gear drive / chain combonation?

[crow]

I was wondering if this would be a seller if a manufacture was to make a cam drive system that was roller chain drive in front. And gear drive between the two cams.
My thinking is that the gear drive between the two cams would be completely maintenance free. just insure proper backlash. The front being a new roller chain with new style
tensioners would be forgiving to the runout issue. Hence you get the best of both worlds. It would be easy to check and replace the tensioners if ever needed with out total
teardown of the cam chest.

[NightTrain67]

The gear drive cams and chain drive cams turn in opposite directions.....Your idea would make things interesting to say the least.

[fxrp]

Yes there is but it's pricey. Wood Performance makes a 'silent belt drive.'  The inner cams drive can be geared or chain and the outer cam drive is a 5mm carbon fiber belt. We haven't installed one yet but we're putting one on my partners bar hopper this spring.

Here's a link:  http://www.woodcarbs.com/bdrive.htm

[FSG]

[Bakon]

Yes there is but it's pricey. Wood Performance makes a 'silent belt drive.'  The inner cams drive can be geared or chain and the outer cam drive is a 5mm carbon fiber belt. We haven't installed one yet but we're putting one on my partners bar hopper this spring.

Here's a link:  http://www.woodcarbs.com/bdrive.htm

Buddy races broke one of these on a really build 124. Bent stuff. Woods replaced belt, he removed set up.

[fxrp]

Buddy races broke one of these on a really build 124. Bent stuff. Woods replaced belt, he removed set up.

Broke what, the belt?

[Bakon]

Yep, that belt on the cams which can be adjusted for timing.

[fxrp]

Yep, that belt on the cams which can be adjusted for timing.

Something not right with this story. The inner drive is either OEM chain or gear, the outer drive is a cam and crank gear and a 5mm belt. There is no adjustment on the belt, just like the OEM gears you align the timing marks and install the belt. I wonder if your friend got the timing marks off.


From the belt drive manual:

STEP 21:
With both gears on but not yet torqued, align cam and crank timing marks together.
(CRANK TIMING MARK ALIGNED WITH THE SINGLE DOT CAM TIMING MARK.
THIS WILL PLACE THE #2 CYLINDER, OR REAR CYLINDER, ON ITS
COMPRESSION STROKE. (See picture #6) Start by placing timing belt on ......
...... Once you have the belt on the cam gear â€"check cam and crank timing
marks and make sure they are still aligned. ..............Make sure timing belt is flush
with end of cam and crank gear. â€" CHECK TIMING MARKS AGAIN!



[attachment removed after 60 days by system]

[Admiral Akbar]

"Something not right with this story. The inner drive is either OEM chain or gear, the outer drive is a cam and crank gear and a 5mm belt. There is no adjustment on the belt, just like the OEM gears you align the timing marks and install the belt. I wonder if your friend got the timing marks off."

I'd bet that the 4 bolts on the cam pulley allow the use of offset buttons..

Max

[FSG]

The pic shows Advance / Retard Timing Marks and the Parts List also shows the Camshaft Spider Hub to have Elongated Holes and Timing Marks.

[DaleW]

The gear drive cams and chain drive cams turn in opposite directions.....Your idea would make things interesting to say the least.

surely it wouldnt make any difference if the lobes are symmetrical

[PoorUB]

surely it wouldn't make any difference if the lobes are symmetrical

Want to rethink that?
While certainly possible, (obviously!), it takes new cams, with the proper lobe placement for the reverser rotaion, of the front cam. The rear cam rotates the same as a typical chain drive, and possibly is no differant. The front cam is reverse rotation and is a odd ball. If you look at FBSG's post you see that the front cam rotates the same whether gear drive or chain, but with the "combo" drive the front cam rotates opposite.

[DaleW]

of course the driven cam will need to be retimed to the driving cam,but t6hats just a detail.

[fxrp]

The pic shows Advance / Retard Timing Marks and the Parts List also shows the Camshaft Spider Hub to have Elongated Holes and Timing Marks.

You're right, but there is no mention of cam advance/retard in the text of the installation proceedures. Could have been user error.

Paul

[FSG]

You're right, but there is no mention of cam advance/retard in the text of the installation proceedures. Could have been user error.

Paul

From the BD Manual , but probably still user error.

[fxrp]

You're right, but there is no mention of cam advance/retard in the text of the installation proceedures. Could have been user error.

Paul

From the BD Manual , but probably still user error.

I should slow down and read closer.  But if you wanted to advance or retard the timing, why "start" with the marks at zero? Once you torque the bolts the timing is set. Maybe Bobby needs to edit the manual a little; and like I need to read it a little closer 

Paul

[FSG]

I should slow down and read closer.  But if you wanted to advance or retard the timing, why "start" with the marks at zero? Once you torque the bolts the timing is set. Maybe Bobby needs to edit the manual a little; and like I need to read it a little closer 

Paul

The manual is going to be written from the initial installation perspective and I'd expect any advance/retard to be done after the install, although if the installer knew what they were doing then there's no reason it couldn't be done at the same time, but I wouldn't.

[fxrp]

I should slow down and read closer.  But if you wanted to advance or retard the timing, why "start" with the marks at zero? Once you torque the bolts the timing is set. Maybe Bobby needs to edit the manual a little; and like I need to read it a little closer 

Paul

The manual is going to be written from the initial installation perspective and I'd expect any advance/retard to be done after the install, although if the installer knew what they were doing then there's no reason it couldn't be done at the same time, but I wouldn't.

Well I think lots of builds are put together with an advance gear at installation; why not with the belt drive? I guess it's nice to have the ability to adjust the timing without the need to buy additional parts if the need arises. I just don't see changing cam timing, I say make a proper cam choice up front.

Paul

[Bakon]

The belt broke. The set up was used for racing, thus the timing was important function for the user. Belt was replaced, but not the damaged parts or time to fix. Either way, he no longer uses it. The shop they race from still likes Woods cams, just not this set up.

[Faast Ed]

Rubber don't like heat. This must be a 1/4 mile application only and not for a cruiser.

[FSG]

The belt broke. The set up was used for racing, thus the timing was important function for the user.......

How many passes had the belt made?  Did they not consider changing it after 'n passes?

[PC_Hater]

In 2004 or so I did make a suggestion to Andrews that they should do a gear-drive inner setup with the existing (now old-style!) morse chain setup.
That way you only have to check the outer chain tensioners which is easy.
Their reply was - interesting suggestion, and I think something about problems with max cam lobe height. Look at Sir Garfields drawings, high lift cams would probably hit each other! Yes the cams would have to be ground to cope with one running 'backwards' but Andrews know how to do things like that.

As for belts, well, done right they work. Ducati, Moto Morini, your car et al use them. From what I know of Woods they will be using the belt to drive high lift cams at high revs with high spring pressures and thus high forces = a step too far for the belt!