Underdrive pulley and adjustable cam gears....

[krymis]

need help making a set of adjustable cam gears for the same project as the tb. I need to make an underdrive pulley and I need adjustable cam gears. I have factory ones at my disposal for measuring, but how to design and get code for them from bobcad V21......

[isaiahdakotaarm]

are you just going to duplicate the originals or are you going to create new designs to better utilize efficiencies?

in the case that you were going to design new ones, decide on the proper gear tooth arrangement, pitch angle, all that fun stuff, and bcc v21 will generate the gear for you, its a tool under Other>Gear.

as for the pulley, that should be fairly simple, my suggestion would be a revolved surface, just draw the basic outline of the pulley in proper relationship to the origin, then do a revolved surface about the "desired" axis.

[krymis]

the gears have 50 valleys. What measurements do I need? I just want the stock set and to be able to adjust them +/-12 degrees. Here are the AEM cam gears i wanted to replicate.

[isaiahdakotaarm]

I'm not a gear guy, i have just had to deal with them a bit, call a gear manufacturer, they will be able to help you. you can try Grob inc. they are a custom rolled form shop, they have made some gears for me in the past and are usually quite helpful.

[tjones]

The trouble is those are automotive timing gear more like a grooved pully and not a true gear with a formed gear tooth.

Most of those are just a radial groove. A ball endmill in a 4th axis could handle some of them while others require a tapered endmill.

In this case either send it directly to a manufacturer or get the dimension and do a detailed print or solid.

[krymis]

being that my daily job is a college professor I sent it over to our machine division to have it measured and it will be back Monday. I found that it is called a synchronous belt gear. It seems to be a 3/16 ball endmill on a 4th axis operation.

[isaiahdakotaarm]

alright, then it should be fairly simple to manufacture, just remember to compensate for ANY backlash in the 4th axis when producing the pulley otherwise the teeth end up out of time, you develop a strange wear pattern in the belt, and eventually everything breaks. If you have access to a Wire feed EDM i would suggest using it to manufacture the pulley, Thats how i have made spline shafts and such in the past.

[tjones]

Glad to see someone else does splines on a wire.


We make spines (gear,broaches, guages) here quite often on wire machines. However they are a bit expensive to do that way. I even have made some of those drive belt pulleys on one. But we have a really good 4th axis on our mill and it does a very good job of parts like this. (hydraulic lock)

Originally Posted by krymis

being that my daily job is a college professor I sent it over to our machine division to have it measured and it will be back Monday. I found that it is called a synchronous belt gear. It seems to be a 3/16 ball endmill on a 4th axis operation.

Make sure your tolerances don't vary more than +-.001. Perpendicularity, Runout and T.I.R. You don't want that Timing Belt coming off. I'm not a gear designer but have made gears and pulleys many times on High Speed Shapers, Hobbers, and CNC Hobbers.

The slightest wabble at 5,000 RPM and that belt is gone.

[tjones]

I helped install a rotary scale on a Jungner Grinder once for grinding spline teeth. They had .0002 tolerance on their parts and the indexing accuracy was unreal. The rotary scale was the only way to get the required tolerance.

Of course that company makes things for race cars and Boeing aircraft.