SP-15 Motor Belt

Katie-SP-15 Pulley

The oscillating roller on one of our SP-15 presses began hesitating this week, out of the blue, just like the video posted in January. For that poster, it seemed the solution was a new belt. However, both the motor and belt on our press are relatively new, so I figured that might not be the solution for us. Our motor was completely replaced a couple of years ago (I blogged about it here), and the pulley now uses a V belt. I double checked the belt today and found it had worn loose and was slipping; it was also out of alignment with the drum cylinder. There are rubber shavings where the belt has worn against the pulley, maybe because it is out of alignment. We were able to get it back into alignment fairly easily, but the belt is still loose. When the new motor was installed, it was not the same shape as the old one, and had to be mounted to the base a different way. They did not put in slots so that the motor can be moved slightly to take up slack in the belt. My machine shop neighbor (how handy is that?) has told me that if he can remove the bottom of that well where the motor lives, he can drill slots for us. He thinks that he can remove this “well” by releasing a pin (see photo) on either side. Is that doable? I also figured to replace the V belt with a gear belt, which is what is in our other SP-15 which seems to have the original motor/drive system. A quicker solution might be to get a slightly smaller belt, but I would prefer a longer-term fix, if possible.

10 thoughts on “SP-15 Motor Belt

  1. Katie Harper - February 23, 2014

    Well, I have been able to make a temporary fix. Had to remove both motor and cylinder, and I decided to see if I could find a better belt. I wasn’t hopeful that I’d be able to on a Sunday. Found one at a local hardware store but it was 18″ 3L (3/8″). I suspected that the 3L was what we really needed, but didn’t think the 18″ would work. Gave it a try, and it fit perfectly, much better than the old one that was too thick and loose. I suspect that 19″ was actually too long, length perhaps making up for extra bulk? I think the guys who installed the motor were not too careful about the belt. (And yes, this somewhat imprecise installation cost us well into 4 figures…)

    Anyway, as you can see from the picture, this new belt fits more snugly and everything is running quite well, although we have yet to test it with ink on the rollers. I still think some further adjustments need to be made, but this seems to work for now.

    Thanks to all for advice!

  2. Eric Holub - February 23, 2014

    Looking at the belt shown above, there is minimal contact with the pulley, a third of the diameter at most. There should be more contact between belt and pulley, which is to say a slightly shorter belt is needed, and with small-diameter pulleys the notched belts will make such a curve more easily. It isn’t about teeth meeting teeth, just getting around a tight curve.
    If you are talking about a link-belt, they are highly recommended for another application (lathes) where installation is difficult or vibration is a problem.
    Maybe there are problems with the rollers too, but from the picture the belt should be replaced before any modifictions are made to the press.
    I have been seeing more posts about press problems where machinists as quoted completely misunderstand the mechanics of press design. Not a good omen.

  3. Lad Boyle - February 22, 2014


    Not having used an adjustable belt to run my press, i dont know if it works or not. But it should if you can get it tight. I have an old band saw that i run with an adjustable belt – it works, but i don’t remember how hard it was install and get it to work.

    The adjustable belt is relatively cheap – if you don’t have the time now to take your press apart – buy the belt and see if it works – nothing ventured, nothing gained. Maybe it will work well enough that you will be satisfied without doing more.


  4. Katie Harper - February 22, 2014

    Thanks, Lad. Your story was very helpful. We had also noted those bolts and figured they would work if the pin is not removable. This longer-term fix will have to wait til I have a larger block of time. Meanwhile, I’m going to try a bit of belt dressing and maybe order the adjustable belt as well. Will that work for short term?

  5. Lad Boyle - February 22, 2014


    A couple of years ago, I bought a SP15 with manual inking. I was able to buy the parts to retrofit the press with power inking, thanks to everyone’s friend Fritz.

    The “pin” you marked does not come out, at least I dont think so. Its a swivel for the inking system to pivet when the rollers and the carriage are returned to the start position.

    But in the picture there are bolts that hold an “L” bracket. There are similar bolts on the other side. These bolts can be removed and the pan, etc can be removed by lowering it. I did not install the motor until the pan was bolted in place. The full assembly is very heavy and hard to work with in the confined space. You should take your motor off before trying to dis-assemble. You will need to take the back panel off to be able lower the pan.

    There is a post on Vanderblog describing my process – probably some time during the summer/early fall of 2012. You should be able to search for it. [https://vandercookpress.info/vanderblog/2012/08/power-inking-for-sp-15/]

    When you reinstall, again its heavy and not an easy place to work. To do it, I lifted from the top and had my wife stack wooden blocks under the pan until i got it to the right height and then was able to replace the bolts in the L bracket, reinstall the motor, etc.

    Its doable, but not a quick easy job

    In the long run, I think you will be happier with this than continuing to replace belts

    Good Luck


  6. Katie Harper - February 22, 2014

    Unfortunately, there is no way to add or relax tension to the belt. The motor position is fixed. Our current belt is 19″; next size down is 18″. As near as I can figure, the adjustable belt we need has 14 links per 12″ so 22 links would give us 18.857, which might be just right. It’s hard to know until we try. However, the only adjustable belt in the right length and 3/8″ width is 1/2″ thick, and our pulleys are only about 5/16″ deep. So the belt will stick out and may rub against the lever shown in the photo.

    It seems like the best long-term solution is to either change the pulleys to gear-belt type, which I’m assuming can be done, since our other SP-15 has that setup. Any thoughts on this and how we’d go about it? And possibly fix the motor so it can be moved slightly to take up slack when needed. This is why the machine shop guy suggests putting slots in the base so the motor can be moved slightly to add tension in the belt when necessary. Hence the question about whether removing the side pins would allow that base to be removed. Does anyone know?

  7. Mark Herschede - February 21, 2014

    Also- this should go without saying, but you should buy more belt than you need.
    Additionally, the belt is maybe going to split to the right length, maybe not; kind of like a bicycle chain.
    One thing you may want to do is tension the motor or pulley to it’s loosest point before fitting the belt, if that is even possible. The motor mount should allow for a little play and you will want to give it the max amount, fit the belt, and then re-tension the motor so as to take up any slack/make the belt tight.
    Good luck!

  8. Mark Herschede - February 21, 2014

    The strength/durability of these adjustable belts will surprise you as well. I’ve used them in a pinch to keep from disassembling a machine (my Universal II is driven by a belt pulley system) when replacing a worn/frayed belt.

    If the pulley gap is about 3/8″, get a 3/8″ belt. Just don’t try to put a larger belt on the pulley than the gap, or you will potentially see issues.

    Mcmaster ships fast and they are usually near you at at least one location.

    Good luck.

  9. Katie Harper - February 21, 2014

    Thanks, Mark. I was unaware of adjustable belts. Great concept. When I removed the drum cylinder to measure our current belt to order a matching size in adjustable, I found the belt doesn’t really fit the V of the pulley. I think our belt is too large. I measured the width of the V on the pulleys on both the cylinder and the motor, and they seem to be 3/8″. The belt is 1/2″. I’m not sure if this makes a difference but it seems like it would. I suspect the guys who installed the new motor just went with whatever belt seemed to work. If I order a new adjustable belt, I want to be sure I’m getting the right width, depth, etc.

  10. Mark Herschede - February 21, 2014

    Get some adjustable length V belting:


    and make the belt just the right length.

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