V-belt stretch

[Braeden P]

I Always wear a helmet when driving it, don’t want to be any dumber if it crashes

 

[SLK001]

I'd be wearing a full face helmet. When you crash, your face is the first thing that's going to hit. That is, unless you like the taste of teeth.

 

[Jake M]

I got a manual lawn tractor for $80 and like any stupid kid I pulley swapped it (1:2.5 to 3:1) blew a few belts and the replacement one was 2” longer than the original one (very loose without tensioner and needs it all the way out) and after stretching 2” in a minute I had to put on a second tensioner and I got a new belt that was 2” shorter then the original belt 82” vs 84” and it won’t go on so I tried to stretch it and it wouldn’t stretch even a bit, do some belts stretch and others don’t or am I doing something wrong? Doesn’t matter if I mess it up a bit since the transmission cracked in half but it goes 35 mph, does burnouts and wheelies.

I've got a lot of advice about building machines that are experimental, and quite capable of killing you.... I'll just say that whatever you're doing with this thing, make sure that you're never, ever relying on good luck. And before you fix the belt, above and beyond all other issues, make sure the tie rods and rod ends are good and tight. Drop one of those at speed, you and that tractor are gonna barrel roll down the street before you even realized what happened, let alone could react. Less than 200 millisecconds before the first time it lands on you... The problem with that is not that it will kill you (which it could), but even worse, it might not kill you. Solid and trustworthy steering is a good thing.

I've got a couple of ideas on the belt. First off, on an 80 inch belt, I don't think two inches is excessive stretch for normal "run in". You've gotta have that much range in your pulleys. That stretch amount is going to vary depending on the load that it's under, and it sounds like you are applying some load here...

Another issue is wear. Does the "clutch" in this tractor work by detensioning that belt? If so, belt wear is going to occur on the angled faces of the belt, dropping them further into the pulleys, making them loose, when in fact they are still (about) the same length. If that's how this tractor sets in motion (by engaging tension on this belt), you've got the deck stacked against you, as you're starting out "first", it's the equivalent of about twelfth gear on a four speed transmission. That's gonna be high maintenance no matter how you slice it.

What belts are you getting? Belts in the size come in a lot of flavors. From the parts store it was probably a fractional horsepower belt, and over it's limit. Some parts stores keep industrial belts on the shelf. Some of the fancy ones at the farm stores, mostly Kevlar, are designed for the appication, and can handle a bit more "slip" on startup if that's how your clutch works. (A little bit more, that's not a license to control your speed that way....)

You said that the 84 inch belt initially went on with room to spare, right? You should oughtta be able to roll an 82 on there. Set the belt in one of the pullies, transmission in neutral, "hook" one side of the belt into the other pulley, and rotate it around, instead of trying to "place" the belt. It should go. Do note.... If the belt is indeed part of the clutch mechanism, check your final fits carefully, as until it breaks in, your clutch might drag some... Another good way to kill yourself. Do be careful.

 

[Firebrick43]

I got a manual lawn tractor for $80 and like any stupid kid I pulley swapped it (1:2.5 to 3:1) blew a few belts and the replacement one was 2” longer than the original one (very loose without tensioner and needs it all the way out) and after stretching 2” in a minute I had to put on a second tensioner and I got a new belt that was 2” shorter then the original belt 82” vs 84” and it won’t go on so I tried to stretch it and it wouldn’t stretch even a bit, do some belts stretch and others don’t or am I doing something wrong? Doesn’t matter if I mess it up a bit since the transmission cracked in half but it goes 35 mph, does burnouts and wheelies.

Many higher horse garden tractors use Kevlar belts. If you use a standard v belt in their place, yea, they stretch/break fast. Downside is a lot of them cost 80-100 dollars for the belt.