Crofter Posted August 17, 2019 Share Posted August 17, 2019 I've been lent an old whacker plate. First time out, the belt spins off, stretched and frayed beyond use. No numbers or identifying marks on either the belt or the machine, so I measured up as best I could and bought a couple of belts cheaply off eBay. The smaller belt does fit, and the machine works, but it's pretty loose. So how much tension should there be? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 17, 2019 Share Posted August 17, 2019 Is the belt a vee belt? If so, then it needs to be pretty tight, usually about 3mm to 4mm of inward centre deflection per 100mm of belt unsupported length on the longest run. So if the longest length is around 300mm, then the inward deflection when pushed hard by your thumb in the middle of the run should be about 9mm to 12mm. Link to comment Share on other sites More sharing options...
Crofter Posted August 17, 2019 Author Share Posted August 17, 2019 Yup a vee belt. There is no way of adjusting tension, so I don't see how I could ever get a particularly tight fit, as it has to pass over the pulleys. The one that I'm using just now is such a loose fit- zero effort to force it over the pulleys- that I'm amazed it works at all! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 17, 2019 Share Posted August 17, 2019 If there's no belt adjuster, then the chances are that the tension is adjusted by spacers or shims to physically move the two pulleys apart, or possibly it may use a split pulley adjuster. The split pulley adjuster will have three or four bolts holding two halves of the pulley together, with a spacer between the two halves, that effectively changes the internal diameter of the pulley to tension the belt. If I had to guess then I'd say that the adjustment is most like made by moving one pulley away from the other somehow, as split pulley adjusters are not that common. Any chance of a photo? Link to comment Share on other sites More sharing options...
Onoff Posted August 17, 2019 Share Posted August 17, 2019 Slots? Pulley shaft on a cam? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 17, 2019 Share Posted August 17, 2019 5 minutes ago, Onoff said: Slots? Pulley shaft on a cam? My money's on a split pulley tensioner, with spacer plates between the two halves, thinking about it, as they are completely vibration resistant, so the tension would be maintained no matter what. Link to comment Share on other sites More sharing options...
Onoff Posted August 17, 2019 Share Posted August 17, 2019 1 hour ago, JSHarris said: My money's on a split pulley tensioner, with spacer plates between the two halves, thinking about it, as they are completely vibration resistant, so the tension would be maintained no matter what. Something like this then: https://stores.dhsequipmentparts.com/blog/howto-wacker-bpu3545-belt-adjustment-replacement/ 1 Link to comment Share on other sites More sharing options...
Jeremy Harris Posted August 17, 2019 Share Posted August 17, 2019 8 minutes ago, Onoff said: Something like this then: https://stores.dhsequipmentparts.com/blog/howto-wacker-bpu3545-belt-adjustment-replacement/ Spot on! Exactly what I was thinking of. Link to comment Share on other sites More sharing options...
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