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Author Topic: Geared Primary Drive  (Read 35590 times)

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Offline MessnerMoto

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Geared Primary Drive
« on: April 21, 2018, 12:39:12 pm »
Long story short for people who are not familiar with the topic, this is a path to eliminate chain driven primary drive... It will be compatible with cb750A and DOHC cb750 cranks... This is a current state of progress. This was done 2 months ago... I still did not have time to come with good solution for idler carrier. Next step is to 3d scan lower crank case. This will give me better overview of the situation. The biggest question is were and how to attach idler carrier to bottom case(maybe upper?)
« Last Edit: April 21, 2018, 12:40:51 pm by MessnerMoto »
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Offline Medyo Bastos

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Re: Geared Primary Drive
« Reply #1 on: April 22, 2018, 02:22:07 am »
...the only thing I can say is, WOWWWW!


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Offline madmtnmotors

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Re: Geared Primary Drive
« Reply #2 on: April 22, 2018, 08:12:06 am »
Impressive! Definitely keep us posted!  8)
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Offline MessnerMoto

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Re: Geared Primary Drive
« Reply #3 on: April 22, 2018, 11:26:11 am »
Thx!

The most difficult part remains and thats to think how to bolt/attach carrier to crank case
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Online PeWe

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Re: Geared Primary Drive
« Reply #4 on: April 22, 2018, 11:42:38 am »
There are always things to do on our CB750's. The job is never ending ;)
When bike is running fine, time for improvement!!
This forum is a good source of interesting  and good ideas.
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Offline Old Scrambler

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Re: Geared Primary Drive
« Reply #5 on: April 23, 2018, 06:50:57 pm »
Mounting blocks may need to be externally supported on both cases and might be braced against the crank. I am visualizing a pair of 3-legged blocks holding the idler-shaft in addition to end-shaft mounts to the side-walls of the cases.
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Offline MessnerMoto

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Re: Geared Primary Drive
« Reply #6 on: June 12, 2018, 09:10:07 am »
Just to give small update.... I am occupied with cam tensioner system production.... But things are also getting done for geared primary drive

I have and idea where to put holder for idler gear inside of the lower case.

I had to 3d scan lower case to get precise measurements. Error of the 3d scan is 0.3mm.

Next step is to fit in the idler holder....

Enjoy the pics ;)

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Offline kmb69

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Re: Geared Primary Drive
« Reply #7 on: June 12, 2018, 05:30:51 pm »
Quote from: MessnerMoto on June 12, 2018, 09:10:07 am
.....
I had to 3d scan lower case to get precise measurements. Error of the 3d scan is 0.3mm.
.....

That's pretty darn accurate. I get the same error with my scanner over 421mm. I need a larger calibration board for parts this size.

Nice pictures.
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Offline jgger

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Re: Geared Primary Drive
« Reply #8 on: June 12, 2018, 09:51:11 pm »
If you run a single idler gear won't the clutch/Trans spin backwards?  I know you didn't say you were using a single gear....just wondering.

This is a cool project and very interesting, keep up the good work.
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Offline 754

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Re: Geared Primary Drive
« Reply #9 on: June 12, 2018, 11:29:31 pm »
Sprockets run same direction, two gears together run opposite directions.
 Add an idler, then both shafts turn same direction.
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Offline MessnerMoto

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Re: Geared Primary Drive
« Reply #10 on: June 13, 2018, 01:25:00 am »
Quote from: 754 on June 12, 2018, 11:29:31 pm
Sprockets run same direction, two gears together run opposite directions.
 Add an idler, then both shafts turn same direction.

thats correct

Quote from: kmb69 on June 12, 2018, 05:30:51 pm
Quote from: MessnerMoto on June 12, 2018, 09:10:07 am
.....
I had to 3d scan lower case to get precise measurements. Error of the 3d scan is 0.3mm.
.....

That's pretty darn accurate. I get the same error with my scanner over 421mm. I need a larger calibration board for parts this size.

Nice pictures.


no comes difficult part to make everything work. I will have to run some FEA analysis also to see if its going to hold.
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Offline jgger

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Re: Geared Primary Drive
« Reply #11 on: June 13, 2018, 05:23:33 am »
Quote from: 754 on June 12, 2018, 11:29:31 pm
Sprockets run same direction, two gears together run opposite directions.
 Add an idler, then both shafts turn same direction.

And I knew that, had an old man moment there. But I did prove that there Is  such a thing as a stupid question!

I'll just sit back and quietly watch  now. Haha!
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Offline dragracer

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Re: Geared Primary Drive
« Reply #12 on: June 13, 2018, 11:14:33 am »
Looks like a viable solution to the primary issue for anyone desiring the use of a dohc crank. The cost to purchase this setup will likely be a major deterrent to most of us racing on a tight budget. Nevertheless, thanks very much for your concerted efforts in bringing this conversion to fruition. We now have a potential option to choose from in our quest for more horsepower.
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Offline MessnerMoto

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Re: Geared Primary Drive
« Reply #13 on: June 13, 2018, 12:34:42 pm »
Quote from: dragracer on June 13, 2018, 11:14:33 am
Looks like a viable solution to the primary issue for anyone desiring the use of a dohc crank. The cost to purchase this setup will likely be a major deterrent to most of us racing on a tight budget. Nevertheless, thanks very much for your concerted efforts in bringing this conversion to fruition. We now have a potential option to choose from in our quest for more horsepower.

Should not be to expensive
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Offline slikwilli420

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Re: Geared Primary Drive
« Reply #14 on: June 13, 2018, 01:15:36 pm »
Cost is the question of the day on all of these things. I would say that if it could show a measurable power increase along with additional longevity/durability then it would be more interesting.
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Offline simon#42

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Re: Geared Primary Drive
« Reply #15 on: June 14, 2018, 01:19:57 am »
i doubt there will be any power increase , but this is sill a great idea . having a chain thrashing around with no proper form of tensioning is a crap idea .
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Offline MessnerMoto

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Re: Geared Primary Drive
« Reply #16 on: June 14, 2018, 01:41:12 am »
Yes it will not increase the power for sure... Maybe some because it will eliminate some loses in transfer from cank to transmission.

But it will be much reliable and it will handle bigger power outputs than chain system. No modern bike is using chain system(not talking about current harley:D)... Manufacturers eliminated primary chain system is mid 80'

Also primary chain system is one of bottlenecks for higher rev range...
Primary damper unit I have designed will also handle much more abuse and it will last longer....
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Offline turboguzzi

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Re: Geared Primary Drive
« Reply #17 on: June 14, 2018, 03:10:51 am »
honda put it on the RCBs for endurance racing reliability rather than power gains

funny, now that i think of it, cant really pin point who was the first inline four to have a gear on one of the crank webs in a mass production bike

my decaying memory says 1980 GSX750E

other bets?

little trivia contest :)
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Offline livefast_dieold

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Re: Geared Primary Drive
« Reply #18 on: June 14, 2018, 04:50:32 am »
Quote from: turboguzzi on June 14, 2018, 03:10:51 am
honda put it on the RCBs for endurance racing reliability rather than power gains

funny, now that i think of it, cant really pin point who was the first inline four to have a gear on one of the crank webs in a mass production bike

my decaying memory says 1980 GSX750E

other bets?

little trivia contest :)

1978 Kawa KZ1000 :-)
« Last Edit: June 14, 2018, 04:52:29 am by livefast_dieold »
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Offline simon#42

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Re: Geared Primary Drive
« Reply #19 on: June 14, 2018, 05:10:44 am »
kawasaki z1 which i think was 72  , the suzuki gs 1000s where gear driven not sure about the 750,s
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Offline simon#42

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Re: Geared Primary Drive
« Reply #20 on: June 14, 2018, 06:59:18 am »
just had a look in the garage and i have a 1971 mv agusta 750 engine which has a gear driven primary . cant think of anything earlier off hand , but im sure someone will !
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Offline livefast_dieold

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Re: Geared Primary Drive
« Reply #21 on: June 14, 2018, 07:35:46 am »
Quote from: simon#42 on June 14, 2018, 06:59:18 am
just had a look in the garage and i have a 1971 mv agusta 750 engine which has a gear driven primary . cant think of anything earlier off hand , but im sure someone will !

Well then: 1966 Mammoth Munch!
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Offline 754

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Re: Geared Primary Drive
« Reply #22 on: June 14, 2018, 07:58:31 am »
Pretty sure Z1 had it.
 IIRC our 750 tranny run in reverse because of the primary chains, then using a layshaft to change direction for the output shaft. A step I assume the Other I4,s did not have an perhaps part of why most motors  seem shorter or more compact than ours.
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Offline kmb69

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Re: Geared Primary Drive
« Reply #23 on: June 14, 2018, 08:15:48 am »
Quote from: MessnerMoto on June 14, 2018, 01:41:12 am
Yes it will not increase the power for sure... Maybe some because it will eliminate some loses in transfer from cank to transmission.
.....

Quote from: turboguzzi on June 14, 2018, 03:10:51 am
honda put it on the RCBs for endurance racing reliability rather than power gains
.....

Brent's onboard data collection indicates their gear drive DOHC is accelerating quicker than with the chain drive according to him.

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Offline MRieck

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Re: Geared Primary Drive
« Reply #24 on: June 14, 2018, 11:39:49 am »
Quote from: simon#42 on June 14, 2018, 05:10:44 am
kawasaki z1 which i think was 72  , the suzuki gs 1000s where gear driven not sure about the 750,s
Yes....750's too.
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