RB head on L-Gata

atomman

Club Member
Gear drive instead ?

RB-L gear drive.JPG

Need to play round more with gear MOD's this is 2.5 , 24 teeth & 48 on Cam drive to get the 2:1 ratio , maybe more teeth/bigger to use less gears like the one BumbleJon posted, Its all a bit of guess work though as until I can get to some machines but can still try and package it all in for now
 
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Mark N

Club Member
Gear drive instead ?

View attachment 38586

Need to play round more with gear MOD's this is 2.5 , 24 teeth & 48 on Cam drive to get the 2:1 ratio , maybe more teeth/bigger to use less gears like the one BumbleJon posted, Its all a bit of guess work though as until I can get to some machines but can still try and package it all in for now

Isn't that set-up going to have the cams turning the opposite direction to the crank?
 

atomman

Club Member
Isn't that set-up going to have the cams turning the opposite direction to the crank?

Yes good spot but there is an idler gear behind cam drive to flip the direction,

its already changed a few times since that mock up
 

jonbills

Membership Secretary
Site Administrator
what's the advantage of gear drive over a chain? looks a bit Heath-Robinson.
 

Mark N

Club Member
Just a thought, but is there room at the base of the head to fit a twin idler sprocket (similar to the KEW set-up), holding the chain central and run a single chain?
You would also need a positive offset on the cam sprockets if space allows.
 

atomman

Club Member
The main problem is that the cam drives stick out to far to get a straight run for one chain, even if I machine the head a bit and offset the cam sprockets ,
 

atomman

Club Member
what's the advantage of gear drive over a chain? looks a bit Heath-Robinson.

From my small knowledge, chains tend to stretch and also at higher revs whip and move the timing around , gears don't but you get more mechanical loses through them , both transmit harmonics but the best option seem to be a belt like the RB original , but I cant use that because of the oil situation in the front cover .
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
Interesting Thread.

Are you doing this for a challenge or for improved performance?

If for a challenge then you certainly have one. I can't help thinking that the cams should ideally be belt-driven but if not then chain. Gears would be noisy, sap power and wear out. You would end up with a lot of slack.

If for power isn't the single cam a lot easier? I love that single cam crossflow engine. Also why go to all this trouble on a 2.4 standard bottom end? If you intend to modify the bottom end the cost of all this would buy you a proven stroker.

In conclusion if it's for fun and a challenge fair play, great project.
 

atomman

Club Member
Interesting Thread.

Are you doing this for a challenge or for improved performance?

If for a challenge then you certainly have one. I can't help thinking that the cams should ideally be belt-driven but if not then chain. Gears would be noisy, sap power and wear out. You would end up with a lot of slack.

If for power isn't the single cam a lot easier? I love that single cam crossflow engine. Also why go to all this trouble on a 2.4 standard bottom end? If you intend to modify the bottom end the cost of all this would buy you a proven stroker.

In conclusion if it's for fun and a challenge fair play, great project.


Bit of both Rob to be honest , single cam head would easier, but have you tried finding one ? the twin cam head was cheap and just down the road and should flow better to and has decent chamber cc of 39.

OS Giken use gear drive and it revs to 1ok . (they do have a counter weight crank etc, etc)

why the l24 ? well its spare and the head was off it already, shorter stroke L24 crankshaft should rev better
 

peter_s

Club Member
I can't help thinking that the cams should ideally be belt-driven but if not then chain. Gears would be noisy, sap power and wear out. You would end up with a lot of slack.

I would expect a well setup gear system to last the lifetime of the engine.

There are tons of early cars that had gear driven OHV system. Bugatti and other early sports/racing cars. I wonder how they held up.
 
Bit of both Rob to be honest , single cam head would easier, but have you tried finding one ? the twin cam head was cheap and just down the road and should flow better to and has decent chamber cc of 39.

OS Giken use gear drive and it revs to 1ok . (they do have a counter weight crank etc, etc)

why the l24 ? well its spare and the head was off it already, shorter stroke L24 crankshaft should rev better

Well done for keeping it L24, it'll 'feel' right. Regarding gear's sapping power, most high revving/performance motorcycle engines(wsb/motoGP) have had gear driven camtrains for some while now, I think you can handle the 1bhp loss for the accuracy and reliability it'll deliver, on my bike engines they've never been an issue.
 

Rob Gaskin

Treasurer
Staff member
Site Administrator

atomman

Club Member
been doing some reading about various cam drive systems , some great idea's and i'm gonna do a few more models to have a look,

Here's some quick different designs i found ,
7774181_orig.jpg 126-7.jpg 9756806_orig.jpg
 

atomman

Club Member
here's a quick mock up with some bevel drives and a shaft to join up to the cams ,
RB-L bevel drive.JPG

Needs another shaft support block , and some other work, but could be a solution to package it in the room available in the OG front cover , of course these are ideas i'm just putting up here and are no way finished or FMEA'd etc , I'm just chucking everything up here 'warts an all' to show you all the thought process.
 

Mark N

Club Member
here's a quick mock up with some bevel drives and a shaft to join up to the cams ,
View attachment 38628

Needs another shaft support block , and some other work, but could be a solution to package it in the room available in the OG front cover , of course these are ideas i'm just putting up here and are no way finished or FMEA'd etc , I'm just chucking everything up here 'warts an all' to show you all the thought process.

If you go that route, you will most likely lose your oil pump drive.
If that doesn't concern you, why not space the lower drive sprocket as far forward as you can and see if you can go single chain (RB routing).
 
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