Flat belt to V Belt switch

I’m running a C&P 10x15 with a motor attached to a flat belt. The motor pulley is broken and I’d like to switch to a V belt pulley system because they seem to be more readily available. I’d love any recommendations, but mostly need to know what length of belt to get.

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Are you going to be driving a large pulley on the right end of the crankshaft or driving the flywheel on the left end? If the latter you can run the V-belt on the flywheel and a V-belt pulley on the motor shaft. In that case (or the other case of running to the large flat-belt pulley) with the motor mounted where you plan to have it, and a long tape measure or a piece of non-stretch cord, measure the total distance around and between both the motor pulley and the driven — measuring the path of the belt. That will be the circumference of the belt. Many auto parts stores or hardware stores will have a belt long enough, but you might have to resort to a farm equipment place, and you may need to move the motor closer to get the belt short enough for a readily-available size. Start by getting the smallest motor pulley you can find for the slowest press speed.


Ramblings from the U.K.! Flat belt to *V* belt and Vice versa, little bit of a minefield.
From the top, (generally) in flat belt form, either the driven pulley or the driving pulley has a *Convex* contour factored in to ensure the belt Runs On,

When reverting to *V* belt DRIVING pulley, and the DRIVEN pulley has a convex contour it frequently becomes necessary to provide Belt guides on the approach of the belt to the Driven Pulley..

Rule of thumb for the length required, initially, either wrap expanding steel tape around the existing configuration (assuming the driving pulley is still fit)! quite happy to wrap around INWARDS? measure Metric or Imperial. or plastic strapping tape etc

Assuming and hoping that fairly close you have Power Transmission specialist handy, take your basic measurement(s) to them, the efficient Factors will have device for measuring lengths of Patterns however simple, convert and allow for wrap around, (flat belts are measured inner face only) *V* belts are slightly different to allow for the contact of the V whether *A* *B* or *C* section.
The same company should be able to offer virtually any length in 1” increments.

With luck and a fair wind the same company (i.e.Power Transmission specialists) should be able to offer Slave Pulleys, to fit any motor shaft size Metric or imperial, and offer adaptor pulleys, to accomodate a massive range of secondary pulleys in close ascending increments, *A* *B* *C* section etc, including single, double, or triple belt capabilities.

Once the motor output shaft is equipped with the slave, any amount of alternatives are possible. via the *Taper Lock* system = One Allen Key required.

Hopefully there is some simple means of belt adjustment, as well.

Don’t give up on the flat leather belt. Nothing beats the sight and sound of that metal belt joint going over the drive wheel. I replaced my daughter’s 10 x 15 C&P motor with a simple solution. Tractor Supply carries the proper 110 volt single phase “Farm rated” motor, bearings, and pillow blocks for the new drive shaft. I had to go to McMaster Carr to get the v-belt step pulleys and the drive shaft to match the farm bearings. All you need is a friend with a wood lathe to turn the new wood flat belt pulley. I had to ask Dave Peat, (who else would know this spec.) to find out the wood pulley had a 1/16” crown over a 4 inch width. A couple boards, a few bolts and a 1/2” v-belt and she had a working press she could control the speed of. I did have to experiment and change the pull sizes to get the right operating range. The first test ran at 32 printing cycles per minute and was very scary to watch.

image: new_motor.JPG


image: motor_to_pully.JPG


That looks really nice, moorewoodtype! I’m not opposed to keeping the flat belt system, but I need to get back to work soon and it would take some time to find the right pulley for the flat belt.

Thanks for the advice, all! I plan to keep the setup that’s already in place with the flat belt - adding a v-belt pulley to the motor shaft and running it on a large right-side pulley. I was able to find a v-belt pulley with the right dimensions and a belt that should fit based on measurements. I’ll post back when I’m able to get it running again.


You can still buy flat belt pulleys for your motor, new, from these folks:


There is a distinct difference in drive power between a V-belt and a flat belt. A flat belt is driven on the belt’s inner face; the V-belt is driven on its two vee sides. When operating, the Vee sides bulge thus gripping the corresponding V of the pulley. The upper surface and the lower surface are not designed to drive. Those using such set-up must notice the lower edge of the belt soon cracking after installation. Will a V-belt do the job? Yes. Sort of. So will a shoe lace. But putting aside the ‘wander’ of the belt on the flat surface of the press wheel,(thus neccesitating a ‘tape-groove’), power loss will be substantial. Those weak little quarter-horse motors many use to propel their press suffer enough without adding the stress of inadequate belting, and the larger motor’s slippage induces excessive heat into the belt thus hastening its wear. The above described Vee/pulley configuration is an excellent suggestion; or simply repair your existing drive pulley. Save a lot of headache.
I am astonished when reading of the mickey-mouse ‘fixes’ touted on this site. from the taped rails to the taped trucks, all are less than even stop-gap measures and do nothing to produce fine, consistant presswork. Look at it this way: would you hurtle along the expressway in a car equipped with bald tires,loose bearings, and the windshield held in place with masking tape? Would you mix bias with radial tires? Think it through. Treat your press with the respect an expensive piece of machinery deserves. Printing is far more than placing ink mark on substrate. Or is the ‘dabbler’ now ruling the tympan?

Keelan - I came across that site yesterday but they didn’t seem to have the size I need to replace my current pulley. I’ll check it out again in case I missed something in the first look.

Forme - I’d love to be able to keep the setup I have but I’m having trouble find the parts I’d need. I can’t necessarily tell from your comment, but are you suggesting that if I’m going with a v belt pulley system to replace the large flat belt pulley on the right side of the press with a large v belt pulley? It seems like that would fix the issues you mention. Or are you saying that you think a flat belt system is the only way to go?

You are correct: a V-belt functions most efficiently when both pulleys are vee type, and apopting such to your press is certainly an option. The flat belts are of earlier design - long before the V design came into being - but for their time proved efficient at transmitting power. However, cost of belting, size of crowned pulleys, slipp-age, etc., plus development of more efficient electrical motors saw the V-belt reign supreme. Interestingly, a combination of flat/V belt design is now found on most automotive engines; the drive and guide pulleys designed to keep things on track. But it must be noted those belts develop ‘allowable’ cracking on the drive surface soon after installation simply because of combining the V and flat design. It’s mainly the reinforced outer weave that holds the belt together. Of course the belt also operates at far greater stress and heat than does a belt on a C&P. Still, the principles hold. :o)


I don’t think websites are their strong suit!

Give ‘em a call — they will a pulley to suit your dimensions. They work with vintage machinery people all the time, and will he happy to help you.