... I just got a little shook by all this talk about powershifting and blowing out clutch baskets Sorry about the thread jack. Back to the V&H clutch basket, what he'll need and what it'll cost.

[TheCafeKid]

so... ummm... I beat the hell out of my bike. Run it close to redline, powershift all the time.... should I be worried about my clutch blowing up in a huge mushroom cloud here? Angled gears???

No, your bike came from the factory with straight cut gears. Thus, no side load.. the 77-79 750 TO MY KNOWLEGE, is the ONLY GS with this gear set stock..Maybe the 1150? But I dunno..

[quexpress]

i have used the 750 gears w/ 300 + or - a few HP..
bullet proof!

How is this done? Are the gears removed from the 750 crank and clutch basket, and then installed (welded I guess) on the 1100 items?

[rapidray]

1150 has helical clutch hub gears too. Ray.

[rapidray]

How is this done? Are the gears removed from the 750 crank and clutch basket, and then installed (welded I guess) on the 1100 items?

Yes, the 750 clutch hub gear & crank gear are installed on the 1100 clutch hub & crank. I just did a 1229 street motor for streetracer1150 with 750 gears & there is some clearancing that needs to be done inside the 1100 cases to get the clutch gear to clear. About 30 minutes work. BIG difference in clutch tunability on a high hp motor but you also use 5-7 FEWER teeth on the rear sprocket so less chain to spin! Ray.

[TheCafeKid]

1150 has helical clutch hub gears too. Ray.

Cool, wasnt sure. Learning every day

[quexpress]

Yes, the 750 clutch hub gear & crank gear are installed on the 1100 clutch hub & crank.

What's a ball park figure ($) to get straight cut gears installed on a crankshaft?
Thanks!

[Nessism]

First Timer posted some photos in his GS1000 rebuild thread where he had a crank rebuilt by Stan Gardener (spelling?) and it cost something in the $500 range.

[quexpress]

First Timer posted some photos in his GS1000 rebuild thread where he had a crank rebuilt by Stan Gardener (spelling?) and it cost something in the $500 range.

Thanks!

[Big Jay]

First Timer posted some photos in his GS1000 rebuild thread where he had a crank rebuilt by Stan Gardener (spelling?) and it cost something in the $500 range.

And he's the best