I recently purchased a pricy zero-steer riding lawnmower from Troy-Bilt, a Mustang with a 50-inch deck. The design is such that there are two independent hydrostatic drives to each of the rear wheels, enabling the zero-steer capability.
After approximately seven hours of use, I started to lose torque to one of the wheels. Concerned, I jacked up the mower, crawled under it, and found that the drive belt had a twist in it. The drive belts on riding mowers are simply V-belts routed around a series of pulleys. One belt supplies power to the drive wheels and another supplies power to the mower deck. Since the machine was assembled by employees at the store where I bought it, I figured this was just an oversight. I corrected the belt and was back on my way.
It didn't take long for the condition to repeat itself. With the belt corrected, I feared that one of the expensive hydrostatic drives had gone bad. It was severe enough that I would have to have the unit repaired. This did not sit well.
I decided to try fixing it myself before I went through all the time and expense to return the unit for repair. I went online to see if there were any threads referring to hydrostatic drive slippage on riding mowers. There were some that talked about the oil getting low and causing the problem. I then checked my manual to find that my drives were sealed, so there would be no oil leak, and they wouldn’t need to be topped off. I then did some testing of the drive system on a steep hill to ensure that it was only the one drive that was having a problem. I found that the other side was also having a problem, but it was not as bad as the initial side causing the issue. That was actually good news. I couldn't imagine that both independent drives would go bad at the same time and after only seven hours of use.
Since I have a car lift, I lifted the mower up in order to get a better look at the drive belt system. I was getting the feeling that it was the culprit. Since the drive belt is routed from the engine pulley to one side drive and then the other, it is possible that if it were slipping, then the side closest to the engine drive pulley would slip the least and the conditions that I was witnessing could be explained.
When I looked at the drive belt again, it was once again twisted. No blaming it on the store employees this time. I then noticed that the tensioner arm sat very close to a bolt head that was underneath the engine securing the engine to the frame. I manually articulated the tensioner and found that the tensioner arm could hit the bolt head, which would cause a momentary loss of tension on the drive belt, allowing the belt to twist and lose its tractive power! What a huge blunder!
It was a miracle that I found a button head bolt exactly the same size in my shop to replace the standard hex head. This way, there would be nothing for the tensioner arm to hang up on. I also radiused the tensioner arm with a grinder so that there were no sharp edges to catch on anything else. Finally, I got a new belt, one that was a little bit shorter than the original, to help pull the tensioner away from the trouble area and give more tension on the belt.
After spending several hours of my time fixing something that shouldn't need to be fixed, I can say that the mower is now better than new.
This entry was submitted by Chris Clouser and edited by Rob Spiegel.
Tell us your experiences with Monkey-designed products. Send stories to Rob Spiegel for Made by Monkeys.
I bought a cheap elliptical / exercise bicycle. I didn't know if it would get much use. And if it did, then I could justify a more expensive unit. It quickly developed a clunk in the pedals. I disassembled the covers to inspect the drive, expecting to find the bearings were failing. The belt had a fixed tensioner, not spring loaded - the pedaling resistance was adjusted by a drum brake unit. I don't know how they assembled the tensioner - the belt was ridiculously tight. I had to struggle to unbolt and remove the tensioner - it was at the end of the adjustment for 'looseness'. After several minutes of pondering I re-routed the belt and re-installed the tensioner. The belt is now snug vs. piano string tight. And the clunk is gone.
Chris - I admire your tenacity in troubleshooting the problem. It seems that you should have been the design engineer on this mower. It also makes me wonder how much testing is done during the development stages for these types of products. It seems like this problem should have been recognized during product development.
Good point, Nancy. This blog could just as easily be a Sherlock Ohms entry, since Chris went through the process of identifying the problem and coming up with a long-term fix.
Looks like another "Fixed by Clever Humans" column. I especially like how the author changed various dimensions, like distance from tensioner arm to bolt head and belt length. I agree with Nancy, he should have been the design engineer for this product.
I have found numerous opportunities to choose better bolts, knobs, transistors, resistors, capacitors, etc. on various pieces of equipment in my days. And certainly, in many cases, I could have written a better manual after spending only a few hours with a product. I could certainly spell better than they did.
We shouldn't expect perfection with most devices. They only had to meet spec for marketing. He was lucky to have a lift and to see the problem. I wonder how many of these were sold off on Craig's List to some unwary soul who spent a fortune on repairs never to be satisfied?
Yes, Ann, another "Fixed by Clever Humans" column. I do wonder, though -- did the manufacturer bother to test this design? From what I'm reading here, the design flaw could have happened on any or all of its mowers. Shouldn't they have picked that up in test?
For an item this expensive with only 7 hours of use, it surely would have been covered under warranty to troubleshoot the bad design. There may have been a technical bulletin explaining the issue that the repair tech could have reviewed.
Problem with a warranty claim, is you will only get the product repaired to the faulty design standard.
There are many times when I regard what I buy as not so much a product, more a set of parts from which to assemble something better.
I have a self-propelled Troy-Bilt walk-behind mower. In 7 years of ownership, I had to replace the rear drive wheels, the front axle, front axle support bushings (three times!), rear drive transmission, and four drive belts. The paint flaked off the inside of the deck years ago. To be fair, when it is working, it works well, but I have invested 50% of the purchase price to keep it running for the last 7 years! More evidence that the monkeys work for Troy-Bilt (and their parent, MTD)! I will NEVER buy a Troy-Bilt product again!
It seems like all the "Fixed by Clever Humans"--oops, I mean, "Made by Monkeys"--columns are about products that were never tested, or at least, never tested in any way that's relevant to their actual use.
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