Start Rite 352 drive belt problem

[Sisyphus]

I have an old 352 ( the manual refers to a change of telephone number for Startrite in 1987 ) and it has worked well for years.
Unfortunately, I had to change the drive belt a few weeks ago, and while it worked ok for a time, the belt now comes off the pulley on the motor shaft with monotonous regularity. It is a nightmare job getting it back on and I have had to do it three times today.
The pulley is attached to the motor shaft by putting a spline into matching grooves on both the pulley and the drive shaft. There is a hole in the rim of the pulley which takes two grub screws. The first tightens against the spline to hold it in place and the second is then screwed down against the first presumably as a belt and braces operation. I had to replace the drive belt about three years ago and I did this by using a ruler to get both the pulley wheel and the lower bandsaw wheel in the same plane and then tightened everything down. This worked fine until a week or so ago when I had to replace the drive belt as it was torn, but what happens now is that it works fine for a minute or so or an hour or so and then the belt comes off the lower pulley. I can see that this is because the pulley has moved out from where I set it originally ( in the same plane as the large wheel ) to the end of the shaft and I assume that the offset is enough to take the belt off the pulley.
I have made sure that the grub screw is tightening down on the spline rather than just going into the groove on the shaft and that it is as tight as I can get it. I assume that this must be the right thing to do as otherwise the spline would just come out. I have also ensured that the motor is held firmly against the body of the bandsaw by tightening the adjusting lever at the back as tightly as I can.
I am now out of ideas and would very much welcome any thoughts. It may well be that, like its owner, the bandsaw is feeling its age, but it has always ( up till now ) been a solid and reliable machine and I would not like to have to replace it.

Sisyphus

 

[Myfordman]

I think you have got to tighten the pulley so that it cannot move. If the current screws are slotted, swap them for cup point, allen head ones which can be tightened far more and will also grip better.
If the pulley is diecast aluminium, it may well have fretted against the shaft and become oversize. when the screws are loose, it should still be a tight fit on the shaft. if it can wobble at all then I suspect this is your problem.
Get a local tame engineer to look at it to assess the problem from an engineers perspective.

 

[Sisyphus]

Thanks for your comments. I think the pulley is still ok as it is a very tight fit on the shaft. The existing grub screws are Allen heads. However, I noticed that the spline slides in and out very easily. do you think that this could be the problem?
I like your idea of a tame engineer. There must be one in Glasgow but I have no idea how I would find him. I shall make some enquiries.

Sisyphus

 

[beech1948]

You diagnose the problem in your first message. The pulley and the wheel are no longer in the same plane. The belt is coming off because of the sideways force placed on it.

The solution is to realign the wheel and pulley and screw down the grub screws using some pointed one's if necessary. Clean off any old burrs with a fine file. Leaving the pulley where it is will result in continued drive failures.

You should be able to reposition the pulley by first taking it off and filing down the burrs......if there are any.....from the pulley dragging along the shaft. Replace.......put shaft end on ice or use a plumbers freezer pack.....heat up the pulley on an incandescent Lampson.....join two parts, position and screw down into fresh steel.

Hope this helps. Al

 

[paulm]

I still have the original motor from my machine that I kept when I upgraded to a more powerful motor a few years back so I had a quick look at it and it's the same as you described, with the grub screws pressing onto the spline to press it into the groove on the shaft, so you're doing that bit okay.

Cheers, Paul

 

[andersonec]

Try this number, I have used them in the past but I think they may have moved but the number should connect.

Andy

http://www.altsawsandspares.co.uk/contact.html

 

[Sisyphus]

Thanks for the comments but I am sorry to say that I am still having problems. In fact, I've had more fun pushing that boulder up the hill all day than trying to sort this out.
I think I now have another problem but am wondering if I am just confusing myself and hoping that you can help me sort this out.
To try and explain, I show a couple of photos.

The back view shows the plate which holds the motor to the body of the machine. There are two handles. The one in the centre holds the support bracket firmly against the machine. The other one is a cam mechanism for raising and lowering the motor. The inside view shows the other side with the belt set in the slow speed position.

I have two problems here. The first is that the cam does not allow the motor to be raised beyond the protruding vertical edges on the bottom plate. This means that the belt is exceedingly tight and can only be put on with the assistance of someone else and a large crowbar. The second is that I cannot see any way of running the saw at slow speed. This is because the motor shaft comes through a notch in the machine body and it is impossible to get the shaft low enough to get any tension in the belt. You can see this clearly in the Inside View where the shaft is touching the bottom of the notch but there is no tension in the belt.

I am very probably being stupid here but I just cannot see how this can be right. I never thought about it before, but for years I have been cutting logs up to a foot in diameter on the high speed. In my travels today I actually looked at the instruction plate on the back of the machine and it says that I should be cutting them at the slow speed, so I really would like to know how this can be done.

This takes me back to my original question. Beech 1948 has summed up the position exactly when he says that the sideways force exceeds the holding grip of the grub screws ( it is also ripping one side of the belt ). I measured it all up again today and discovered that I did not in fact have the pulley wheel and the saw wheel exactly in the same plane. I also found that this was not due to lack of trying on my part. I think the reason is that the motor shaft is at a very small upwards angle, ie it is not at a right angle to the body of the machine and hence the saw wheel. The alternative is that the saw wheel is now off true although I struggle with this as it would surely affect the tracking and the blade worked fine on the few occasions I actually got it running.I have no idea why but assume it must have been like this through the earlier trouble-free years.

Any thoughts on this would be most welcome. My own have got no further than trying to pack out one end of the support flange, or adjusting the four screws holding the motor to the flange, so that the motor shaft points downwards very slightly.

My problem is that I have no idea what I am doing. I feel I am missing something blindingly obvious here and would be eternally grateful if somebody could tell me what.

Sisyphus

 

[beech1948]

Its easy to get the "apparent" problems just build and build. Consider that the motor has worked well for a considerable period of time with the pulley having a small upward angle. Its probably not significant as the motor mounts have not been touched for many years.

I would align the wheel and pulley, ignore the angle of the pulley for now, and try it out. If you can run OK then that problem is solved. You should probably consider refixing the pulley with a hardened pointed grub screw and make sure you screw into new steel and not into the old grub screw marks. Thats unless you want to drill a small ( I mean short) hole to set the grub screw into but be careful to keep to a minimum.

I suggested that you take the pulley off and clean up the grub screw burrs. If you do this then check to see that the motor shaft is still straight...a small upward angle should be OK.

can't help with the speed adjustment issue as my 352 has been used only on the slow speed.

 

[Lons]

I have a 352 and not had any problems but i would put in the grubscrews with theadlock and I think you can get a tube of similar "stuff" to stick the pulley to the shaft without it being permanent. Seem to remember it used for bearings.

 

[andersonec]

I have an old 352 ( the manual refers to a change of telephone number for Startrite in 1987 ) and it has worked well for years.
Unfortunately, I had to change the drive belt a few weeks ago, and while it worked ok for a time, the belt now comes off the pulley on the motor shaft with monotonous regularity. It is a nightmare job getting it back on and I have had to do it three times today.


Sisyphus

I knew I had this somewhere and finally found it, don't know if it's any use but have a look anyway. Your model's handbook is listed.

Andy

http://www.altsawsandspares.co.uk/spares.html

 

[woodpig]

The first picture shows a very loose belt but you go on to say:
"This means that the belt is exceedingly tight and can only be put on with the assistance of someone else and a large crowbar" ?

 

[Racers]

Is the motor pulley the wrong was round? shouldn't the big pulley diameter be for the smaller bandsaw pulley and vice versa?
That would give you the same belt tension.

Pete

Just checked the on-line manual page 19 shows the motor pulley with the large diameter towards the front i.e. the end of the motor shaft.

 

[woodpig]

Is the motor pulley the wrong was round? shouldn't the big pulley diameter be for the smaller bandsaw pulley and vice versa?
That would give you the same belt tension.

Pete

Just checked the on-line manual page 19 shows the motor pulley with the large diameter towards the front i.e. the end of the motor shaft.

Yes, you're right. He's got the pulley the wrong way round. :lol:

 

[SurreyHills]

On my 352 there is one lever to lower/raise the motor, I don't have the second lever shown in your photo. Can't help much with the pulley arrangement as mine had been converted from 3 phase to single phase and has a set of what can best be described as "homemade" pulleys. Not sure if my pulleys are the correct size and have never been happy with the cutting speed - so may revisit trying to fettle mine. Do your pulley looks to be original?

 

[Racers]

More like Sillyphus than Sisyphus :wink:

Pete

 

[Sisyphus]

Gentlemen,

I am shamefaced. In my defence, can I say two things. First, the machine came that way when I bought it. Being a retired accountant and not a woodworker, I knew no better. Second, i had come to the same conclusion myself after I reasoned that the obvious solution to the belt being too tight was to buy a slightly longer one. This left me with the niggling doubt that I would then have to buy a shorter one to change the speed but I pushed this aside in my desire to deal with a large pile of oak and chestnut logs.

The bigger belt came yesterday and fitted easily. I used the cam to tighten it and it worked fine for a couple of minutes before coming off. I then had my light bulb moment and turned the pulley round, whereupon it came off even faster. I then tried Thread Lock and some stuff called Quik Steel to keep it on but had no luck. I must confess that the word "dash" was heard occasionally during the day. By this time the pulley and the key were becoming easier to get on and off so I thought that had probably damaged the motor shaft and its groove with all the messing about although it seemed to be slightly better when I had the belt between the two big wheels.

More in hope than anything else I ran some super glue round the shaft and pulley and left it overnight. I have just been trying it and it seems to be working. Obviously it is not correct and I assume that it will eventually come off. When it does, I will probably go for a bigger motor with a new key and pulley.

One of my partners usedto tell me that there were no mistakes, only learning experiences. I doubt that my clients would have seen it that way but this has certainly been a learning experience for me and made a pleasant break from pushing the boulder.

Thanks for all your help.