Toro Drive sprocket upgrade
#1
07-18-23, 10:27 AM
Toro Drive sprocket upgrade
I have a 1989 Toro HMR 1600 Model 55620 zero turn mower that was made only one year (1989) If you own one you know why lol I still like to drive it, and I have replaced or rebuilt everything in the past few years. One thing developed as it neared completion was that the drive chains would like to jump a link or two on the small drive sprockets that are attached to the two Peerless gear drive transmissions in tight zero turns. A friend has suggested a bigger set of the small sprockets but I have no Idea where to look for larger sprockets that would fit up on set up this old.. (I know this mower was the reason manufacturers went to hydraulic motors in the wheels to drive zero turn mowers lol)
#2
07-18-23, 11:52 AM
Group Moderator
I have no knowledge about your mower but sprockets are very easy to find. You can just search online. There are many suppliers as they are used by industry and machinery a lot. I would look at "wear resistant" or sprockets that say the teeth are hardened for longer life. McMaster Carr is a good place to start. There are a few things you will need to know to start your search:
chain type/size
number of teeth
bore size
If you can't find the correct size bore or keyway to match your axle it is a pretty straightforward job for a machine shop to bore it out to what you need and to cut in a keyway.
When you look at the spec for the sprockets you'll also usually see the outside diameter (OD) listed. That will help determine if it's too big to fit the space. Keep in mind that changing the number of teeth on the sprocket will change the speed so you should replace both so driving doesn't seem lopsided. I assume the small sprocket is on the gear box. In that case going to a larger sprocket will provide faster speeds, less torque and will put more strain on your gearbox. To offset that you could also change the driven sprocket to keep the same ratio, but that's more work.
chain type/size
number of teeth
bore size
If you can't find the correct size bore or keyway to match your axle it is a pretty straightforward job for a machine shop to bore it out to what you need and to cut in a keyway.
When you look at the spec for the sprockets you'll also usually see the outside diameter (OD) listed. That will help determine if it's too big to fit the space. Keep in mind that changing the number of teeth on the sprocket will change the speed so you should replace both so driving doesn't seem lopsided. I assume the small sprocket is on the gear box. In that case going to a larger sprocket will provide faster speeds, less torque and will put more strain on your gearbox. To offset that you could also change the driven sprocket to keep the same ratio, but that's more work.
WML13
voted this post useful.
#3
07-18-23, 01:39 PM
All of the specs will be easy to line up, and doing both sides was pretty much a given considering what was happening that prompted the post in the first place. Since the chains are new, and I had to cut them to fit the originals, I just hope there is enough chain left to accommodate whatever i find to replace the two little sprockets!
Thanks for the reply!
Thanks for the reply!
