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Message started by Armen on 11/22/19 at 17:48:56

Title: Cam chain mods
Post by Armen on 11/22/19 at 17:48:56

So, I'm finally getting this part back together. Have a Web cam, and the modified tensioner.
Further twiddled the tensioner by removing the ratchet and pawl, grinding off the aluminum that isn't needed anymore, drilled holes top and bottom for oil to flow in and air and oil to flow out. Cut a piece of 1/4" rod to fit inside the spring and only allow a little bit of tensioner travel.
Put a window in the cylinder so that I'll be able to see how tight the chain gets when the cylinder is at operating temperature. Figure I'll remove the cap and just push back on the chain and tensioner to see if there is a little slack.
Drilled the cam sprocket. Not much else to poke holes in around there.

Title: Re: Cam chain mods
Post by Dave on 11/23/19 at 05:21:39

Drilling the cam sprocket brings back memories of me drilling the 13mm wrench......drilling hardened steel is at the upper end of my competence level - maybe reaching my incompetence arena. I trashed 4 drill bits to lighten a 2.7 ounce wrench to 2.2 ounce! I used Cobalt drill bits and they would work until they lost the cutting edge......after sharpening the Cobalt coating was gone and they would no longer cut the hardened steel. The chrome plating was the hardest on the drill bits.

I saw a photo of the Worlds Fastest Indian, and the lightening of parts was incredible. Burt Monroe had drilled lots of holes, and the transmission gear were cut down in width......he had made everything as light as possible, and sometimes the parts were too light and failed. He was pushing the engine to the limits of lightness vs. strength.

Title: Re: Cam chain mods
Post by Armen on 11/23/19 at 05:29:51

Actually, the part that I drilled on the sprocket was not hardened. Did it with one bit.

Title: Re: Cam chain mods
Post by Armen on 11/23/19 at 05:32:00

Somewhere I have a pic of an early 70's factory Ducati with everything drilled. Crazy, amazing work.
Now you can just design parts lighter. Back then, adding lightness was the way to go.
My inspiration for this build are the racers of that era...

Title: Re: Cam chain mods
Post by Serowbot on 11/23/19 at 08:13:30

Talk about patience.. :-?
http://2.bp.blogspot.com/-IHSnTKwq5Ic/TwfVTSoEINI/AAAAAAAAAvo/7_SJVtI5VQA/s1600/drilling-do1.jpg

Title: Re: Cam chain mods
Post by Dave on 11/23/19 at 10:43:46

4157405D45505D46320 wrote:

Talk about patience.. :-?

That appears to have been done by a man who is afraid to leave the garage and go inside to spend time with his wife and family!

Title: Re: Cam chain mods
Post by Armen on 11/23/19 at 10:48:43

Worked in a bicycle shop in the early 70's. Did lots of drilling. All freehand. None as nice as that. IIRC Stronglight was a French outfit, kind of second tier to the Campagnola stuff.
What is amazing is that those chainrings were probably laid out and drilled by hand (drill press).
Thanks for sharing.

Title: Re: Cam chain mods
Post by DragBikeMike on 11/23/19 at 12:01:14

That is outstanding. The picture really shows the important details. What a useful mod.

It allows monitoring cam chain and guide wear without removing the clutch cover. You should be able to establish a threshold by installing the tensioner & guide without the cam chain. Position the tensioner at your desired threshold (18mm, 20mm, whatever you feel comfy with) and then take photos and possibly make a reference mark too. One small problem with the reference is that it does not account for guide deflection.

Another option for monitoring using your inspection port, would be some sort of ball gage. You could insert a ball attached to a heavy wire and measure/check the distance between the drive side of the chain and the slack side of the chain.

That's a really good mod you came up with Armen. My compliments.

Title: Re: Cam chain mods
Post by Armen on 11/23/19 at 14:15:01

Thanks DBM!
Now all I have to do is get it done!!!!

Title: Re: Cam chain mods
Post by ohiomoto on 11/23/19 at 15:18:23

Armen, you're crazy!!

But that's what makes all this stuff so cool!!! Looking forward to more pictures.

:)

Title: Re: Cam chain mods
Post by Armen on 11/24/19 at 05:28:14

Here are the stock and modified tensioners. I wiped off some aluminum on the body, and drilled some holes. The arm was extended when I got it. Don't need it now, but if/when I shave the cylinder, I'll need to take up more chain slack.

Title: Re: Cam chain mods
Post by DragBikeMike on 11/24/19 at 10:49:30

I think the extended arm/plunger works to your advantage by giving you more engagement with the body. It's more stabile. I also like your drilled feed hole in the top. I can see from the polish on mine that there is a lot of action between the plunger and body. Yours will have better lubrication. I think I will add the hole to mine. I also see that you put a drain hole in the bottom at the extreme end (high side of body). That's cool. I personally don't think you need the drain but I also don't see it hurting anything.

Have you tried reaching through the hole and pushing back on the chain & guide? What sort of action do you get? If you imagine that the clutch cover is in place, is it pretty evident that the plunger is retracting when you push back on the chain/guide? Is it evident when the plunger bottoms out, or does the rear guide start to deflect and make things a bit foggy to evaluate?

Title: Re: Cam chain mods
Post by DragBikeMike on 11/24/19 at 10:58:20

The 1/4" rod used as a stopper is also a nice touch. Keeps things centered up. I like it. Seems to be a bit more robust than simply inserting a couple of 7mm washers like I did. Does the action change when the stopper rod is installed? Seem just as smooth as it was without the rod? I might steal that idea too. Keep em comin buddy. ::)

But hey, all the weight you saved by turning down the aluminum body was returned in spades by installing the steel rod. Can't you do a titanium rod? For that matter, you should look into a titanium plunger. ;D

Title: Re: Cam chain mods
Post by Armen on 11/24/19 at 20:23:46

Hey DBM,
Thanks for the kind words. No binding on the plunger with the rod in the spring. I assembled it with the spring, and marked the plunger. Then I took it all off and figured out how long I'd have to make the rod to have the plunger extend as far as it had. A little cut/try/check and it's all happy.
I might make a plunger out of 7068 aluminum. And I do have a length of 1/4" Ti rod laying around...
But for now, I'm trying to get this running before I die of old age :-0

Title: Re: Cam chain mods
Post by batman on 12/10/19 at 11:24:26

Use of the stock plunger might have some advantage , if rotated 180 degrees, the flat and teeth used for the paw could be used to help lube the plunger and the spring , simply by drilling one hole as far back in the top of the body as possible , allowing the oil to fill that area and also run downhill over the paw teeth which might distribute oil to each side of the plunger . oil in the rear of the body might lube the spring(and the need for the rod) and even help dampen movement . the toothed flat and/or the hole would prevent any chance of hydraulic lock .
I don't favor adding a rod to the back of the plunger . If it's too short ,it does nothing ,If too long it will cause chain stretch ,until it is too short . How do you really determine proper length ? Doesn't the force that the chain places against the guide increase at higher speeds, and decrease at lower speeds? Allowing for the change in cylinder and head height as the motor comes up to operating temperature may not be enough . In any event I'd remove the rod and allow the plunger to be free floating .

Title: Re: Cam chain mods
Post by Armen on 12/10/19 at 14:45:38

Hey Batman,
The plunger length question is why I put the window in the cylinder. As I said, I plan to get the bike nice and hot and see how much chain slack there is. A bit of cut and try and I should be able to come up with the correct amount of plunger movement cold to end up with zero when hot.
Yes, I drilled holes in the tensioner body to allow oil in and out.

Title: Re: Cam chain mods
Post by batman on 12/10/19 at 18:03:27

Armen ,I wish you good luck ! we all need to hear how your setup works out .