Belts

[Heritage]

Boy am I glad I found this forum! I have recently been given a bt3000, and it doesn't seem like it runs "right". The saw loses power and slows down even when it is not cutting anything.

I put a new blade on and that didn't help, didn't think it would but it needed to be changed any ways. So I proceeded to look at the belt, and I noticed that the notches were on the outside and not making contact with the gears.

Is that right, it sure doesn't look right to me but I am not sure. Any help would be appreciated.

[toolguy1000]

i've no idea, although if they are cogged belts, shouldn't the cogs rest in the pulley? hoping this will help, here is a copy of the owners manual for that saw:

http://bt3000.com/Manuals/BT3000-Manual.pdf

[mpc]

It's been a long time since I looked at the belts on my saw... but my recollection is the "wwwww" shape rides against the pulleys, the rectangular notches are outside. Look at the metal pulleys - whatever grooves/shapes they have will match the correct side of the belt.

Even if the belts are twisted inside-out, that won't make the motor speed vary. Especially if you're not cutting anything - just letting the blade spin. The BT3 saws run the blade at higher RPMs than most other saws too by the way - 4800 RPM compared to the more common 3600 RPM. Keep this in mind when buying blades. Cheap blades may not be rated for 4800 RPMs; some dado sets as well.

Motor speed issues come from:
1: sawdust build-up inside the motor - especially fine dust. As the motor runs and gets warm, thermal expansion causes "almost tight" gaps to become "tight" non-gaps.

2: electrical supply issues. Are you using an extension cord? If so, it MUST be a beefy cord designed for high amperage tools. Otherwise the cord will have too much electrical resistance, denying the saw the power it needs. Plus the cord will warm up a bit (converting that "stolen" electrical energy into heat) - so, after the saw runs and slows down, shut it off and unplug everything. Feel the cord for warm spots - including the ends. If you find a warm spot, that cord is BAD or at least too small for power tools.

3: worn contacts on the saw's power switch. The original BT3000s have a two-button switch assembly (that was recalled by the way - call Ryobi and they'll swap it!) and later models have a smaller rocker switch with a cover plate. Either way, the contacts inside the switch can arc each time the saw is turned ON or OFF... slowly burning the contacts away and/or coating them in charred carbon ==> resistance. Quick test: unplug the saw's stubby cord from the side panel and plug that into a beefy extension cord, then plug the other end of the extension cord into a wall socket. If the motor runs better, your saw's internal wiring/switch need attention. Do NOT use the saw like this though - just do the test!

4: poor wiring in your house/garage electrical wiring or wall socket. Plug a regular desk lamp into the same wall socket as the saw and turn it ON. Then turn on the saw. If the lamp dims, the wiring is weak. Let the saw run until the motor slows a little, if the lamp is dimming too then it's poor wiring building up resistance (and heat!) denying your saw working energy. This is a dangerous situation in the house/garage wiring that needs a pro electrician to check/repair.

5: bad bearings in the motor or saw arbor. If you hear a grinding sound, or a sound like marbles rolling around a metal coffee can, then the bearings are suspect. They're standard bearings - readily available at NAPA type of stores, McMaster-Carr, Fastenal, etc. - any decent hardware or car parts store. Look at the outer edge of the bearing; you'll see letters & numbers stamped into them - just buy a bearing with those same numbers. Bearing numbering is standardized across manufacturers so everybody uses the same numbers.

mpc

[Knottscott]

Check the brushes too.

[LCHIEN]

i think the grooves on the belt should be engaged to the grooves on the pulleys. The grooves run around the outside of the pulleys and along the length of the belt. There are some tooth-like projections on the outside of the belt across the short dimension but they don't engage anything.
There could be other reasons - especially if the previous owner was screwing around with the belts then he may have been fighting other motor-related problems.

[big tim]

There are grooves on the inside as well as on the outside of the belts, look at the pictures below:



The inside grooves engage the grooves on the pulleys
Here is a picture of the arbor pulley



Hopefully this will help you to find out if the belts on your machine are installed correctly.

Tim

[Heritage]

Thanks for the quick responses, I took the saw apart today and noticed the grooves in the shafts. Before I had looked at just the top of the belt and saw the notches and assumed it was wrong .

I felt the wiring may be suspect too so I checked the receptacle that it is plugged into (no drop cord direct connection), and I get a consistent 125 volts just like I always have. The switch had been replaced with a key switch and the original switch wires are spliced together. I had already intended to replace that with the appropriate switch.

Bearings and brushes are in good shape too. Just learned today though that this saw was used by a siding company and the belt had a lot of vinyl dust in it, but not the motor.

Hopefully the dust is the problem because I think this saw could be good for me.