Topic: Geared Primary Drive

[Captain]

[/quote]

Also one of the reasons why I have tried to dis wade people on this forum from using welded stroker crank's in SOHC motor's.

Cheers,
Brian
[/quote]

 You are more than correct in advising any and all not to use one of these "welded strokers" nor any that have been welded/ repaired in any form.. The crank will be weakened and the durability of the same will be greatly reduced. Using the OEM drive system (chains themselves are the limit) but the crank itself can survive around the 180 RWHP level.  This means that OEM based cranks will be fine for highly developed SOHC engines as no one has achieved this on a sustainable level, but be very aware if you are road racing a turbo or are using nitro, Nos etc and your levels are above this.
 

 Captain

[Old Scrambler]

Kenny at Cycle-X broke some crank-teeth............maybe he had too much power

[scottly]

I think Kenny was using the standard SOHC chain, and there was speculation at the time that ignition may have contributed to the failure?

[scottly]

I gotta ask; what is the price tag for a billet crank?? What ever the cost, it's beyond my needs or budget, but I'm super curious.

[Captain]

I gotta ask; what is the price tag for a billet crank?? What ever the cost, it's beyond my needs or budget, but I'm super curious.

 This is development work and in progress so so I cannot tell you until it is finished.

 Captain

[scottly]

Understood. However, the SOHC guys need to understand that the Hy-Vo chain conversion with the stock auto crank is more than adequate for almost anything they can throw at it; Bear's side-car rig was VERY hard on drive trains, with the weight, methanol induced HP, and traction from a fat sticky tire.
The gear drive has more friction than the chain, so would slow Dennis' LSR bike down. The gear drive might be lighter than a chain, which *might* help Frank's drag-racer, but not by enough to justify the cost, IMHO.
Scott 

[Captain]

Understood. However, the SOHC guys need to understand that the Hy-Vo chain conversion with the stock auto crank is more than adequate for almost anything they can throw at it; Bear's side-car rig was VERY hard on drive trains, with the weight, methanol induced HP, and traction from a fat sticky tire.
The gear drive has more friction than the chain, so would slow Dennis' LSR bike down. The gear drive might be lighter than a chain, which *might* help Frank's drag-racer, but not by enough to justify the cost, IMHO.
Scott

 You are incorrect about the frictional losses and I think you may be taking my posts as some sort of negative interpretation.   All I'm doing is making available my findings, the levels of load that an OEM based crank will take (no one has ever posted this analyses/data before (that I know of)) and where that information is useful is up to the reader. I am not "throwing down" on anyone's projects, experiences or applications.
I am not trying to sell one nor the idea that it is needed for others, but in my particular case it is, so the cost is justified and so will be completed and put into service.

 Captain

[PeWe]

This thread is very interesting technically to know what and how things can be improved.

My Sohc engine will hopefully enter the 3 digit whp at next Dyno so this is way over my use or future needs.

[johno]

There is an Oz company called RPE Racing , they usually have one in stock ready to go, I think they have an add on eBay as well, for the top of the range standard crank race prep...$1,000. OZ ( US 700. )
For the new stroker crank , 70mm, 4340 chrome moly, nitrided, 7.68 kg,  etc...$2,950. (2,065 US)
I would love one 

[simon#42]

thats very cheap i paid almost twice that to have a twin cylinder bmw crank made .

[johno]

Simon,
Cheap for you is an understatement, your pommy pound is so strong now against the oz dollar they would have to pay you to take it 
1 pound = $2    so that makes a custom billet crank 1,000 pounds , now thats cheap. I could almost put up with one of your winters and lose the Ashs to get a crank that cheap 
 

[scottly]

 You are incorrect about the frictional losses

This was covered over a year ago on this thread. The gear tooth faces are rubbing against each other, while a chain "rolls" onto and off the sprockets.
 

[scottly]

There is an Oz company called RPE Racing , they usually have one in stock ready to go, I think they have an add on eBay as well, for the top of the range standard crank race prep...$1,000. OZ ( US 700. )
For the new stroker crank , 70mm, 4340 chrome moly, nitrided, 7.68 kg,  etc...$2,950. (2,065 US)
I would love one 

Thanks Mark! That's pretty much in line with what I would expect for a billet crank, maybe even lower??

[Captain]

 You are incorrect about the frictional losses

This was covered over a year ago on this thread. The gear tooth faces are rubbing against each other, while a chain "rolls" onto and off the sprockets.

Sorry but it was incorrect then and it is still incorrect now as the data you are referencing is only to 4500 RPM and it is totally different at 10000 RPM and the positions reverse.  Additional to this that in our particular case (12000 RPM) we cannot even keep the chain in it.

Captain

[Tracksnblades1]

There is an Oz company called RPE Racing , they usually have one in stock ready to go, I think they have an add on eBay as well, for the top of the range standard crank race prep...$1,000. OZ ( US 700. )
For the new stroker crank , 70mm, 4340 chrome moly, nitrided, 7.68 kg,  etc...$2,950. (2,065 US)
I would love one 

Last time I tried to contact RPE (Australia) their e-mail was inactive. Their telephone number was no longer in service. Their place of business was reported closed permanently.

I did send the eBay seller a message and received a response. But, as I understood the billet crank offering was double roller chain as the OEM one. The seller had matching shorter "Carrillo style" rods in another listing.

However, I would rely on your own personal research....

Caveat Emptor

[dragracer]

I know I can't justify a billet crank for a motorcycle engine that'll never see an 8 second pass. Hopefully Mirkos proposed primary will hold up with the stock sohc crank in a drag racing engine. I'll have to wait until he reignites his design process to see whether the final product even makes sense fiscally for the return.

[kmb69]

.....
Hopefully Mirkos proposed primary will hold up with the stock sohc crank in a drag racing engine
.....

Based on what I "think" I know, I seriously doubt it. MAYBE with a DOHC crank, but the CB750A crank has an even smaller gear, 25 teeth, and the gear size on the DOHC crank is part of the problem Brent is having, not to mention the base material of both cranks is crapola! It's gonna take a billet crank, IMHO, and they won't be cheap.

[dragracer]

.....
Hopefully Mirkos proposed primary will hold up with the stock sohc crank in a drag racing engine
.....

Based on what I "think" I know, I seriously doubt it. MAYBE with a DOHC crank, but the CB750A crank has an even smaller gear, 25 teeth, and the gear size on the DOHC crank is part of the problem Brent is having, not to mention the base material of both cranks is crapola! It's gonna take a billet crank, IMHO, and they won't be cheap.

My mistake, I meant to type DOHC crank. I guess my cell auto corrected. Well Larry, it seems if Mirko abandons his quest for a gear drive for the DOHC conversion,  personally I will probably just be content with my stock SOHC engine. I'm only bracket racing anyway so the reality for me comes down to dollars and cents .

[kmb69]

.....
My mistake, I meant to type DOHC crank. I guess my cell auto corrected. Well Larry, it seems if Mirko abandons his quest for a gear drive for the DOHC conversion,  personally I will probably just be content with my stock SOHC engine. I'm only bracket racing anyway so the reality for me comes down to dollars and cents .

Frank, I may be wrong, but I thought Mirko was working on an A crank conversion.

[scottly]

 You are incorrect about the frictional losses

This was covered over a year ago on this thread. The gear tooth faces are rubbing against each other, while a chain "rolls" onto and off the sprockets.

Sorry but it was incorrect then and it is still incorrect now as the data you are referencing is only to 4500 RPM and it is totally different at 10000 RPM and the positions reverse.  Additional to this that in our particular case (12000 RPM) we cannot even keep the chain in it.

Captain

As you don't seem to believe Morse's claims, I doubt that you paid heed to Morse's recommendations of using a pressurized lubrication system for chain speeds above 2500 FPM.

[kmb69]

.....
As you don't seem to believe Morse's claims, I doubt that you paid heed to Morse's recommendations of using a pressurized lubrication system for chain speeds above 2500 FPM.

I don't believe Morse's claims either. However, the DOHC's come stock from Honda with a pressurized lubrication system for the chain.
And the 750A's have a pressurized lube system for their chain also.

[dragracer]

.....
My mistake, I meant to type DOHC crank. I guess my cell auto corrected. Well Larry, it seems if Mirko abandons his quest for a gear drive for the DOHC conversion,  personally I will probably just be content with my stock SOHC engine. I'm only bracket racing anyway so the reality for me comes down to dollars and cents .

Frank, I may be wrong, but I thought Mirko was working on an A crank conversion.

Ahhhhhh, somehow I got confused and thought he was working on a DOHC crank conversion. 

Just curious  but has anyone exceeded the strength of the primary in a hipo 750A primary arrangement . Maybe I simply don't see how a torque converter driven engine with a low numerical ratio first gear will experience failure with a stock set up.

[kmb69]

.....
Just curious  but has anyone exceeded the strength of the primary in a hipo 750A primary arrangement . Maybe I simply don't see how a torque converter driven engine with a low numerical ratio first gear will experience failure with a stock set up.

Not broken one that I know of, but I don't believe anybody has put a really big HP A motor on the track. Mike just rebuilt Samauto's engine and he said the chain was shot. With all the gear drive snafus, I have changed plans and my 1st Automatic will use a chain. I am using a non-stock primary damper that should take some of the stress off. The stock primary damper is garbage and doesn't do much dampening.

[kmb69]

I have not machined one yet, but I have designed a new primary damper system for the 5-speed that works like and uses Goldwing rubbers for a DOHC chain crank. You know how reliable the Goldwing system is.

[scottly]

.....
Just curious  but has anyone exceeded the strength of the primary in a hipo 750A primary arrangement . Maybe I simply don't see how a torque converter driven engine with a low numerical ratio first gear will experience failure with a stock set up.

Not broken one that I know of, but I don't believe anybody has put a really big HP A motor on the track. Mike just rebuilt Samauto's engine and he said the chain was shot. With all the gear drive snafus, I have changed plans and my 1st Automatic will use a chain. I am using a non-stock primary damper that should take some of the stress off. The stock primary damper is garbage and doesn't do much dampening.

Bear was running 125+ HP with an auto crank in his sidecar rig..