belt drive

[rwirtzfeld]

I have an old Melroe M-500, how does the belt drive work? On the engine there is a pulley that is two halves pushed together with a hydraulic piston. On the other end of the belt it looks to be a centrifugal, snowmobile type, mechanical clutch? What's the purpose of having both pulleys variable?

 

[jerry]

It works the same as a snowmobile except that you control the drive sheave dia with the hydraulic piston. The dia of the driven sheave is controlled by spring tension. The belt will always be the same length so If you make the drive sheave dia larger then the driven sheave has to become smaller thus giving it more rotational speed. The hydraulic part of it has a lot of little parts in it, if you plan to take it apart buy a service manual first. It will make life easier.

 

[rwirtzfeld]

It works the same as a snowmobile except that you control the drive sheave dia with the hydraulic piston. The dia of the driven sheave is controlled by spring tension. The belt will always be the same length so If you make the drive sheave dia larger then the driven sheave has to become smaller thus giving it more rotational speed. The hydraulic part of it has a lot of little parts in it, if you plan to take it apart buy a service manual first. It will make life easier.

So does the more forward pulley with the large spring in the center, engage at some point based on centrifugal force? And then the rear variable speed pulley(one that mounts to the engine crank), changes diameter to vary speed? Sorry, I must be a littel slow on what each one does and when. Randy

 

[jerry]

So does the more forward pulley with the large spring in the center, engage at some point based on centrifugal force? And then the rear variable speed pulley(one that mounts to the engine crank), changes diameter to vary speed? Sorry, I must be a littel slow on what each one does and when. Randy

No, the more forward pulley changes as you change the dia of the drive pulley. When the engine is running they will both be turning, if you move the hydraulic control lever and increase the dia of the engine pulley the driven pulley's dia will decrease and it's shaft speed will increase. The spring is just to provide resistance to the drive force and keep traction on the belt and to close the driven pulley up when you decrease the dia of the drive pulley with the hydraulic cyl. If you did not have the spring and you opened the drive pulley the belt would become loose. If your system is working right you can stand by it and watch it work and it will become clear. Clear as mud?

 

[rwirtzfeld]

No, the more forward pulley changes as you change the dia of the drive pulley. When the engine is running they will both be turning, if you move the hydraulic control lever and increase the dia of the engine pulley the driven pulley's dia will decrease and it's shaft speed will increase. The spring is just to provide resistance to the drive force and keep traction on the belt and to close the driven pulley up when you decrease the dia of the drive pulley with the hydraulic cyl. If you did not have the spring and you opened the drive pulley the belt would become loose. If your system is working right you can stand by it and watch it work and it will become clear. Clear as mud?

Thanks for the reply, I get in now. I can't watch the system work, I bought the M500 with a dead engine, so I'm working on a more modern replacement now. That's why I got to thinking about the variable speed drive, I was talking with another gentlemen, who was replacing the old Kohler engine also, and his plan was to bolt the two halves of the pulley that mounts on the engine together and eliminate the hydraulic portion. So, anyway, he gave up on his old skidsteer so I bought his replacement engine and it had the pulley on it with the halves bolted together, and I asked him about it, and he said it had already been eliminated on his skidsteer prior to the engine transplant project.

 

[jerry]

Thanks for the reply, I get in now. I can't watch the system work, I bought the M500 with a dead engine, so I'm working on a more modern replacement now. That's why I got to thinking about the variable speed drive, I was talking with another gentlemen, who was replacing the old Kohler engine also, and his plan was to bolt the two halves of the pulley that mounts on the engine together and eliminate the hydraulic portion. So, anyway, he gave up on his old skidsteer so I bought his replacement engine and it had the pulley on it with the halves bolted together, and I asked him about it, and he said it had already been eliminated on his skidsteer prior to the engine transplant project.

If he bolts the pulley together it will be at the highest ground speed setting although you could put spacers in to get the speed you like best. The hydraulic cyl is not hard to work on and it is a nice feature to have . The smaller parts in there and the seals are reasonable some of the larger parts are high but if you have access to a lathe you can make them.

 

[rwirtzfeld]

If he bolts the pulley together it will be at the highest ground speed setting although you could put spacers in to get the speed you like best. The hydraulic cyl is not hard to work on and it is a nice feature to have . The smaller parts in there and the seals are reasonable some of the larger parts are high but if you have access to a lathe you can make them.

Thanks for the information. The guy I was referring to, gave up on his project, and I bought his parts. Just trying to decide how to use them best to get my M500 going. I like the idea of keeping the variable drive.

 

[rwirtzfeld]

If he bolts the pulley together it will be at the highest ground speed setting although you could put spacers in to get the speed you like best. The hydraulic cyl is not hard to work on and it is a nice feature to have . The smaller parts in there and the seals are reasonable some of the larger parts are high but if you have access to a lathe you can make them.

Jerry, Sorry to beat a dead horse, but I got one more question about the variable size pulley. I took my hydraulic cylinder apart that pushes the two halves of the pulley together, and your right, pretty easy to rebuild. However, I have a question, the hydraulics push the two halves together, what is suppose to make the halves seperate when the cylinder is not pressurized? Thanks again, Randy

 

[renopker]

Jerry, Sorry to beat a dead horse, but I got one more question about the variable size pulley. I took my hydraulic cylinder apart that pushes the two halves of the pulley together, and your right, pretty easy to rebuild. However, I have a question, the hydraulics push the two halves together, what is suppose to make the halves seperate when the cylinder is not pressurized? Thanks again, Randy

the spring tension on the other pulley is pushing it together causing the belt to shorten and spread the two halves.

 

[jerry]

the spring tension on the other pulley is pushing it together causing the belt to shorten and spread the two halves.

Right, the belt will always stay the same length so as the drive sheave becomes smaller the spring on the driven sheave will close it up and increase it's dia. The speed control comes from the fact that the hydraulic cyl can overpower the spring on the other sheave and as hydraulic pressure is decreased the spring overpowers it as much as it can. does that make sense?

 

[skidsteer.ca]

Right, the belt will always stay the same length so as the drive sheave becomes smaller the spring on the driven sheave will close it up and increase it's dia. The speed control comes from the fact that the hydraulic cyl can overpower the spring on the other sheave and as hydraulic pressure is decreased the spring overpowers it as much as it can. does that make sense?

If you bolt the “clutch” on the engine in one place you will no longer have the ability to vary the ratio. It will be like stickin a 5 speed manual trans in one gear and calling it good enough. No low gear to move the machine in tough situations and no high gear for when you want some speed.
On the 371 I once had I had considered getting a “snowmobile transmision” from hoffco-comet. These are kinda better then the original system as they automatically shift into low gear when the going is tough and into a higher gear when the going is easy.
I ended upselling the machine in favor of a 553, but i don't see why that would not work.
Ken

 

[rwirtzfeld]

If you bolt the “clutch” on the engine in one place you will no longer have the ability to vary the ratio. It will be like stickin a 5 speed manual trans in one gear and calling it good enough. No low gear to move the machine in tough situations and no high gear for when you want some speed.
On the 371 I once had I had considered getting a “snowmobile transmision” from hoffco-comet. These are kinda better then the original system as they automatically shift into low gear when the going is tough and into a higher gear when the going is easy.
I ended upselling the machine in favor of a 553, but i don't see why that would not work.
Ken

Thanks everyone, I'm rebuilding the variable drive right now, I will use it. Just wanted to make sure everything was there, you know how projects go, that have had several prior owners hands in them. I didn't understand what made the two halves of the variable pulley spread back out, but I get it now. Looks like all I need for my hydraulic cylinder that pushes the two halves together, is two seals. I'm calling Bobcat dealer today, to see if I can get them and how much they would be nice enough to let me pay. You guys are a big help, Randy

 

[gymsbyjo]

Thanks everyone, I'm rebuilding the variable drive right now, I will use it. Just wanted to make sure everything was there, you know how projects go, that have had several prior owners hands in them. I didn't understand what made the two halves of the variable pulley spread back out, but I get it now. Looks like all I need for my hydraulic cylinder that pushes the two halves together, is two seals. I'm calling Bobcat dealer today, to see if I can get them and how much they would be nice enough to let me pay. You guys are a big help, Randy

rwirtzfeld A little off the subject but if you are getting rid of the 2cyl. Kohler...do you have any interest in selling the carb and coil off it? Joe

 

[rwirtzfeld]

rwirtzfeld A little off the subject but if you are getting rid of the 2cyl. Kohler...do you have any interest in selling the carb and coil off it? Joe

I would, can't speek for the condition of them, never ran the engine, just pulled it out to replace it. You can email me at [email protected] Thanks, Randy

 

[gymsbyjo]

I would, can't speek for the condition of them, never ran the engine, just pulled it out to replace it. You can email me at [email protected] Thanks, Randy

Email sent. Joe

 

[bjohnson]

Thanks everyone, I'm rebuilding the variable drive right now, I will use it. Just wanted to make sure everything was there, you know how projects go, that have had several prior owners hands in them. I didn't understand what made the two halves of the variable pulley spread back out, but I get it now. Looks like all I need for my hydraulic cylinder that pushes the two halves together, is two seals. I'm calling Bobcat dealer today, to see if I can get them and how much they would be nice enough to let me pay. You guys are a big help, Randy

Hi Randy; I realize this post is rather old, but I couldn't find another option. I have a M500 that is missing the Variable Speed Sheave. I'm planning on replacing with a fixed/adjustable sheave. What I'm looking for is the OD of and existing sheave to work from. If you or anyone else on this forum could take some measurements for me I would greatly appreciate it. Thanks Brett

 

[gymsbyjo]

Hi Randy; I realize this post is rather old, but I couldn't find another option. I have a M500 that is missing the Variable Speed Sheave. I'm planning on replacing with a fixed/adjustable sheave. What I'm looking for is the OD of and existing sheave to work from. If you or anyone else on this forum could take some measurements for me I would greatly appreciate it. Thanks Brett

Where are you located Brett?

 

[bjohnson]

Where are you located Brett?

I'm located in Vancouver, BC, Canada. Brett

 

[gymsbyjo]

I'm located in Vancouver, BC, Canada. Brett

You are just looking for the diameter? I was going to say if you were local you could check mine out, but I'm in NY State.