Topic: Did anyone see this? -- Honda CB750 16 Valve Twin Cam Head. Piper

[MessnerMoto]

Cheap solution wold be to find existing gear with 25 teeth for hv 304 chain

That would probably work. You may need to plan on a little more backlash than normal gearing. When you roll two HyVo gears together, they kinda "clunk" if you will and I would expect them to be rather noisy. Brent's billet idler gear runs much smoother against the HyVo crank gear than another HyVo gear does. His billet idler gear runs silky smooth against his billet primary gear. It may be because of the manufacturing method Honda used on the HyVo gears as Brent mentioned earlier. Pretty sure Brent's gears are hob milled versus Honda's broached gears.

Lets not forget that chains and tensioner in sohc are pretty noisy

[kmb69]

.....
Lets not forget that chains and tensioner in sohc are pretty noisy

That's true but Brent did some kind of "gear guru magic" to quieten the interface with the HyVo crank. 

I added to that previous post. Pretty sure a 29 tooth HyVo gear would be required.

[MessnerMoto]

Cheap solution wold be to find existing gear with 25 teeth for hv 304 chain

That would probably work. You may need to plan on a little more backlash than normal gearing. When you roll two HyVo gears together, they kinda "clunk" if you will and I would expect them to be rather noisy. Brent's billet idler gear runs much smoother against the HyVo crank gear than another HyVo gear does. His billet idler gear runs silky smooth against his billet primary gear. It may be because of the manufacturing method Honda used on the HyVo gears as Brent mentioned earlier. Pretty sure Brent's gears are hob milled versus Honda's broached gears.

Pretty sure you will need a 29 tooth HyVo gear.

Standard gear formulas don't work exactly when reversing HyVo gears. For example, using standard gear formulas, the 24 tooth crank gear calculates to Dp 9.4749 or Mod 2.68077. The GL1000 41 tooth primary calculates to Dp 8.9819 or Mod 2.82791. They use the same pitch chain. Huh? 

hmmm gl1000 primary gear has the same pitch. And same chain.(41 teeth also) Also crank sprocket on cb750 is same like on dohc 750... sprockets with same pitch should engage themselves without problem. Or I understand something wrong?

m=p/pi

where m is the module and p the circular pitch. p = 9.525 mm(3/8") in our case so for all sprockets modulus is same if they have same pitch... and m = 9.525/pi = 3.031901665900606 almost 3.00

But maybe HV chain pitch is not the same unit as gear circular pitch... nevertheless gears for same chain would have same pitch and modules no matter number of teeth

[livefast_dieold]

Question: let's say that I find a CB750 Matic crank, a GL1000 primary gear and a suitable idle gear. How do I install the idle gear in the lower gear case?

[kmb69]

hmmm gl1000 primary gear has the same pitch. And same chain.(41 teeth also) Also crank sprocket on cb750 is same like on dohc 750... sprockets with same pitch should engage themselves without problem. Or I understand something wrong?

m=p/pi

where m is the module and p the circular pitch. p = 9.525 mm(3/8") in our case so for all sprockets modulus is same if they have same pitch... and m = 9.525/pi = 3.031901665900606 almost 3.00

But maybe HV chain pitch is not the same unit as gear circular pitch... nevertheless gears for same chain would have same pitch and modules no matter number of teeth

Certainly seems like it would be that way, but apparently the HyVo chain CHORDAL ACTION dictates a change in the tooth form depending on the diameter around which it is traveling unlike a roller chain or a regular involute spur gear. So the HyVo gears do not conform to standard gear calculations in Imperial or Metric. The HyVo gears appear to have a truncated addendum or tooth form.

The HyVo gear charts that I have found indicate the HyVo gear OD is SMALLER than the HyVo gear PD (pitch diameter). Very weird but that's what they say. Examples:
P/N            Teeth    PD          OD
HV304-25   25        76mm     72.8mm
HV304-25   25        2.992"    2.866"
HV304-29   29        88.1mm  85.2mm
HV304-29   29        3.468"    3.353"

Where the standard gear OD formula is OD = (N + 2) / (N / PD)
The closest I can come up with for the HyVo is OD = (N - 1) / (N / PD)
Pretty sure there is some scaled table that is used depending on the HyVo gear diameter.

[kmb69]

Question: let's say that I find a CB750 Matic crank, a GL1000 primary gear and a suitable idle gear. How do I install the idle gear in the lower gear case?

It requires some very precise engineering and machining to develop the idler "carrier" and the same level of engineering and machining to locate the carrier in the cases. The idler "carrier" has to be precisely positioned to provide proper gear backlash for both gear pairs and it has to be mounted so rigidly that it does not move or deform the cases under load. Not to mention the necessary oil supply for the gears and their bearings. If it was easy, we would not be discussing it today. 

I should add, there is NO suitable off-the-shelf idler gear to mesh with the 750A crank and the GL1000 primary. Their tooth forms are different.

[Captain]

 HyVo tooth forms are not fully formed in-volute and are not suitable when used in direct contact (Gear - Gear).  If you read closely what I have said and the further comments by Keith you should realise that there are mulible problems to be aware of and to find successful solutions in order to create a workable Gear Drive conversion. To do this was not easy and resulted in several failures but each one provided to information to correct. Over a period of around 18 months an 10’s of $ I managed to solve the puzzle of which the very basics are listed below.
1/  Manufactured my own primary damper gear as the OEM tooth profile is below that required for effective tooth to tooth contact .......And was not strong enough in the body to support the load.
2/ Created my own idler Gear that allows smooth operation with my new primary damper gear “and” allows far more effective tooth profile contact with the OEM crank. This also is an odd number and the crank and primary are even so as to not have the same tooth to tooth contact reoccurring.
3/ Package it all into a carrier that can handle the changed directions of load and that ties the idler and primary together and minimises the crankcase loading.
4/ Anchor the whole assembly in such a way that it can withstand in excess of 10 x the operating loads.

 Captain

[slikwilli420]

Is there a ballpark idea of what this conversion will cost? Eliminating a weak spot on these engines is very attractive idea to me for being able to put more power into my racer.

[MessnerMoto]

... the only realistic solution is to buy idler gear from Brent and then make a carrier for sohc. And if I understand correctly Brent designed idler to float on oil or there is a ball bering just for idler gear? If it is floating on oil you need to modify oil pump so it can give oil to idler.. Also there need to be some welding on bottom case so you can make a place for carrier.

[kmb69]

Is there a ballpark idea of what this conversion will cost? Eliminating a weak spot on these engines is very attractive idea to me for being able to put more power into my racer.

By the time you find the proper cases, crankshaft, buy the billet parts, have the cases machined, and shipping, it is in excess of $6.5k for a DOHC 900/1000/1100.
The DOHC is not easy but it is somewhat less complicated than a SOHC 750 5 speed. Probably in excess of $8.5k for a SOHC 750 5 speed. Just guessing.
The cost for the SOHC 750A will be a little higher than the DOHC's assuming you use a DOHC 900 crank. Using the SOHC 750A crank will cost even more.

I'm not selling them so these just are ballpark numbers for piggy bank planning!     

[MessnerMoto]

Is there a ballpark idea of what this conversion will cost? Eliminating a weak spot on these engines is very attractive idea to me for being able to put more power into my racer.

By the time you find the proper cases, crankshaft, buy the billet parts, have the cases machined, and shipping, it is in excess of $6.5k for a DOHC 900/1000/1100.
The DOHC is not easy but it is somewhat less complicated than a SOHC 750 5 speed. Probably in excess of $8.5k for a SOHC 750 5 speed. Just guessing.
The cost for the SOHC 750A will be a little higher than the DOHC's assuming you use a DOHC 900 crank. Using the SOHC 750A crank will cost even more.

I'm not selling them so these just are ballpark numbers for piggy bank planning!     

If exact same idler gear would work in sohc configuration. Just 23 teeth gear in the middle. Same gear if it was normal involute gear would cost me 50$-80$ with all hardening processes and fine grinding... But I would expect that Brent would offset research and development which is normal.
All the other things needed would cost me less then 400$... making carrier on cnc.... welding support on bottom case for carrier... and machining on CNC that support to accept carrier...Modifying oil pump... But this is only if gl1000 drive sprocket will work with Brent's 23 teeth sprocket.... 

[kmb69]

... the only realistic solution is to buy idler gear from Brent and then make a carrier for sohc. And if I understand correctly Brent designed idler to float on oil or there is a ball bering just for idler gear? If it is floating on oil you need to modify oil pump so it can give oil to idler.. Also there need to be some welding on bottom case so you can make a place for carrier.

Brent's current idler gear, primary gear, and carrier only work in the DOHC cases where both the crank and primary have 28 teeth gears. Pretty sure there is no case welding in Brent's DOHC conversion. I have not dissembled mine to confirm. The idler gear runs on dual ball bearings.

Brent's 23 tooth idler gear will work in the SOHC 750A with a DOHC 900 crank since the A has the same centerline distance between crank and primary as a DOHC and it has a 28 tooth primary and since the tooth forms are very similar but it does require a different carrier. Also, the stock 750A primary damper is external to the primary shaft. It will NOT work in a SOHC 750 5 speed even with a 750A crank. Not to mention it is very doubtful a GL1000 primary conversion can carry the load and mesh with an idler gear that meshes with the crank. The GL1000 primary damper conversion is just as flimsy as the DOHC primary. It will require new billet idler and primary gears, damper, and carrier to be designed IMHO. And yes, there are gaping holes and voids in the 750 5 speed cases where the carrier has to be mounted.

And no doubt, there are $10's of thousands of R&D dollars and exploded engine dollars being amortized in the prototype/pilot parts.

[kmb69]

.....
If exact same idler gear would work in sohc configuration. Just 23 teeth gear in the middle. Same gear if it was normal involute gear would cost me 50$-80$ with all hardening processes and fine grinding... But I would expect that Brent would offset research and development which is normal.
All the other things needed would cost me less then 400$... making carrier on cnc.... welding support on bottom case for carrier... and machining on CNC that support to accept carrier...Modifying oil pump... But this is only if gl1000 drive sprocket will work with Brent's 23 teeth sprocket.... 

The centerline between crank and primary on the DOHC and SOHC 750A is 114mm versus 167mm on the SOHC 750 5 speed is why Brent's current idler gear will not work.

If you can come up with a solution for the SOHC 750 5 speed in the $2-2.5k price range, you could sell a bunch of them IMHO.

[Captain]

Here is a little unknown advantage that I uncovered when testing. We have data acquisition on our race bike and during testing discovered that the bike accelerated faster than it had done with the OEM chain drive.
This reality was due to the lower weight and diameter of the idler gear verses the chain and the mass being closer to the centre. The nett result is the Gear Drive is less power hungry to accelerate in either RPM direction and this saving in parasitic losses appears as additional power at the rear wheel.
As I said......the bike is faster out of the turns and down the straightaway.  Drag racing, road racing, street use I don’t believe that anyone wouldn’t like this feature.

Captain

[754]

 I have a bit of knowledge regarding gears, but am not a gear shop guy.
 When you say not fully formed involute, do you mean the profile is part involute, then the profile changes ?
 Or is a height thing like a stub gear having lower teeth height?

[kmb69]

I have a bit of knowledge regarding gears, but am not a gear shop guy.
 When you say not fully formed involute, do you mean the profile is part involute, then the profile changes ?
 Or is a height thing like a stub gear having lower teeth height?

They are not like standard stubs where both the addendum and dedendum are reduced approximately 75%.
They are considered involute but the dedendum appears more "normal" if you will for strength.
The addendum is definitely reduced and they usually have larger than normal tip radii.
Maybe Brent will chime in with a better description.

[Captain]

In layman’s terms the HyVo profile is in-volute but designed for the purpose of chain engagement. This results in a shallow root and a lower tip (the tooth is shorter) amongst other issues and this requires a custom designed idler gear in order to minimise this event and provide clearance and an acceptable contact area and still engage correctly with our replacement primary gear which has a fully formed in-volute tooth form.
I am not going to explain this any further as I have spent a fortune in both time and money to do this and I’m not handing over a blueprint of how it is all done. There has been enough information disclosed to show that I have achieved a successful result. Needless to say I have completed the project successfully for those that were prepared to invest without knowing a fixed price and I am proud to have supplied them with the finished product.
The next step is to see how this can be made more economical for others in the future.

 Captain

[kmb69]

.....
I am not going to explain this any further as I have spent a fortune in both time and money to do this and I’m not handing over a blueprint of how it is all done. There has been enough information disclosed to show that I have achieved a successful result. Needless to say I have completed the project successfully for those that were prepared to invest without knowing a fixed price and have supplied them with the finished product.
.....

 Captain

I VERY MUCH APPRECIATE Brent's position on this as I am sure his other investors do also.
As Brent says, myself and others ordered gear drive DOHC motors without knowing the price.
It's a very steep and expensive learning curve but the best education is not usually cheap.
Respecting Brent and the other investors, I will not be discussing the gear intricacies any further.

[MessnerMoto]

In layman’s terms the HyVo profile is in-volute but designed for the purpose of chain engagement. This results in a shallow root and a lower tip (the tooth is shorter) amongst other issues and this requires a custom designed idler gear in order to minimise this event and provide clearance and an acceptable contact area and still engage correctly with our replacement primary gear which has a fully formed in-volute tooth form.
I am not going to explain this any further as I have spent a fortune in both time and money to do this and I’m not handing over a blueprint of how it is all done. There has been enough information disclosed to show that I have achieved a successful result. Needless to say I have completed the project successfully for those that were prepared to invest without knowing a fixed price and have supplied them with the finished product.
The next step is to see how this can be made more economical for others in the future.

 Captain

Totally understandable and normal.

Mine opinion is that somebody can make this work for sohc. Maybe me:) Brent would need to provide 23 teeth idler gear(of corse for money ). No matter what is the centerline distance you can always position idler differently so it engages crank sprocket and gl1000 prim drive perfectly.... But everything else needs to be custom made for sohc...

[livefast_dieold]

In layman’s terms the HyVo profile is in-volute but designed for the purpose of chain engagement. This results in a shallow root and a lower tip (the tooth is shorter) amongst other issues and this requires a custom designed idler gear in order to minimise this event and provide clearance and an acceptable contact area and still engage correctly with our replacement primary gear which has a fully formed in-volute tooth form.
I am not going to explain this any further as I have spent a fortune in both time and money to do this and I’m not handing over a blueprint of how it is all done. There has been enough information disclosed to show that I have achieved a successful result. Needless to say I have completed the project successfully for those that were prepared to invest without knowing a fixed price and have supplied them with the finished product.
The next step is to see how this can be made more economical for others in the future.

 Captain

Totally understandable and normal.

Mine opinion is that somebody can make this work for sohc. Maybe me:) Brent would need to provide 23 teeth idler gear(of corse for money ). No matter what is the centerline distance you can always position idler differently so it engages crank sprocket and gl1000 prim drive perfectly.... But everything else needs to be custom made for sohc...

What are you going to use? CB750 A crank or DOHC crank?

@Captain: your concerns are totally understandable, keep us posted as many here would be potential buyers of a solution designed for SOHC!

[kmb69]

.....
Mine opinion is that somebody can make this work for sohc. Maybe me:) Brent would need to provide 23 teeth idler gear(of corse for money ). No matter what is the centerline distance you can always position idler differently so it engages crank sprocket and gl1000 prim drive perfectly.... But everything else needs to be custom made for sohc...

I hope you do make this work and I will buy 2.
But centerline distance definitely matters - Brent's 23 tooth gear will not engage 28-41 gears, much less 24-41.

[kmb69]

According to my calculations, the 28-41 requires a 27 tooth idler and the 24-41 requires a 29 tooth idler.

[MessnerMoto]

According to my calculations, the 28-41 requires a 27 tooth idler and the 24-41 requires a 29 tooth idler.

.... probably you are correct I draw picture with modules 3 gears.... hv gears are smaller... Can Brent make custom sprocket with his tooling ?

[kmb69]

According to my calculations, the 28-41 requires a 27 tooth idler and the 24-41 requires a 29 tooth idler.

.... probably you are correct I draw picture with modules 3 gears.... hv gears are smaller... Can Brent make custom sprocket with his tooling ?

I cannot speak for Brent but he is normally too wrapped up in his personal projects to do custom work. He keeps 50 balls in the air for his DOHC development.
It will require a custom idler and a custom GL1000 type damper gear. I seriously doubt that he would be much interested in the SOHC or have the time to do it.

[RAFster122s]

But, the question really starts with, at what power level do you start seeing issues with the chain drive causing a failure? 
Now that little bit about be faster coming out of the corners and down the straights has to be dealt with as well.  Then there is the increase in stopping power you will need to accommodate the increased speed.  So many races can be won in the corners.  The straight line speed being important as well, but getting to your straight line speed faster is going to make a large difference.


David