Shredding TC sprockets

[NJOHC]

Hey guys,
I have a manco dingo with a 7hp Subaru engine on it. The only things I've done to it are advance the timing and put on an aftermarket air filter and header. I am using a 30 series tc with a 9t sprocket and 60t axle sprocket. It revs to 4500RPM and I was clocked in at 45mph so its fast enough with just enough torque to get me through all the sugar sand where I ride. The problem is that Im going through tc sprockets like theres no tomorrow. I couldnt tell you how much HP the engine is making now, but between that and my gear ratio the sprockets wont last. Does anybody have any recomendations? Do they make any heavy duty sprockets to fit this?

 

[anderkart]

Have you ever tried replacing both sprockets and the chain at the same time? If the chain and rear sprocket are all wore out that little 9 tooth tc gear would be expected to wear much faster.

You might also double check your chain alignment and confirm that this gears pitch matches your chain/rear sprocket size.

I'm not sure what brand gears are the best quality but you could probably google the term: "9 tooth gear" and then add what pitch chain your running and also include the gears bore/shaft size (probably 3/4") to find serveral diferent brands for sale online.

 

[residentg]

sand is not good for chains and sprockets. Use a "clean" chain lube like bel-ray superclean, dirt does not stick to it like oil based lubes.

http://www.rockymountainatv.com/pro...Title=Chemicals&webCatId=23&prodFamilyId=4288

 

[NJOHC]

Ok thanks guys. Thats the same exact kind of chain lube/cleaner I use btw.

 

[frederic]

A new chain on a new sprocket rides practically on the root diameter of the tooth spaces, riding up on the tooth to the point that the chain pitch lies on the pitch diameter of the sprocket.

As the chain wears, it rides higher on the tooth because the sprocket pitch remains unchanged while the chain pitch elongates, defining a new pitch diameter on the sprocket. The longer a worn chain is used, the more wear occurs at the larger pitch diameter making wear pockets. Under load the chain rises up to the point that all rollers (actually every other roller) bear on the false pitch diameter.

A new chain, under load, rolls into the wear pocket of the driven sprocket and because this is for a chain of larger pitch, is unable to enter the sprocket on the slack side because it cannot reach the next tooth. In severely worn sprockets there is even a visible hook at the top of the wear pattern that prevents engagement. However, the wear pockets at a larger pitch diameter are what causes a new chain to skip on worn sprocket. No manner of filing or Dremel tool can fix this unless all teeth are uniformly reshaped, something that is both impractical and worthless because the case hardening of the sprocket is usually worn through if you can see misshapen teeth.

Interestingly there is a difference between driven and driving sprockets, something that is less apparent because chainrings (driving sprockets) are seldom changed. A worn chain will not engage a new driving sprocket although it will readily accept a new chain, just the converse of driven sprockets that we must replace when installing a new chain. This occurs because under load the chain rides on the base circle of the sprocket where the pitch is correct but the chain's pitch is too long and cannot engage the incoming tooth. Because most people use a new chain when installing a new drive sprocket, this seldom comes to light.

 

[TOO FAST]

Frederic, why don't you just write a book, we could all learn more than we ever thought
we didn't know. "Chainrings", I didn't know there was even a term for this. What the
heck do you think about when you're not working on mechanical things?
Thanks for the info, I always enjoy your posts!

 

[frederic]

Thank you for the idea but I have no time to write a book. I can barely document my projects on my website in a timely fashion. I'm about 10 projects behind lol.

I'm just fascinated by electronics, mechanical things, music, machinery, and so forth. Always have been. I thirst for knowledge and am always feeding that thirst but can never keep up.

"I wonder what would happen if I do this?" BOOM!

I vaguely remember a brief interest in dismantling and reassembling watches as that was the one and only mechanical thing my father could do very well, and had a full set of specialized tools for. I could ask him to refresh my memory but I think I dissected and reassembled my first pocket watch at age four with minimal help from him. I still have it too, and it still keeps time.

I don't know, it's just how my brain is wired. What is neat is each night I sleep since about a mont before I started buliding my son's kart, I dream about the kart and in my sleep I'm actually measuring, engineering, and designing the bits necessary to make it whole.

The difficult part is remembering any of it when I wake up ;-)

 

[NJOHC]

Wow! Thank you very much. Ill replace everything and check again to make sure everything is aligned one last time and see how it lasts. Thanks again,