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Step 17Installing new chain tensioner.
Chain Tensioner.
One of the biggest problems I had with the old mower was the rear axle chain setup. The chain repeatedly either came loose or snapped. This might have been due to the old chain being a #35 size, which is a bit small. I elected to upgrade the chain to a #40 size which meant new sprockets. At the same time I also installed a new RAGB transmission. The old one had always had a lot of play and slop in the gears. This never caused a problem. But I decided to install a duplicate I found on Ebay a year ago. The old one will serve as a spare.
The key to having the rear chain not fall off is the correct combination of proper alignment and tension. All chains will stretch as they wear. Thus the best setup involves a spring-loaded idler. In this case I used a idler sprocket. The fatter chain meant that it would be hitting the top of the transmission mount. The old #35 barely cleared it. Thus I had to cut out one side of the mount and weld a new piece behind where that piece had been. Thus the mount was staggered back enough to allow the chain to clear.
A great deal of time was spent ensuring that all 3 sprockets were absolutely aligned. This is done with a flat steel ruler. Since the tranny is more or less not adjustable the idler and rear axle sprocket both needed to be aligned with the tranny sprocket. Lay the ruler flat over all 3 sprocket surfaces in such a way as that all of the gear's sides are totally flat- as in the ruler lays flat across all 3. Gently tap the sprockets until this happens. This needs to be absolutely perfect so spend some time.
The tensioner I use is one I made 2 years ago. I modified it to use the larger idler sprocket. I also relocated the tension spring in such a way as so it pulls directly up. Previously the spring was pulling slightly forward, which I think might have caused the idler to jump off the chain. The tensioner itself rides in a slotted piece of square tubing. A bolt runs through the slot and thus allows the entire tensioner to float up and down. The spring keeps the tensioner against the chain. As such even if the chain stretches, the tensioner will always apply the same amount of pressure.
One of the biggest problems I had with the old mower was the rear axle chain setup. The chain repeatedly either came loose or snapped. This might have been due to the old chain being a #35 size, which is a bit small. I elected to upgrade the chain to a #40 size which meant new sprockets. At the same time I also installed a new RAGB transmission. The old one had always had a lot of play and slop in the gears. This never caused a problem. But I decided to install a duplicate I found on Ebay a year ago. The old one will serve as a spare.
The key to having the rear chain not fall off is the correct combination of proper alignment and tension. All chains will stretch as they wear. Thus the best setup involves a spring-loaded idler. In this case I used a idler sprocket. The fatter chain meant that it would be hitting the top of the transmission mount. The old #35 barely cleared it. Thus I had to cut out one side of the mount and weld a new piece behind where that piece had been. Thus the mount was staggered back enough to allow the chain to clear.
A great deal of time was spent ensuring that all 3 sprockets were absolutely aligned. This is done with a flat steel ruler. Since the tranny is more or less not adjustable the idler and rear axle sprocket both needed to be aligned with the tranny sprocket. Lay the ruler flat over all 3 sprocket surfaces in such a way as that all of the gear's sides are totally flat- as in the ruler lays flat across all 3. Gently tap the sprockets until this happens. This needs to be absolutely perfect so spend some time.
The tensioner I use is one I made 2 years ago. I modified it to use the larger idler sprocket. I also relocated the tension spring in such a way as so it pulls directly up. Previously the spring was pulling slightly forward, which I think might have caused the idler to jump off the chain. The tensioner itself rides in a slotted piece of square tubing. A bolt runs through the slot and thus allows the entire tensioner to float up and down. The spring keeps the tensioner against the chain. As such even if the chain stretches, the tensioner will always apply the same amount of pressure.
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