Startrite bandsaw

cletus

I have a Startrite Bandit vertical bandsaw, similar to the one in the picture. The issue I'm having is that it blows the plug fuse maybe every 5th time of starting, on average. This was an issue for the previous owner also, but as I got it for a favourable price, I thought it would be worth trying to repair.

Along with the on/off switch on the box at the side, there is a key at the rear, with both obviuosly needing to be turned on to operate.

My initial idea was to bypass the box, using only the key to turn on, and as it wont be used in a comercial setting, I'm not too concerned about losing the safety off switch.

Befor I begin, however, I'd like to get the opinion of the hive mind here, or perhaps even find a grizzled old veteran who can say "I worked with one for years, your problem is..."

If this isnt the best forum, please feel free to mve, mods.

Steve

Can you post a pic of the motor rating plate? Or post what it says?

It might need a 16A supply or larger. It's possible the previous owner put the 13A plug on it not knowing this.

cletus

Plate is stamped, but hard to read. Ive rubbed some pencil lead on to try and get it to show up. Amp is stamped 6.0. Maybe it should be 16.0?

Steve

Its hard to see alright.

The figures don't add up.

It looks like 6.0 A alright but it also looks like 3HP would mean about 17-18A full load.

6 amps would be typical for 550W 3/4 HP motor, it will however pull about 40 Amps on startup for a few milliseconds. This may or may not blow the fuse which could be what you are seeing.

If you have access to a grip-on ammeter, best bet is to measure it when you get it running.

Edit, also be aware that motors are always overrated and so generally never pull full load current.

cletus

Trying to get a loan of a clamp meter at the moment, but in the meantime, a few questions. According to the previous owner, it was always on a 13 amp fuse, and this was a problem that developed later on. Can I assume, then, that it is more likely to be a short somewhere in the system, or is it a case that the 13 amp fuse, being rated, probably, for higher than the nominal value, is being weakened by a number of starts, then eventualy gives up the ghost.

Also, given that it also only ever blows on startup, can I assume that it is the initial inrush of current, due to a lack of soft startup, is causing the fuse to blow rather than the normal operating current. If this is the case, could I hypothetically install, say a 16 amp fuse in the plug, to get over the initial spike.

Calahonda52

What rating is on the electrical starting box?

It may be over sized.
I have a similar saw and I have a motor starter mcb on the sub distribution board which takes care of the initial surge: the plug is the blue 16Amp

It might also be worth blowing out any dust that might be in the casing

cletus

So had a look at the electrical box, it says the rating are on the inside, but thres nothing. I've uploaded some internal pics.

There is som sort of slider on the bottom right with a series of numbers. Anybody shed light?

Calahonda52

Its an overload protection relay which looks to be set at the max, i.e. above 6A
No details inside on back of cover?

Steve

cletus wrote: »

Trying to get a loan of a clamp meter at the moment, but in the meantime, a few questions. According to the previous owner, it was always on a 13 amp fuse, and this was a problem that developed later on. Can I assume, then, that it is more likely to be a short somewhere in the system, or is it a case that the 13 amp fuse, being rated, probably, for higher than the nominal value, is being weakened by a number of starts, then eventualy gives up the ghost.

Fuses don't work like that, if it was a short then it would blow every time.

The next thing I'd do is take the band off and check all the bearings. Higher resistance to movement means a higher starting current.

It could also be the starting capacitor, that will be harder to diagnose over the internet.

Also, given that it also only ever blows on startup, can I assume that it is the initial inrush of current, due to a lack of soft startup, is causing the fuse to blow rather than the normal operating current. If this is the case, could I hypothetically install, say a 16 amp fuse in the plug, to get over the initial spike.

You can't put a 16A fuse in a 13A plug even if you could find one. It would also be dangerous and risk a fire.

See what happens if you can get an amp reading and I can advise further.

cletus

Thanks Steve and Calahonda. I'll try get an amp reading. There is no info on the back of the electrical start box.

Odelay

How long is the lead going to the plug?

cletus

About 6 or 7 foot. However, in my shed I have no power, so I was running it on an extension lead of about 25'

Odelay

cletus wrote: »

About 6 or 7 foot. However, in my shed I have no power, so I was running it on an extension lead of about 25'

Where is the fuse blowing?

cletus

Plug top fuse of the machine itself, regardless of being plugged directly into the wall or into an extension lead

cletus

All right lads, it took three weeks, but I've got hold of a clamp meter.

So its consistently drawing 40amps at start up, dropping off to about 3.5 almost immediately. It might do 3, 4 or 5 starts before blowing the fuse, or it might do one and blow it on the next start.

Interestingly, it blows the fuse of the short extension lead I'm using as a line separator for the ammeter.

So in summation, it blows fuses at the plug top of the machine when plugged into a 25 extension lead, but blows them at the plug top of a 2' line separator when that is plugged between extension and machine.

While I wait for further instruction from wiser heads here, I think I'll take off the motor cover, band cover etc, and blow out whatever sawdust and general crap that has built up over the last 25 years

M.T.D

Assuming the motor and capacitor are ok would something like this help.
Called a soft start. limits initial current
http://ie.rs-online.com/web/p/soft-starts/3305358/

cletus

Thanks mtd, was thinking of something like that, but I'd like to see if I can solve the problem first. If clearing the saw dust and general crud doesn't solve the problem, I'm going to look at the capacitor next.

Having read up a little on inrush currents, it would seem that anything from 4-8 times the rated current is acceptable, so given that the rating is for 6 amps, the inrush is just over 6.5 times that, so would I be right in assuming that the 13 amp fuse should be adequate?

jca

What's the current draw without a blade? Maybe the blade is over tensioned.

Odelay

Have you tried starting it a couple of times with the band removed? Also is there a brake on the motor? How does the saw stop, in a few seconds or run down slowly?

cletus

Haven't tried with blade off, will give it a spin and report back. No brake, runs down slowly

cletus

Ran the saw with no blade, inrush was between 34 and 39 amps. Started multiple times, did not blow a fuse.

Replaced the blade. The tension indicator is in 1/4's, so it runs 1/4, 3/8, and I presume the next number is 1/2. It had been set at 1/4. When you release the blade, the dial runs back to a dot, or .

I adjusted the tension to about halfway between the dot and 1/4, fuse blew first time. Then I ran out of fuses

Odelay

cletus wrote: »

Ran the saw with no blade, inrush was between 34 and 39 amps. Started multiple times, did not blow a fuse.

Replaced the blade. The tension indicator is in 1/4's, so it runs 1/4, 3/8, and I presume the next number is 1/2. It had been set at 1/4. When you release the blade, the dial runs back to a dot, or .

I adjusted the tension to about halfway between the dot and 1/4, fuse blew first time. Then I ran out of fuses

What are the guide bearing ls like for the blade? Especially the back bearing? Is it scored?

cletus

Are you taking about the bearings that run the guide wheels in the pictures below? If so, I haven't taken those wheels off so can't comment. I can do that next if you think it may be the issue

cletus

Sorry pics are here

cletus

Sorry pics are here

Odelay

cletus wrote: »

Sorry pics are here

Hard to tell from the photo but the back bearing doesn't look great, is it worn away? Can't link now but it you google them you will see that the back bearing should be in good order and free running. Can you take a photo of it more to the right side of the blade?

cletus

Is this what you're looking for? The wheel spins freely, bit of wear on the rubber where the blade sits, it turns freely even with the blade on and tensioned

cletus

Just noticed picture didn't attach

Odelay

cletus wrote: »

Is this what you're looking for? The wheel spins freely, bit of wear on the rubber where the blade sits, it turns freely even with the blade on and tensioned

No, trying to include a pic but it's not happening. It's the bearing/wheel that is at the back of the band saw blade. It is behind the guides directly above the piece as it's sawn. This should turn freely while sawing/running. Unless it is very bad, it would only cause a problem while cutting. However, if it is terrible and not adjusted right it could cause extra load on start up.
Is there a drive belt from the motor to the bottom wheel? There should be and most of these can run at a higher/lower speed. Does yours go from a big pulley to small or small to big? There should be a choice of two speeds.

cletus

Ah right, get you now. I've attached a picture minus the guard. The bearing spins freely. There is never an issue with the fuse blowing once the saw has started. It doesn't blow mid cut or anything

cletus

Re the driven wheel. I've also attached a picture of the entire internals. There is only one speed, and it would appear that the driven wheel runs directly of the motor

Odelay

cletus wrote: »

Re the driven wheel. I've also attached a picture of the entire internals. There is only one speed, and it would appear that the driven wheel runs directly of the motor

A direct drive is very unusual for bandsaws in my experience.
If it starts fine without the blade on the only other thing I can suggest is opening the guide assembly so it is 5mm away from the blade and trying to a few starts without cutting and see if it reliably starts then.
If it still trips with the guide opened then I'm all out of ideas buddy:(