Timing is everything

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Dances with Shrapnel

Dances with Shrapnel

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Timing is everything


Engine is 500cc ultra short stroke.

One off custom barrels are from billet aluminum.

Small idlers are custom pinions fitted with roller bearings.

Cam gear is cut down from Norton intermediate timing gear.

Three allen bolts on cam gear are for fine adjustment to cam timing.

Design, engineering and fabrication by Herb Becker.
 
Dances with Shrapnel said:
Timing is everything


Engine is 500cc ultra short stroke.

One off custom barrels are from billet aluminum.

Small idlers are Norton crankshaft timing pinions fitted with roller bearings.

Cam gear is cut down from Norton intermediate timing gear.

Three allen bolts on cam gear are for fine adjustment to cam timing.

Design, engineering and fabrication by Herb Becker.
Click to expand...

I looks like one idler gear is a crankshaft pinion. The other idler is something else. I know it can't be a timing pinion because two timing pinions will not fit in that application. They will clash as they are too small. Jim
 
Hello Jim.

My bad.

Version 1 used a single Norton crankshaft timing gear whereas version 2 shown above uses two idlers of unknown origin and size; at least one is larger than the Norton crankshaft timing gear for the reasons you cited.

I guess I did not keep up with the changes in technology. :oops:

I have changed the description above for the record.

Makes for a different sound when running.
 
I used one with a single crank pinion for a while. I ran it for about a month and then heard a tapping noise from the timing chest. When I pulled the cover I found the pinion was missing one tooth and the next tooth was cracked. Lucky I shut it off when I did. Jim
 
You really need two idlers unless you can safely fit a large enough one near mid point between the cam and large idler and that will not work in this application for obvious reasons.

Where we have been having trouble is in keeping the gear tight to the cam and crankshaft pinion tight to the crankshaft. It may be inadequate torque and/or inadequate key fit or a combination of each. Considering thread locking compound. Any thoughts here Jim?

Most anytime the timing chest is open is not a good sign. In this instance the crankshaft pinion split at the keyway. A couple of teeth (and the key) went missing. Hopefully there was no valve clash as I did not sense any carnage while running it.

The reason we migrated to a gear drive was the chain and slipper adjuster were not up to the task. At one point we were spinning the motor regularly well past 10,000 rpm with an N480 cam and it was brutal and predicatably short lived. We have since tamed it down with minimal loss of top end and improvements in mid range.
 
Dances with Shrapnel said:
You really need two idlers unless you can safely fit a large enough one near mid point between the cam and large idler and that will not work in this application for obvious reasons.

Where we have been having trouble is in keeping the gear tight to the cam and crankshaft pinion tight to the crankshaft. It may be inadequate torque and/or inadequate key fit or a combination of each. Considering thread locking compound. Any thoughts here Jim?

Most anytime the timing chest is open is not a good sign. In this instance the crankshaft pinion split at the keyway. A couple of teeth (and the key) went missing. Hopefully there was no valve clash as I did not sense any carnage while running it.

The reason we migrated to a gear drive was the chain and slipper adjuster were not up to the task. At one point we were spinning the motor regularly well past 10,000 rpm with an N480 cam and it was brutal and predicatably short lived. We have since tamed it down with minimal loss of top end and improvements in mid range.
Click to expand...

I agree that the chain is the week link when abused with a big cam and high RPM. And I hate the amount of metal that goes into the oil from chain and guide wear. However what I have found is the chain provides a lot of cushioning effect for the gears.
When I have done away with the chain, the gears take a hell of a beating and damaged or missing teeth between the standard crank pinion and intermediate gear have been a problem even with a mild cam on the street. Replacing all of the gears with gears made of a better material has held up pretty well but it gets a bit pricey. Jim
 
I've looked into belts for this to find various types/teeth forms need to be about 3/8" wide to be strong enough which makes the pulley width an issue to fit. Tension adjustment also needs solved unless could source a belt T count for pulley ratio diameters needed that slips loose enough on/off w/o any need of tensioner.
 
comnoz said:
I agree that the chain is the week link when abused with a big cam and high RPM. And I hate the amount of metal that goes into the oil from chain and guide wear. However what I have found is the chain provides a lot of cushioning effect for the gears.
When I have done away with the chain, the gears take a hell of a beating and damaged or missing teeth between the standard crank pinion and intermediate gear have been a problem even with a mild cam on the street. Replacing all of the gears with gears made of a better material has held up pretty well but it gets a bit pricey. Jim
Click to expand...

With the dual idler set up, this is the first for any gear giving grief. Maybe we have been lucky. The double idler provides substantial stiffness that a single idler cannot provide.

I am thinking the lash due to loose key fit on the cam may exasperate the hammering in the cam drive. The loose key may also be contributing to the cam nut coming loose.

@Jim: do you use any locking compound on the camshaft nut or crankshaft nut? How do you get them tight. I never had this problem before.
 
Something amiss as wood ruff key not supposed to take the torque loads, just align the sprocket so tapper fit binds up good.

Best Chevy cam drives use dual idlers and a special delight to see it live in a Norton.
Timing is everything
 
one of the BIG issues to overcome is the harmonics of the camshaft in a 360 degree twin cylinder verses a V8 engine


hobot said:
Something amiss as wood ruff key not supposed to take the torque loads, just align the sprocket so tapper fit binds up good.

Best Chevy cam drives use dual idlers and a special delight to see it live in a Norton.
Timing is everything
Click to expand...
 
Dances with Shrapnel said:
comnoz said:
I agree that the chain is the week link when abused with a big cam and high RPM. And I hate the amount of metal that goes into the oil from chain and guide wear. However what I have found is the chain provides a lot of cushioning effect for the gears.
When I have done away with the chain, the gears take a hell of a beating and damaged or missing teeth between the standard crank pinion and intermediate gear have been a problem even with a mild cam on the street. Replacing all of the gears with gears made of a better material has held up pretty well but it gets a bit pricey. Jim
Click to expand...

With the dual idler set up, this is the first for any gear giving grief. Maybe we have been lucky. The double idler provides substantial stiffness that a single idler cannot provide.

I am thinking the lash due to loose key fit on the cam may exasperate the hammering in the cam drive. The loose key may also be contributing to the cam nut coming loose.

@Jim: do you use any locking compound on the camshaft nut or crankshaft nut? How do you get them tight. I never had this problem before.
Click to expand...

I suspect a gear drive is going to see less problems from harmonics at high speeds. The biggest problems I have experienced with my prototypes have been in the 3 to 4 thousand rpm ranges. I have a single idler gear drive with around 20k on it now. The idler consists of three stacked, spring loaded gears and spring fatigue has been an issue.

I recently sent some drawings to my tool grinder for a gear cutter with some different angles that may help with some of the gear wear I have been seeing with a gear drive like yours. I plan on some new prototypes as soon as I get caught up a bit.

I do use locktie on the cam nut. I drill holes in the gear to hold it with a pin spanner for torquing. So far I haven't had keyway problems but I can see how it could be a problem.

I have a prototype belt drive partially done also. Kind of scared to try it out. I have seen oil temps in the timing chest that would likely destroy a belt- but I usually only see oil temps that high on the dyno. Jim
 
TLK type hubs have incredible clamping force up to where the diameter of the shaft gets sqeezed making it a pain to get it off again. This was on screw compressors with say 75mm shaft ends.
Problem on the Norton is the restricted room for it.
How do other designs with a single intermediate hold, say like the BSA A10/A65? Is the larger diameter intermediate the key to success? Do not recall any issues with this setup. Bennie.

Timing is everything
 
The taperlock type hubs work well. We used a couple of them in the blower drive on the Eccosse. I don't know if there is room in a Norton chaincase or not.

The biggest problem with the Norton with gear drives and the stock pinion is the fact that the stock pinion is very poor quality gear metal [or hardening]. They shatter like glass with little torque.

I think a good gear drive can be done but it will involve replacing all the gears with better quality items. Jim
 
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