DoAll bandsaw - needs some work

[cnc-me]

Check this out, his saw is bigger, but Im sure you can pick up on something.
https://www.garagejournal.com/forum/showthread.php?t=34928

 

[matt_i]

That was once a great thread but its current value is next to zero with all of the pic links broken.

 

[Hagatronics]

Time for an update...

I've had the gearbox in, out and apart three times. I just can't get it to shift between gears reliably. It will either be in high and smash dogs going into low or vice-versa. With careful fiddling of the selector shaft by hand and slow manual rotation of both the input and output wheels I can get it to stay in one or the other gear.

Also, after about 5 minutes of running the motor slows down and then stops. Need to wait until it cools off before it will start again. Eh, it's 74 years old - I figured it's done it's time.

My original plan was to put in a VFD and replace the Reeves drive. But with the gearbox locked into one speed a VDF alone won't get me the speed range of 50fpm to 1600fpm I'd like. For now I'm putting in the VFD, keeping the Reeves drive and just locking the gearbox into high gear. A bit of lubrication got me the full range of speeds from the Reeves drives and it adjusts easily.

I purchased a 2HP motor and VFD today which is nearly triple the original 0.75HP motor. That gives me 'full' power (compared to original) or more from 15Hz (400rpm) through to 140Hz or 4000 (rpm) where the motor is rated to.

By my calcs I get (using 50Hz input power).

- 55fpm at 0.75HP (15Hz and Reeves drive geared all the way down)
- from 185fpm I'm getting the full 2HP
- top speed is 2600fpm which is over 1000 more than the original saw. (140Hz or 4000rpm which is the motor limit). This gets me well into wood cutting territory. I'll probably limit it to 1600rpm where the speed gauge tops out.

Most of my cutting will be in the 150-300fpm range which means I can set the Reeves drives and just tweak the variable speed up or down 30% whilst still in the full power range of the motor.

Next job is to mount the VFD, programming and wiring. I've got a cool plan for modifying the original speed dial that requires a Hall effects sensor, Arduino and a servo motor. Standby.

 

[matt_i]

I think its completely reasonable to expect to have to "sync" the transmission just like you'd do on a lathe when changing the headstock gears by jogging one of the shafts back and forth. So then you'd just need a mechanical detent to keep the selector where you want.

I have to admit the two dual-speed bandsaws I use are always locked in low gear for cutting metal and so I haven't shifted them.

On the bandsaw I converted, I sourced an Allen Bradley 800T potentiometer - 30mm size (there are several ranges, best to consult the catalog and match as closely as possible to the VFD). These aren't cheap new but fit perfectly into the same punchout in the panel. Automation Direct has cheaper models in the 22mm size. I think I tried to get 100sfm to be "exact" as far as calculation at 30Hz and then let everything else flow from there...exact surface speed numbers are not required for cutting

 

[dkmc]

T
I've had the gearbox in, out and apart three times. I just can't get it to shift between gears reliably. It will either be in high and smash dogs going into low or vice-versa. With careful fiddling of the selector shaft by hand and slow manual rotation of both the input and output wheels I can get it to stay in one or the other gear.

It's certainly your project and your money. But what you are describing sounds like normal operation of the gearbox. Turning the band wheel by hand is always required to get the gears to mesh when shifting. It's a very simple gearbox with no 'syncros' or anything to aid in shifting gears smoothly. If it's staying in the gear selected, it's working as designed. But if the OEM motor is shutting down from overheating, there may be other problems there.

 

[danski0224]

That was once a great thread but its current value is next to zero with all of the pic links broken.

One reason why attacments should be uploaded here, not linked to a picture hosting site.

 

[DocsMachine]

Not clear from your description, but you're not shifting gears under power, are you? The standard method is to shut it off, and then flip the lever. Low to high on mine is usually easy, high to low usually takes a little jogging of the wheels.

And on mine, the lever itself retains the shifting rod in position. I honestly don't know if mine would "pop out of gear" if the lever were gone, but with it in place, it basically can't switch on it's own.

Doc.

 

[Hagatronics]

Not clear from your description, but you're not shifting gears under power, are you? The standard method is to shut it off, and then flip the lever. Low to high on mine is usually easy, high to low usually takes a little jogging of the wheels.

And on mine, the lever itself retains the shifting rod in position. I honestly don't know if mine would "pop out of gear" if the lever were gone, but with it in place, it basically can't switch on it's own.

Doc.

As you describe I can shift using the lever and with the saw off, being manually turned. Even with the shifting rod in position it pops out of gear when the saw is turned on and under load. I suspect that there is insufficient throw from the selecting rod to sufficiently engage the dogs. When I pack it with spacers etc or remove them I can get the selector rod to engage and retain in gear either high or low gear effectively, but not both.

The gearbox had been rebuilt and there were three hand-cut gaskets. one each for the centre of the case halves and the two outer bearing covers. They were about 0.8mm each and I recall from your thread that OEM was a thin paper gasket. I suspected that might have contributed to too much float on the shaft effecting the dog engagement. I removed the gaskets and used gasket silicone but no luck.

Given the previous owner had gone to the trouble of machining a part to bypass the selector, and I've spent maybe 10 hours trying to align it I think it's more than operator error. Insufficient throw on the selector rod or the rebuild has put the gears or dogs slightly out of place such that the selector rod no longer gets the dogs to where they need to be.

I can select either low or high, but it involves removing the covers, a wrench, a bunch of shims and 5-10 minutes of farting around.

It spins freely by hand so I'm comfortable there is no binding and operates quietly. Had it it low and did maybe 5 minutes of cutting to break in a new blade and the motor died - very hot.

I'm not going to try and trouble shoot the motor. It's 74 years old. The VFD move just came earlier than I'd planned and, for now at least in a slightly different format. I've done all my speeds calcs and if/when I get the gearbox working properly the only extra cost of my current 'temporary' solution is a larger motor pulley.

I suspect I'll need to modify/rebuild/tweak the gear selector shaft to get a little more throw. That's a job for another day.

I'm borrowing your shop-air idea for the blower by the way. I like it.

 

[Johnjan]

I also have a 16" ML. The two speed shifter has a placard that says to shift only at low speed. I took that as the saw needs to be at the slowest blade speed per setting and shifted while the saw is running. That is how I've always done it and it's worked well, with no resultant problems.

 

[Hagatronics]

I also have a 16" ML. The two speed shifter has a placard that says to shift only at low speed. I took that as the saw needs to be at the slowest blade speed per setting and shifted while the saw is running. That is how I've always done it and it's worked well, with no resultant problems.

I tried it once - the speed dial has the same instructions on mine. It smashed the gears so hard ended up needing to TIG weld the input selector shaft back onto the selector fork.

I might try it again once I have the VFD in and try out the 'jog' function. But not anytime soon. It's safely in a gear and I ain't touching it!

 

[slowtwitch73]

I agree that it sounds like it could be normal operation. I change the gears on mine while rotating the wheels by hand.. more like a jiggle really. There is a collar on the shifting rod that runs between handle and box that does have a detent system on it.

 

[Skyking1992]

I have a DoAll and I shift from high to low and back while running. I always run the speed to the lowest setting and then do the shift. It is effortless and you can feel the gears engage. No noise or clashing.