crown on drive wheel

M

miden

Joined
Sep 9, 2005
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Guys, can someone please advise what sort of crown should be put on a belt grinder's drive wheel?
I have problems with the belt scooting off to one side when I apply pressure when grinding - I was told that this could be due to the fact that my drive wheel is flat.
Any advice will help.

thanks
 
miden said:
Guys, can someone please advise what sort of crown should be put on a belt grinder's drive wheel?
I have problems with the belt scooting off to one side when I apply pressure when grinding - I was told that this could be due to the fact that my drive wheel is flat.
Any advice will help.

thanks
Click to expand...

Which grinder do you have?

Unless you made the wheel yourself, it should have some crown already.


Most common is a couple, to a few degrees per side with maybe an inchish of flat in the middle.
Some just put a layer or two of tape in the middle as a temporary measure or test.



First try more belt tension.
Belt tension is almost always the answer to tracking problems.
 
You couod check to see if all the wheels are in the same plane. 3 points are coplanar but 3 wheels are not necessarily. just a thought.
 
Real easy to try. Use some ordinary ( Tan? coloured ) masking tape and try four or five layers.The wheel alignment thing is very important, as is the spring tension. Did this problem just start? I suggest you crown the idler wheel if you have one. Frank
 
Sam, I made the grinder and the wheel myself and there is no crown, flat as the prairies.
I have reasonable belt tension - would too much or too little tension cause the problem?

PT Doc, the wheels are pretty much in the same plane.

Frank, no, the problem didn't just start, it has always been there. I figured I will make a new wheel, larger diameter as well to get better surface speed on the belt so while I am about it I figured I should crown the wheel as that may solve the running off problem.
I presently have a 7" wheel. There isn't an idler wheel.

Thanks for all the advice guys, I will start by trying the tape idea.

Thanks again.
 
low belt tension is usually the problem with tracking. I'd get a stronger spring as well as crown the wheels with tape.
 
Even an old belt that you can't see but is stretched badly will cause that problem. By the way a 7" drive wheel will probably create a belt speed you can't work with. That would be super fast ! Frank
 
Thanks jawilder, I just saw later that Sam had in fact advised that too so I asked again. Thank you and Sam.
Frank, the motor is running at 1740 rpm, do you really think that is super fast with a 7" wheel?
I have been laughed at on this same forum because some guys thought that was granny speed.
I have ground a number of blades with things like they are and I have personally never thought it too fast.
Not getting defensive, just curious. Please let me know.
thanks

Mike
 
It's only too fast if you're burning stuff up. If you can grind just fine with the speed you use then nothing's wrong.

Just curious, are you slack belt grinding?
 
I am running a 1750 rpm motor and a 6 inch drive, at 1:1 thats really only about 2800 sfpm. I just watched a video with Ray Ennis grinding blades at 7500, which frankly would scare the life out of me. From my limited experience i find that a crowned tracking wheel has been more important for straight tracking than a crowned drive. Others opinions may vary.
 
The idler wheel is the one you crown and it should be the last wheel the moving belt surface encounters before the spot where work is done (platen or contact wheel).
Not sure crowning the drive wheel will do what you want. One wheel steers with the crown and the other wheel(s) are there for drive and/or work surface (contact wheel).
That and decent tension to keep the belt engaged with the crown... everything tight and planar and you should have no problems.
 
fumbler, I generally don't apply very much pressure and do not overheat the steel so I have never had things burn except with a smooth belt. However, and this will reply to Frank and Grayzer86 as well, the faster things are moving, the faster screw ups happen too.;) Grinding at 7500 fpm would scare the life out of me too, the guy that is doing that must be very confident.

Jcaswell, my grinder doesn't have an idler wheel, it is a home built job and only has a drive wheel and a contact wheel, nothing inbetween.
It has a pretty effective tracking system the (motor swivels by means of a hand screw underneath which tilts the motor) which I can align the 2 very well but they do not stay aligned, or, they stay aligned until I put pressure on the contact wheel.
Generally, when I apply pressure it runs off and then returns somewhat when I remove pressure.
If I could figure out how to post pictures then I would post one to show you.:confused:

Anyway, thanks to all of you again for taking such an interest.

Mike
 
That sounds to me like your frame may be flexing. Its an issue that is common with the small and cheap 1x30 units. The issue is likely that the belt slowing down induces torque into the upright arm, or horizontal depending on your design, and this causes the drive and contact to temporarily come out of alignment with each other and no longer be running perfectly parallel.
 
Just thinking aloud here. You basically have a two wheel grinder. I don't know how the Coote grinders are set up, but that might be a place to start.

On my craftsman 2x42 the drive wheel has about 1/16" over 1" drop per half the wheel's width. Tracking is by the top wheel's adjustable tilt. It is also crowned.

Sounds like maybe modifying your design to accommodate a tension/tracking wheel might be the ticket.
 
Love to see pix.
So it's direct-drive and tracking--interesting.
Under those circumstances, obviously the drive wheel is the one to crown.
I'm kind of suspecting flexing at your idler/ drive arrangement This is going to want to be really rigid. Because leaning on the belt under power is going to make the motor/idler move accordingly.
Just a thought.
 
To post pictures, you can use a hosting site such as photobucket.com then post a link to the picture.

It could be flexing such as Grayzer suggested. It could also be that your tracking mechanism is moving as you apply pressure. Have you added the tape to crown the wheel yet? It only takes a couple of seconds to do and that will tell you if it was the problem.

My money is still on the tension. Do you hear a "twang" if you pluck the belt like a guitar string? Throw some more springs on it and see what happens.
 
Hi guys,
I just tried the tape on the wheel thing - I didn't have masking tape in the shop so I just used some electrical tape, 3/4" wide and put 5 turns on the centre of the wheel. Eurika! It worked amazingly well.
I ground a piece of steel and there was no scooting off to the side. I forced the steel against it so hard that the lights dimmed and the belt didn't slide a millimeter! I was amazed, what a difference.
Thank you Frank, Sam, thanks for suggesting the tape.
Fumbler, no, I am not slack belt grinding, it is direct against the contact wheel.
Jawilder, there isn't a twang when I pluck on the belt but it is pretty tight.

Thanks again to all of you guys for taking the interest and the trouble to advise a fellow maker, I will go to bed much wiser and happier tonight.

I will see what I can do about figuring out how to post pictures then I will post one of my grinder, be warned, it is not a work of art but now it at least doesnt lose the belt.
Time to make that new contact wheel with the crown!

Mike
 
Seems like a fine made grinder. Get some masking tape. The electrican's tape won't last long but the masking tape sure will. Frank
 
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