Belt Issues

Hi all, I have a 1/4 hp motor powering my C&P 8x12. It does so flawlessly when the rollers aren’t in the saddle. However, once I put the rollers on and ink up, the press gets slower and slower, until the belt falls off. I use a 4” wide leather belt. What are the causes of this?

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Without the rollers in place, pull the saddles out against the spring tension. It took you a bit of effort/work to do that. That is the same work you are requiring the motor to do when the rollers are in place.
Too much work for that small motor. 1/2 hp is appropriate for the 8 x 12.

The Gentleman I purchased it from had run it with the 1/4 since he purchased it in 1970. I’ll try a 1/2 hp anyway and see if it fixes my issue. Thanks.

If it runs slower and slower then the belt is slipping.
First thing I would check is to see if there is any oil, etc. on the belt and pulleys.
Then I would check belt tension.
And finally I would check to see if anything has shifted as far as alignment goes. Flat belts can tolerate small amounts of misalignment, depending on construction of pullies and rpms involved.

A few little extra tips,( possibly) on top of the good info, as above.>>>4 inch wide belt would seem to be rather wide, compared to say Vertical Meihle, at 2/3 horsepower pushing 2/3/4 hundred pounds of metal up and down!!!>>>Assuming you are Not running with with a purpose made, Endless Belt>>> and therfore, using the laced together style (with crocodile teeth and Metal, Nylon or Hide Pins) have the pin(s) worn making the belt run slightly less than parallel???>>>Next possibility, has been well posted recently, flat belt operation usually requires at least one pulley, DRIVING or DRIVEN to have relatively small “convex” configuration, to keep the belt running ON. Often when the machine has been, *aftermarket* motorised>>>system for true running gets over looked??If/When the machine is equipped with Belt shifter across fixed and free pulleys No Problem the shifter keeps the belt running ON??>>>Often when machines are motorised later, the easy option is to drive the BIG flywheel (which was not intended for such) with a tiny drive pulley on the motor. >>>for speed requirements of course, consequently the wrap around on the motor, (driving) pulley, can be as little as 30%>>>Have A look!!!>>>One quick fix, is to dust the inside of the belt run with Rosin or treat with Proprietry brand of belt treatment,>>>In essence TAR STICK encased in cardboard tube, for application!! SAFELY>>>Effective, Messy, and only quick fix.>>>But May prove Or Disprove other related problems, by elimination.???

I’m not a belt expert however I would allow 1” of belt width per HP. A 4” wide belt is too wide and will have a lot less tension, as mentioned above. I recall someone lined their leather belt with foam and it ran great. Time to experiment.


I too am not a leather belt expert, but I do not agree with your thumb rule. A `1/2” to 3/4” flat belt to match a motor of similar hp would not be appropriate. The width of the belt does not decrease the tension. The flat belt needs a broad surface to work on the flat drive and driven pulleys.
My 10 x 15 has a belt of about 3” and is driven with a 3/4 hp motor.

Thanks everyone for your advice. First, I gave some wrong information. The motor is 1/3 hp, not 1/4.
I have some neatsfoot oil I use for other projects. I got some clean rags and worked the oil into the belt, attempting to coat the inside surface evenly. After I felt the belt was well coated, I started and stopped the press multiple times and ran a couple hours with ink and rollers and the belt stayed on and ran at a brisk pace.