Rack saw

[agrimog]

john, if you must use a flat belt, why not set up a jackshaft arrangement,and connect the tractor pto to the jackshaft input

[agg221]

Crowned pulleys will take quite a lot of misalignment - you can pretty much just set up by eye and it will run fine, maybe with a bit of slight twisting so I wouldn't have anything locked in place until I had pulled it over a few times. The only problem is if you have uncrowned pulleys for a 'fast and loose' arrangement, which uses a cage around the belt to slide it, and at the same time stops it jumping.

 

Dad and I used to run an old Denning sawbench with uncrowned fast and loose pulleys, using a Lister B. The bench had lost its cage for sliding the belt across and to get the running speed right for the blade we had to run off the flywheel on the engine, so everything was uncrowned. We used old fire hose as a flat belt, with a wire lacing, so it was about as crude as you can get. We didn't have any problems with it jumping off.

 

Alec

[renewablejohn]

Crowned pulleys will take quite a lot of misalignment - you can pretty much just set up by eye and it will run fine, maybe with a bit of slight twisting so I wouldn't have anything locked in place until I had pulled it over a few times. The only problem is if you have uncrowned pulleys for a 'fast and loose' arrangement, which uses a cage around the belt to slide it, and at the same time stops it jumping.

 

Dad and I used to run an old Denning sawbench with uncrowned fast and loose pulleys, using a Lister B. The bench had lost its cage for sliding the belt across and to get the running speed right for the blade we had to run off the flywheel on the engine, so everything was uncrowned. We used old fire hose as a flat belt, with a wire lacing, so it was about as crude as you can get. We didn't have any problems with it jumping off.

 

Alec

 

Alec

 

Thanks for that. It is this cage arrangement which is already on the rack saw and still works which I intend to use. The MF 65 pulley I am using normally bolts directly onto the pto shaft using the 4 bolts normally keeping the lifting arms from swinging to wide. I will be attaching the pulley directly to the existing frame using the 4 bolt holes in the pulley mounted to two lengths of angle iron which will be adjusted by threaded rod to get the correct alignment and tension. It will then mean the saw is permanently connected to the pulley so will not need aligning every time we use it and we dont have to be that precise locating the tractor to connect the pto shaft. Hope that makes sense

[agg221]

Yes, it makes sense.

 

Is the MF65 pulley crowned? If so, you may have to think around this one. A crowned pulley will try to run the belt in a single place, whereas flat pulleys will will run anywhere. If you run crowned one end, flat the other, and want to use the fast and loose arrangement, you will end up rubbing the belt sides a lot as the crowned pulley tries to pull it back - you can set it for one or the other, or for a compromise which will rub in either case.

 

The reason we had to run off the flywheel was because we were running a 19" blade on a 24" saw. The original pulley was still in place, and was an uncrowned, double width pulley, which I think is what you would need.

 

The other option would be to align it with the 'fast' side and use the PTO to engage/disengage.

 

Of course, if the pulley is uncrowned then you don't have a problem in the first place:001_smile:

 

Alec

[renewablejohn]

Dont really know whether you would call it a crown pulley but putting a flat rule over the pulley theres approx 1/4 of an inch on either side so not perfectly flat. I presume it will need a longer belt and mount inline with the drive pulley.

 

Certainly could engage disengage with pto but thought from safety aspect would be better If I could still use the idler pulley as the control lever is next to the rack handle.

[agg221]

Yep, that's crowned, and as such it will always want to run in a single place - you can't actually make the belt long enough to counter this as it will want to run 'straight' so will run at a fixed point at the other end.

 

The simplest option would be to align it with the 'fast' on the saw and leave it there, but if the MF pulley is as wide as the pair of pulleys on the saw, ie there is enough width to allow the belt to run in either location, you could get it skimmed down flat so it would let the belt slide.

 

Alec