Author Topic: Geared Primary Drive  (Read 2020 times)

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Offline turboguzzi

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Re: Geared Primary Drive
« Reply #25 on: June 15, 2018, 04:42:06 am »
Yes it will not increase the power for sure... Maybe some because it will eliminate some loses in transfer from cank to transmission.
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honda put it on the RCBs for endurance racing reliability rather than power gains
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Brent's onboard data collection indicates their gear drive DOHC is accelerating quicker than with the chain drive according to him.


not that i doubt the data, but at 98% efficiency for each gear coupling, you get a total of 0.98x0.98 = 96% for this setup. A silent chain can deliver over 97%. Is everything else in those engines the same?
Nothing written in stone of course, transmission efficiencies will also depend on load, speed, lubrication, but overall i find it hard to believe that it will be more efficient than the silent chain. More reliable? For sure.

Online kmb69

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Re: Geared Primary Drive
« Reply #26 on: June 15, 2018, 07:28:12 am »
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Brent's onboard data collection indicates their gear drive DOHC is accelerating quicker than with the chain drive according to him.


not that i doubt the data, but at 98% efficiency for each gear coupling, you get a total of 0.98x0.98 = 96% for this setup. A silent chain can deliver over 97%. Is everything else in those engines the same?
Nothing written in stone of course, transmission efficiencies will also depend on load, speed, lubrication, but overall i find it hard to believe that it will be more efficient than the silent chain. More reliable? For sure.

I am not an engineer so cannot speak with certainty but I think in this case it may have to do with the difference in the mass of the components. Brent's idler gear has only 23 teeth and he's running it on ceramic bearings. His gear is much lighter, has less mass, than the HyVo chain it is replacing.

Pretty sure the other big advantage has to do with maximum RPM capability. The HyVo chain has a "speed limit", if you will, before it begins to fail. They are quoted by Morse to only be good for X amount of feet/meters per minute which the implementation in the DOHC motor can easily exceed. The gear has a much higher and reliable RPM capability.

Offline simon#42

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Re: Geared Primary Drive
« Reply #27 on: June 15, 2018, 08:18:48 am »
how good was the data collection?  to be accurate both the chain and the gear drives would have to be measured under the same conditions
which means , the same tyre the same track exactly the same atmospheric conditions etc etc . when measured in a lab under identical conditions the chain is more efficient.
the differences are very small though .

Online kmb69

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Re: Geared Primary Drive
« Reply #28 on: June 15, 2018, 01:47:34 pm »
how good was the data collection?  to be accurate both the chain and the gear drives would have to be measured under the same conditions
which means , the same tyre the same track exactly the same atmospheric conditions etc etc . when measured in a lab under identical conditions the chain is more efficient.
the differences are very small though .

Not saying you're wrong, but it's hard for me to get my head around the HyVo chain being more efficient. The difference between the chain engagement friction alone, half way around 2) 28 tooth gears, versus partial gear teeth engagement of 6 teeth (counting all 3 gears)? Not to mention the additional mass of chain versus gear the engine has to spin up.

When you look at the wear marks on the HyVo gears, crank and primary, it's usually pretty significant. Look at some DOHC crank gear pictures on eBay. There's been some serious rubbing going on, engagement/disengagement! Pretty sure the HyVo efficiency goes down with increased RPM's.

Morse efficiency chart - but they're selling the stuff of course and don't chart above 4500 RPM:

« Last Edit: June 15, 2018, 01:52:27 pm by kmb69 »

Offline MessnerMoto

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Re: Geared Primary Drive
« Reply #29 on: June 15, 2018, 02:45:18 pm »
I really appreciate the discussion....

My way of thinking is also that efficiency will go down with RPM.

...this figures 97-99% of efficiency are for ideal conditions... somewhere(reliable source) I have read that that goes well below 90% in real world conditions. Compere official figures for crank HP and RW HP for cb750. Somewhere goes a lot more then 98%... Actualy there are several gear transfers and two chain transfers before it comes to rear wheel... I think this would be correct 0.98*0.98*0.98*0.98*0.98 = 90%.... but it goes more than that when you plug in official crank HP and numbers reported on rear wheel on well tuned stock cb750...

also don't forget people that this idler gear will work also with cb750 automatic crank... Direct plug and play replacement

Online kmb69

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Re: Geared Primary Drive
« Reply #30 on: June 15, 2018, 03:19:01 pm »
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also don't forget people that this idler gear will work also with cb750 automatic crank... Direct plug and play replacement

Are you designing for a 24 or 28 tooth crank gear?

You will need to change number of teeth on the idler and/or primary and/or location of idler to accommodate both.

Offline MessnerMoto

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Re: Geared Primary Drive
« Reply #31 on: June 15, 2018, 04:20:43 pm »
.....
also don't forget people that this idler gear will work also with cb750 automatic crank... Direct plug and play replacement

Are you designing for a 24 or 28 tooth crank gear?

You will need to change number of teeth on the idler and/or primary and/or location of idler to accommodate both.

24 for now. That covers cb750A crankshaft(plug and play) and cb750 DOHC crankshaft. But actually I don't see any benefits to DOHC cb750 crank...

I think most people wold like direct replacement, cb750A crankshaft because it is the easiest thing to do....

If everything works it would be easy to change number of teeth on primary drive I developed, relocate idler and lower number of teeth on idler... but there is much more work to adopt cb900 crank...
« Last Edit: June 15, 2018, 04:56:22 pm by MessnerMoto »

Offline dragracer

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Re: Geared Primary Drive
« Reply #32 on: June 15, 2018, 07:08:02 pm »
I think many of us following your gear conversion in this section are interested in using a 900DOHC crank as a performance upgrade/factory stroker crank in the sohc cases.  Not certain how many are building autos with stock cranks except for street use.

 The issue with making a 900dohc crank conversion easy and affordable has perplexed many of us for years. Your research is most appreciated.

Offline slikwilli420

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Re: Geared Primary Drive
« Reply #33 on: June 15, 2018, 07:21:01 pm »
I'd use the auto crank since I cannot stroke my engine for racing. Either way I'm watching with much interest.
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Offline scottly

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Re: Geared Primary Drive
« Reply #34 on: June 15, 2018, 08:24:43 pm »

The difference between the chain engagement friction alone, half way around 2) 28 tooth gears, versus partial gear teeth engagement of 6 teeth (counting all 3 gears)?
The flip side of this coin is that with the chain the load is spread over 14 teeth, and with gears all the load is focused on partial engagement of 2 teeth.
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Offline 754

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Re: Geared Primary Drive
« Reply #35 on: June 15, 2018, 09:20:41 pm »
Well most Inline 4s have gear drive, and they survive.
« Last Edit: June 16, 2018, 11:54:17 am by 754 »
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Offline scottly

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Re: Geared Primary Drive
« Reply #36 on: June 15, 2018, 09:37:54 pm »
How do the 750A/DOHC sprockets compare with the gears on bikes designed for gear drive, in terms of width and diameter?
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Online kmb69

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Re: Geared Primary Drive
« Reply #37 on: June 16, 2018, 05:44:03 am »
I'd use the auto crank since I cannot stroke my engine for racing. Either way I'm watching with much interest.

The DOHC 750 crank is lighter than the SOHCA crank and has a 62mm stroke. 62mm x 62mm is 748cc. Might rev quicker. Not sure how that fits your rules. Pretty sure Kenny has a cam chain and tensioner solution for the DOHC crank.


Online kmb69

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Re: Geared Primary Drive
« Reply #38 on: June 16, 2018, 05:53:59 am »

The difference between the chain engagement friction alone, half way around 2) 28 tooth gears, versus partial gear teeth engagement of 6 teeth (counting all 3 gears)?
The flip side of this coin is that with the chain the load is spread over 14 teeth, and with gears all the load is focused on partial engagement of 2 teeth.

Chain is only as strong as its weakest link. Brent is making enough horsepower to waste a chain over one weekend of racing. Granted they are forced to use the 900/1000 crank with HV304 chain. The 1100 crank uses a HV305 but Honda's heat treatment of the wider gear/sprocket causes a material failure at the #3 rod journal. They DO AND WILL break at high RPM if you're making any kind of serious horsepower.

« Last Edit: June 16, 2018, 07:21:08 am by kmb69 »

Offline slikwilli420

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Re: Geared Primary Drive
« Reply #39 on: June 16, 2018, 06:00:48 am »
I'd use the auto crank since I cannot stroke my engine for racing. Either way I'm watching with much interest.

The DOHC 750 crank is lighter than the SOHCA crank and has a 62mm stroke. 62mm x 62mm is 748cc. Might rev quicker. Not sure how that fits your rules. Pretty sure Kenny has a cam chain and tensioner solution for the DOHC crank.

Rule says stroke may not be changed. I thought the 900 crank had different stroke than the A crank. If not then that's an option.
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Online kmb69

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Re: Geared Primary Drive
« Reply #40 on: June 16, 2018, 06:11:48 am »
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Rule says stroke may not be changed. I thought the 900 crank had different stroke than the A crank. If not then that's an option.

DOHC 750 is 62mm stroke. DOHC 900/1000/1100 is 69mm stroke. So I guess you have to stay with the SOHC A at 63mm.
« Last Edit: June 16, 2018, 06:29:57 am by kmb69 »

Online kmb69

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Re: Geared Primary Drive
« Reply #41 on: June 16, 2018, 07:19:47 am »
How do the 750A/DOHC sprockets compare with the gears on bikes designed for gear drive, in terms of width and diameter?

The chain/gear/sprocket being used on the DOHC 4's, excluding the 1100, is HV304. It is a 3/8" pitch and just over an inch wide with 9/8 link plates and uses the pivot type pins. The gear/sprocket is approximately 22.5mm wide. Gear form roughly matches Module 2.75 with some adjustments to the pressure angle, addendum, and dedendum. A 28 tooth gear/sprocket is approximately 82mm in diameter. The DOHC 900/1000/1100 have a 28 tooth crank gear and a 28 tooth primary gear. The SOHC A has a 24 tooth crank gear and a 28 tooth primary gear as does the DOHC 750.

A Hayabusa in comparison has an approximately 20mm wide crank gear at approximately 123.5mm diameter with 52 teeth on the crank and a 83 tooth gear on the clutch basket. Its gear form approximates Module 2.29.

Pretty sure the Module 2.75, on properly prepared material, can handle any horsepower one could ever hope to achieve based on a SOHC 750 motor.

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Re: Geared Primary Drive
« Reply #42 on: June 16, 2018, 09:25:00 am »
What the hell did he just say?!  :o  ;) Them sum big wurds Leroy  :)
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Online kmb69

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Re: Geared Primary Drive
« Reply #43 on: June 16, 2018, 11:38:31 am »
What the hell did he just say?!  :o  ;) Them sum big wurds Leroy  :)

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Offline Captain

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Re: Geared Primary Drive
« Reply #44 on: June 16, 2018, 12:11:22 pm »
 What he is saying is that there is no problem with the tooth loading using the OEM gear form on the crank.
 To further advance this is the fact that each and every gear in the gearbox experiences multiples of the torque the crank and primary are subjected to and the gearbox gears are both smaller diameter and narrower. It doesn't take an Einstein to see this once you look rearward at the gearbox

 There just isn't an issue with the gear drive in this way and I have successfully done exactly this.

 Captain

 

Offline Captain

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Re: Geared Primary Drive
« Reply #45 on: June 16, 2018, 12:34:58 pm »
 As for the efficiency question that has been raised here, the differences at lower speeds (up to 5000RPM) are so small as to be insignificant. But beyond this then the chain starts to develop a problem as it becomes a form of flywheel and the internal loads increase to the point that at 11600 RPM (with a 28T 900 crank) the chain will begin to tear itself apart with centrifugal loads and when you add in higher engine power to this..................Chain failure is guaranteed in short order. The point here is that the Hi Vo chain is not designed with high RPM capabilities and RPM is what most race engines builders agree allows for greater HP.
 This was all in our DOHC Superbike engine, however the principals remain for what ever SOHC engine combination is being discussed here.

 Once I built the gear drive something else became apparent and that was the idler gear which replaces the chain is less than half the static weight "and" is much smaller in diameter so allows greater acceleration. Under testing we found that even using the same lightened crank but with steel rods instead of our usual Titanium ones the bike was quicker from turn to turn than it was previously. This was all recorded and confirmed with our on board ECU and the data collection it provides.

 Captain
« Last Edit: June 16, 2018, 03:14:23 pm by Captain »

Offline Sam Green Racing

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Re: Geared Primary Drive
« Reply #46 on: June 16, 2018, 01:40:03 pm »
What the hell did he just say?!  :o  ;) Them sum big wurds Leroy  :)

Come on Spanky! It's just a prescription without the squiggly signature!

hahahahaha, nice one Leroy.
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Offline dragracer

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Re: Geared Primary Drive
« Reply #47 on: June 16, 2018, 02:02:18 pm »
What he is saying is that there is no problem with the tooth loading using the OEM gear form on the crank.
 To further advance this is the fact that each and every gear in the gearbox experiences multiples of the torque the crank and primary are subjected to and the gearbox gears are both smaller diameter and narrower. It doesn't take an Einstein to see this once you look rearward at the gearbox

 There just isn't an issue with the gear drive in this way and I have successfully done exactly this.

 Captain

 

So the principles of replacing the primary chains with gears in an actual dohc engine have already been done and tested. It would be nice if all of the concepts from the sohc and dohc conversion were brought together through some cooperative efforts. On the practical side, I understand that R&D costs $$ and logically leads to proprietary safeguards. From a potential end users viewpoint, it could just be wishful thinking to see this collaboration happen in my quest to build a longer stroke / quicker, but still affordable Sohc drag bike engine.  Right now my only straight forward option is to have a stock Sohc crank stroked, and hope for the best. Not certain how many more opportunities lay ahead of me to set a new record in super eliminator given the current equipment I have on hand. I can only hope this conversion works out and is  made available to forum members at an affordable price.  Thanks again

Offline slikwilli420

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Re: Geared Primary Drive
« Reply #48 on: June 16, 2018, 03:18:18 pm »
What he is saying is that there is no problem with the tooth loading using the OEM gear form on the crank.
 To further advance this is the fact that each and every gear in the gearbox experiences multiples of the torque the crank and primary are subjected to and the gearbox gears are both smaller diameter and narrower. It doesn't take an Einstein to see this once you look rearward at the gearbox

 There just isn't an issue with the gear drive in this way and I have successfully done exactly this.

 Captain

 

So the principles of replacing the primary chains with gears in an actual dohc engine have already been done and tested. It would be nice if all of the concepts from the sohc and dohc conversion were brought together through some cooperative efforts. On the practical side, I understand that R&D costs $$ and logically leads to proprietary safeguards. From a potential end users viewpoint, it could just be wishful thinking to see this collaboration happen in my quest to build a longer stroke / quicker, but still affordable Sohc drag bike engine.  Right now my only straight forward option is to have a stock Sohc crank stroked, and hope for the best. Not certain how many more opportunities lay ahead of me to set a new record in super eliminator given the current equipment I have on hand. I can only hope this conversion works out and is  made available to forum members at an affordable price.  Thanks again

+1
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Online kmb69

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Re: Geared Primary Drive
« Reply #49 on: June 16, 2018, 10:52:26 pm »
.....
I can only hope this conversion works out and is  made available to forum members at an affordable price.  Thanks again

.....
+1

What do you guys consider affordable?

 

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