cork bandsaw tyres -what is the best method to create crown

[RobinBHM]

I'm replacing some bandsaw tyres soon and been thinking what would be the best way to create a crown.

A few months ago I bought some urethane tyres from the US. These havent been successful. They are supposed to be tight enough to stay on, but that didnt work, so I glued them on with contact adhesive, but they still came off. Ive now managed to get them to stay on, but the blade wont track well. The tyres are too thin really to form a crown, hence Im now trying cork.

I need to make the new tryes concentric first and then form a crown.

Could I use a parting tool? Or use a sanding block? I actually used a router on the urethane to make it concentric, it worked but tricky to clamp on.

This is the cork

http://scosarg.com/50mm-wide-rubber-cork-m

TIA Robin

 

[blackrodd]

This is the first time I've heard the urethane tyres not working, I would say the tyres were too big, or the wheels dirty.
Bearing in mind you're an experienced operator, I would say the tyres were too big
If its the bandsaw tyre warehouse, they will do a free replacement..
I would say The cork is too delicate to use as a tyre, there's a lot of tyre and blade stress going on when sawing,
resulting in the cork easily tearing.
I think you will also have problems with a suitable adhesive and as far as I can remember cork is cut or sliced and not turned, but may well be wrong on that one.
HTH Regards Rodders

 

[RobinBHM]

Hi Rodders,

Yes I wondered about cork being too delicate, but Scot and Sargeant sell cork for this application. It is harder than cork as it is impregnated with rubber.

I decided to try the cork material instead as it is much thicker so allowing plenty of thickness for machining down. The wheels run slightly out of true which doesnt help. I did come across 6mm x 50mm neoprene and wondered about that, its 60 shore hardness but Ive no idea if that would be the right hardness. They are cast iron wheels.

I also wondered how much crown. I read somewhere that it should be equal to a sphere of the same diameter as the wheels. The wheels are 610mm dia x 50mm wide, which by doing a chord calculation gives a crown of 1.2mm

 

[blackrodd]

I can't remember if there was a formulae, but I certainly remember the bigger bandsaws well, and in my minds eye,
You're quite probably correct.
Our small bandsaw, was referred to as 30" bandsaw, as the wheel was 30"across and the moulded rubber tyres were quite thick and only slightly crowned.
What adhesive have S&S recommended?
Regards Rodders

 

[Steve Maskery]

Were your previous tyres crowned? On some machines the crown is so slight it may as well not be there (like mine), and indeed, I have seen machines which I would swear had no crown at all. I've also seen wheels where the crown is formed by the rim of the wheel itself, underneath where the tyre sits, so the flexible (rubber) tyre just hugs it.

Even plain flat tyres can be tracked successfully, because once the wheel is tilted, the surface of the tyre is at an angle, just as it would be if it were curved, and if the blade is narrow (as it is on all our BS, compared with, for example, an industrial resaw), the amount of curve underneath it is virtually zero, compared with the curve swung by the plane of the wheel.

What I am saying is that I wouldn't get too hung up about the crown at this stage. See how it goes. If you can't track it at all then use a sander on it whilst you turn it by hand.

 

[wallace]

On my wadkin DR30" the tyres are vulcanised. When I restored it I made a little tool rest and clamped it on and used a big turning scraper. I also tried the sand paper on a longish flat stick and used a levering technique. Both methods worked well

 

[woodpig]

^^^ What Steve said.

 

[Beau]

Fixed up my old Wadkin with cork from Scott and Sargent. Works perfectly. For creating a crown I removed one of the wheels and it's axle. Then set it up horizontally on my bench and used a belt sander to create the crown while turning the wheel.

 

[woodpig]

Clever.

 

[RobinBHM]

Many thanks for all the advise.

Its useful to hear somebody else has used the cotk successfully.

Annoyingly blades tracked fine on the orignal tyres, although these were really worn and had deep ruts. Since changing them the blade keeps coming off, either it works its way forward or works back and rubs on the rear guide. Hence why I want to try a crown.

The machine is an old Dominion AKA 24, which has a cast frame, 24inch wheels. Its quite a crude machine with 2 spanners needed to adjust tracking. I hope with a bit work it could cut really well.