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

[Captain]

 1/ It's a pair of ball bearings complete with oil feed.
 2/ There is a difference with the primary damper gear and there are issues with how it is supported that forced me to manufacture our own replacement (I exploded the OEM primary gear). Your comments about not seeing why Honda would machine a gear this way mandated an answer in my investigation into the feasibility of this project and without trying to sound arrogant or dismissive it is not simple and easy and if you try just duplicating the tooth form of the OEM gears you will not be able to hear yourself nor the engine running over the gear drive during operation. This is because you will have no practical in-volute tooth profile to transfer the power smoothly and you will be (in basic terms) operating gears that are acting like paddles and with excessive impact of each tooth as it rotates. This will lead to eventual failure.

 To sum this all up, it is not easy and if it was it would have been attempted many-many years ago and to my knowledge what I have created is the first successful conversion in all this time. Further I am assisting Keith  (kmb69) with the parts for his project/s commercially.

 Captain   

[kmb69]

.....
Further I am assisting Keith  (kmb69) with the parts for his project/s commercially.

 Captain   

I did not mean to imply in a previous post that Brent was subsidizing my efforts monetarily but rather technically - SUBSEQUENT to my sending "CUBIC DOLLARS" to NZ for parts. The costs of my project so far is staggering and definitely not for the faint of heart.    Don't tell my wife! 

Undoubtedly, Brent has spent tens of thousands of dollars, and untold blood, sweat, and tears to develop this solution for the DOHC and one should not expect him to be an open book on the subject without substantial investment on any of your part IMHO. 

[Jerry Rxman Griffin aka MuthaF'er]

This #$%* is DEEP!     Keep up the great research boys. Very interesting reading. Think I'll just simply turn a wrench or two. 

[Captain]

This #$%* is DEEP!   

I never thought of it like that LOL..... But when you have a problem and no one else has a solution then some serious time and effort is required in order to engineer a successful outcome.

 When you do then the results are worth it and exactly that has happened here.

 Captain

[Medyo Bastos]

I agree with jerry! This is way over my head, but great reading! Keep up the good work🤙


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[gschuld]

I agree with jerry! This is way over my head, but great reading! Keep up the good work🤙


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Exactly.... 

[754]

I am pretty sure there should be clearance at the tooth tip, of that left gear.
 So you are saying you are using the hyvo  driver teeth, which are not regular involute form,  dumping some big HP through them , and they are holding up ? How many hours are you thinking? Race only with frequent changes, or streetable number of hours ?

[MessnerMoto]

1/ It's a pair of ball bearings complete with oil feed.
 2/ There is a difference with the primary damper gear and there are issues with how it is supported that forced me to manufacture our own replacement (I exploded the OEM primary gear). Your comments about not seeing why Honda would machine a gear this way mandated an answer in my investigation into the feasibility of this project and without trying to sound arrogant or dismissive it is not simple and easy and if you try just duplicating the tooth form of the OEM gears you will not be able to hear yourself nor the engine running over the gear drive during operation. This is because you will have no practical in-volute tooth profile to transfer the power smoothly and you will be (in basic terms) operating gears that are acting like paddles and with excessive impact of each tooth as it rotates. This will lead to eventual failure.

 To sum this all up, it is not easy and if it was it would have been attempted many-many years ago and to my knowledge what I have created is the first successful conversion in all this time. Further I am assisting Keith  (kmb69) with the parts for his project/s commercially.

 Captain   

Thanks once more I will need to get deep in to this. You have much more knowledge and experience.  I will investigate this for next build... Will need to get first dohc crank

In the meantime what is the pitch of HyVo chain and width? If somebody knows

[kmb69]

.....
2/ I think I know what are you talking about. Honda did not remove all the material so probably some was left in pockets between teeth.
I would need to see how primary drive sprocket from gl1000 looks(needed for this conversion). If it was machined in same way like DOHC crank sprocket(and I dont see the reason why would HONDA machine bigger sprocket all the way if they saved on crank sprocket). Than solution is simple. I would just copy DOHC crank sprocket(leave same imperfection)... not just copy but also shorten sprocket teeth

Not even close to being that straightforward IMHO. The stock GL1000 primary sprocket works for the HyVo conversion but it is not designed to take gear to gear stress. The whole SOHC 750 5 speed primary sprocket/gear and damper system has to be redesigned to take the necessary load. The DOHC primary sprocket is one of the parts that Brent had to redesign and produce from billet to get the strength necessary to stand up to the stress. The original DOHC primary sprockets disintegrated in testing. I have a design that I think will work but it is yet untested since I have been focusing on the 750A.

[kmb69]

.....
In the meantime what is the pitch of HyVo chain and width? If somebody knows

The SOHC 750A, GL1000, DOHCs 750, 900, and 1000 use a Morse HV304. The pitch is 0.375" and is considered to be 1" wide although the outside width actually measures greater than 1".

The sprocket form is considered proprietary by Morse and requires a license from them to obtain engineering dimensions from them. Of course we reverse engineer them and can get pretty close. I have searched the internet for hours trying to find the actual sprocket specs but to no avail. Their licensees are keeping quite the lid on it. You can find the chain teeth specs usually in flat form but they are somewhat dynamic as the chain follows the sprockets.

[bwaller]

Very interesting work, good luck making this work in your A.

I'm in awe of Brent & his development, certainly this primary drive, but not only that. Crazy good stuff throughout.

It's one thing to make such development for private race use, but to offer it for sale afterward is tremendous as well.

The info sharing continues, pretty cool forum we have here! 

[RAFster122s]

I was thinking Brent was referring to Brent Waller, but clearly B.W. is not referring to himself in third person. So, whom is the Brent referring ?
Thanks!
David

[kmb69]

I was thinking Brent was referring to Brent Waller, but clearly B.W. is not referring to himself in third person. So, whom is the Brent referring ?
Thanks!
David

He is referring to Brent Hyde of Vince & Hyde Racing, New Zealand. His handle is Captain on this forum.
Lots of pictures of his creations on Facebook - Brent Hyde.

[RAFster122s]

Thank you kmb.  Ah, that company name is one I know of... a long legacy of great engineering behind that name/has came off their shelves.
Thanks for clarifying this for me.

Didn't the VFR750 around 86/87 have gear driven cams as well as the RC45, RC46, and RC51? The RC46 is of course the 5th generation VFR as the VFR800 being the RC46(2000). The RC30/VFR750R (1990) and the RVF750R/RC45 (1994)
 (Not adapting the VFR gear drive of course as they are radically different motors)
That is the path being discussed here, right? (Developing a gear driven camshaft for the DOHC and SOHC750A motors...or at least that is where the engineering has been applied so far.)
Eliminating the timing chain provides a positive engagement wof crank to cam without any risk of timing jumping that results in engine damage or destruction, or the cam timing walking a tooth forward or back...the later while not necessarily resulting in damage it would affect performance negatively requiring disassembly to some degree to rectify the problem.

Following Brent's race bike development the past several years he went through a period of timing chain tensioners breaking and it took quite some time to find a solution that did not require new tensioners after every race weekend. If a gear drive solution were allowed in his race class it would allow pushing the rpms up on the motor without fear of cam timing changes or cam timing changed from sudden rear wheel lockup.

[kmb69]

.....
That is the path being discussed here, right? (Developing a gear driven camshaft for the DOHC and SOHC750A motors...or at least that is where the engineering has been applied so far.)
.....

No. The discussion here is related to the primary drive - crankshaft to primary shaft.

[scottly]

The Morse HV sprocket does have an involute tooth form. The Morse SA (silent) sprocket does not.

[MessnerMoto]

The Morse HV sprocket does have an involute tooth form. The Morse SA (silent) sprocket does not.

I think Brent wanted to say that that HyVo gears in engine are not "standard" involute gears and that they are not machined correctly by Honda because of saving time. Maybe I misunderstood it....

This is how sprockets would look in sohc.(Modulus 3, pressure angle 20). But like Brent sad I would need to look how sprockets differ from this standard  involute gears...

[livefast_dieold]

Super interesting thread!

I was not aware that HyVo chains have involute gears... time to find a cb750a crank!

BTW, maybe I'm totally crazy with this, what about honing down the chain teeth on a regular cb750 crank, and then machining proper involute gear on the base that remains? I'm concerned that it won't be feasible for 3 main reasons: 1. not enough space for the gear cutting tool, 2. the heat treatment will severely distort the crank, 3. the resulting gear will be too small

[kmb69]

The Morse HV sprocket does have an involute tooth form. The Morse SA (silent) sprocket does not.

I think Brent wanted to say that that HyVo gears in engine are not "standard" involute gears and that they are not machined correctly by Honda because of saving time. Maybe I misunderstood it....

This is how sprockets would look in sohc.(Modulus 3, pressure angle 20). But like Brent sad I would need to look how sprockets differ from this standard  involute gears...

You are correct about what Brent said.

Pretty sure the Honda HyVo sprockets are closer to Mod 2.75 and apparently have "shifted" teeth profiles. Also, the gear gurus tell me the crank gear and the idler gear should not have the same number of teeth. It has to do with wear as the same teeth are always engaging one another and something about harmonics. Some of this shifted profile stuff is a bit tough for me to thoroughly grasp but I keep on plugging away and depending on the gear gurus for advice.

The DOHC 900/1000 has 28 teeth on both the crank and primary so Brent's 23 tooth idler solves the wear and harmonics issue and the ratio stays the same. Both the SOHC 750A and DOHC 750 have 24 teeth on the crank and 28 teeth on the primaries. The SOHC 5 speed has 24 teeth on the crank and 41 teeth on the primary as you have drawn but I think you will need an odd number of teeth on your idler which will change the primary ratio a bit.

[kmb69]

The Morse HV sprocket does have an involute tooth form. The Morse SA (silent) sprocket does not.

The cam chains are usually manufactured by DID under license from Morse/Borg-Warner. They are 6.35mm (0.25") pitch and come in 3 different widths. According to the DID catalog, DID states on page 106, that these chains also use an involute tooth form on the sprockets. See attached PDF.

[kmb69]

I know from reverse engineering the cam chain teeth on the Honda crankshaft they have some kind of involute tooth form - they are not straight sided. I also know the tooth form is somewhat different on the cam shaft sprocket. Maybe because of the difference in diameter. But it is not straight sided.

[scottly]

The SOHC 5 speed has 24 teeth on the crank and 41 teeth on the primary as you have drawn but I think you will need an odd number of teeth on your idler which will change the primary ratio a bit.

Changing the number of teeth on the idler has no effect on the ratio. For example, if the crank and primary sprockets both have 20 teeth, and the idler has 40 teeth, for each revolution of the crank the idler would turn 1/2 a revolution, and the primary would turn one revolution, for a ratio of 1:1. If all three gears have 20 teeth, for each rev of the crank, both the idler and primary will turn one revolution; the ratio is the same 1:1.

[MessnerMoto]

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

[kmb69]

The SOHC 5 speed has 24 teeth on the crank and 41 teeth on the primary as you have drawn but I think you will need an odd number of teeth on your idler which will change the primary ratio a bit.

Changing the number of teeth on the idler has no effect on the ratio. For example, if the crank and primary sprockets both have 20 teeth, and the idler has 40 teeth, for each revolution of the crank the idler would turn 1/2 a revolution, and the primary would turn one revolution, for a ratio of 1:1. If all three gears have 20 teeth, for each rev of the crank, both the idler and primary will turn one revolution; the ratio is the same 1:1.

Duh, you are correct. I knew that.   I must have been drinking when I wrote that! 

[kmb69]

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?