Dementions Or better Picture of Large Paramount Sprocket

[ColsonTwinbar]

So I have access to a water jet machine at my school and I've wanted to make a replica of the very large Schwinn paramount sprocket. Does anyone know the dimentions or have large picture or scan or it?
-Nolan

[RMS37]

I'll go out on a limb and say I may be able to help. There are reasonable pictures on the internet which could be projected to create an accurate drawing. The teeth will have the same profile as a standard 1" pitch sprocket and the pitch circle will be in even inches. counting the teeth and rotating them around the pitch circle should give a working sprocket. The original sprocket web is thicker than the teeth so to replicate that you will need to cut the sprocket from a plate the correct thickness and then turn the teeth down to fit 3/16" chain.

I'll see what I can generate in the next week.

[Strings-n-Spokes]

This thing? What a cool idea!

[ColsonTwinbar]

thanks phil,

and that picture might work, I would like to get a picture with a full wheel in it so i can compare and get the size.

[RMS37]

I started drafting the sprocket; it has 57 teeth (56 remaining considering the one missing tooth) which sets the chain pitch circle diameter and thus the outside diameter of the chain ring. I laid out the circular cutouts from the photo so the only remaining questions are the thickness of the chainring plate and the exact bolt circle diameter and size of the crank arm mounting holes. A standard Paramount crank has a larger diameter 3 pin mounting circle and this unit appears to have a 5 pin mount similar to an old BSA track crank.

I need to do a few more measurements to calculate the tooth profile and I will post a picture with dimensions in the next couple of days.

[ColsonTwinbar]

cool, I was able to make the general circle pattern in about 10 minutes so i just need the diameter and number of teeth.

[RMS37]

Here is the drawing I built from the photograph of the chain ring, once the number of teeth is determined the diameter of the sprocket is fixed, the dimension I give is a preliminary measurement and should be adjusted and checked further to be certain the chain will mesh properly with the teeth. A miscalculation of 1/100 of an inch between contact points for the chain on adjacent teeth will multiply by roughly 30 over the length of the chain to sprocket contact (about a third of an inch.) I’ll do some more precise measurements next week to make sure the sprocket will be functional although a 57 tooth inch pitch sprocket could probably be considered dysfunctional by definition.

[ColsonTwinbar]

Nice work! What program is that done in? I think a catia file is preferred but Illustrator and Rhino cad files work too.
-Nolan

[RMS37]

It was drafted in Autodesk's AutoCAD which I would assume can be imported to most computer aided machining programs where the raw data could be used to produce machining instructions and paths; not something I have done though.

After I get the tooth pitch and profile fine-tuned you are welcome to a copy of the ACAD dwg file to see if you can use it to produce the chainring.