Motor needed

[Gavj75]

So, I built a 2×72" beltsander and as I've had to build practically every single bit of it, as I've got no money to spend on it, I've had problems to solve every step of the way.

Anyway, it's finished now and looks great, I've even gave it a pretty tidy paint-job with my logo on the side.

The biggest problem I had was it kept throwing the belts but after I crowned my tracking and drive wheels using electrical  tape, again, it was problem solved.

So I used it for the first time last weekend and discovered that the 540W bench grinder motor which I built it around, doesn't have enough power. The belt slows down the second I put any pressure on it. I'm gutted.

So I need to do a re-build using a more powerful  motor.

Can anyone suggest where I can salvage a motor that will plug into the 240 socket(I have no idea with electrics) what will be up to the job please but keep in mind that I don't have much cash to spend.

Thankyou

[stevomiller]

You will want a 1 to 2 hp motor for most belt grinders, a true 3/4 hp will get you going if not pushed to hard.

Large shop wheel grinders, buffers (polishing lathes on your side of things), laudrymat size dryers and wash machines, an air compressor (perhaps find one the pump portion is dead, or the motor just needs new start capacitors), swimming pool and jacquzzi spa pump motors are 1.5 to 2hp usually. They tend to be nice sealed motors too that won’t short out from metal dust etc, and they are rated continuous duty. They replace pump with motor all the time. They are higher rpm, 3400-3800 rpm, just gear it down with pulleys.

Best

Steve

[Gavj75]

Thanks a bunch Steve. Hopefully I'll be able to sort something out from these options you've made me aware of.

Niv

 

[timgunn1962]

540W is 3/4 of a horsepower and is pretty weedy.

The general rule-of-thumb is 1 HP (750W) per inch (25mm) of belt width. 

As you've used a bench grinder as the basis for the build, I'm guessing the drive wheel is mounted directly to the grinder shaft?

If so, that's likely to be a source of cost if you change to a "real" motor.

Most bench grinders have plain shafts of 1/2" or 12mm diameter, one or two of 5/8" and one or two of 3/4". Motors you are likely to encounter will have either 24mm shafts (90-frame motors) or 19mm shafts (80-frame motors). You will need to adapt what you have to whatever new motor you come up with. The detail design of your current system is important, as it goes a long way to determining how easy or difficult the change will be. Pics would be good.

If the rest of the grinder is to a reasonably high standard (effectively permanent), I'd recommend going with a 90-frame 2-pole motor, which will most likely be 3HP. This is the biggest motor normally used for single-phase compressors and will run from a 13A UK domestic socket through a 13A fused plug. You'll need to check out your Consumer Unit(s) though. You may find the motor starting current trips the standard typeB breaker and that you need to change to a typeC. If you have old-school fusewire jobbies, you should be fine.

The IEC motor standards mean that you can swap out the single-phase 90-frame motor for a 3-phase 90-frame motor and VFD if/when you want to upgrade to variable speed in the future.

 

 

[Gavj75]

Hey Tim,

I'll take some pics of my sander so u can see what I'm ''playing'' with.

Although it would be a shame to take apart what I've built and start again around a real and appropriate motor, simply put, it has to be done. I'm sure I'll be able to salvage a lot of what I've got.

Gav

[MotoMike]

I too would love to see the pics Gav, so post them here.  I built my grinder as well and though I did buy the steel and wheels.  I had a 1.75 horse single phase 2 pole that came from my retired air compressor.  1.75 horse seems to do the job for me.  

this DIY belt grinder motor guide was most helpful to me.  if it doesn't survive check out dcknives.blogspot.com  and their DIY 2x72 build pages.  wealth of very specific knowledge. 

http://dcknives.blogspot.com/p/grinder-motors.html

good luck

 

[Gavj75]

Some pics Mike, thanks Gav

[Irondragon Forge ClayWorks]

On 10/6/2018 at 7:42 PM, Nivsknives said:

where I can salvage a motor

On this side of the pond, folks use salvaged treadmill motors. They can be had for free or really cheap, when people get tired of them. Don't know if they will work for you though.

[MotoMike]

Nice looking build.   Is it powder coated?

Air compressors are a good source I think.  

Good luck.  

[Gavj75]

I painted it with cans of spray. I gave it a good undercoat first then just built up the blue with multiple light coats in till I was happy.

Can u post some pics of your build please Mike?

Cheers , Gav

[MotoMike]

Sure Gav, but It's cave man compared to yours

[Gavj75]

I am very happy with how my sander looks Mike but it's not what's important really. Yours works properly and you can use it. At present , mine doesn't.

On a more positive note with regards to my sander, it's cost me very little to build so far. I'm a plater by trade so I have free access to most of the materials and equipment used to make it. I've had to buy the aluminium round-bar which a friend turned down and made my rollers/wheels with and I also bought the 8" bench grinder, which I thought would be ok to power it with - NOT. That's about it though and when I source an appropriate motor (a very kind Mr. Timgunn 1962 may be helping me with one), it should be up and working ok and I can put the 8" bench grinder back together and use it.

I reckon I've spent around £80 so far but £45 was on the bench grinder. 

I reckon I'm in the ''excellent value'' category as it stands.

Gav

[stevomiller]

A 3/4 hp is definitely on the low end. However, as I’m many know, there’s 3/4 hp motors and then there are 3/4 hp motors. Regardless of wattage/current/hp ratings (claims?) I’ve found many inexpensive tool’s motors to behave like they are perhaps 80% of what they claim or the motor plate lists. 

When scrounging motors (or especially if buying) for metal working tools I prefer TEFC to open drip proof or especially any open frame motor. Although open drip proof can run cooler you run the risk of abrasive and metallic dust getting inside and causing trouble, and non drip proof open frame motors can short out or get said dust into open or just shielded(not sealed) bearings.

OP, what size drive wheel is that you are using?

Temporarily you could drop the diameter on it so you won’t stall or bog it down quite so easy. Granted belt speed thus grinding speed is reduced, but you will be able to apply more pressure on your workpiece.

[Gavj75]

Hey Steveo,

My drive wheel is 5" .I've been on a steep learning curve  with this build so I'm guessing it's a bit big is it? What size would be right?

Cheers Gav

[stevomiller]

Gav your drive wheel would “probably “be fine with a 1.5hp motor.

Its a tough question on what to use since it’s a balancing act, and I haven’t actually used your machine. I’m guessing when working on wood, etc ,with lighter pressure , it does ok? Or is it that it doesn’t allow you to do any work at all?

if the first, then try reducing your drive wheel circumference by about 30%, if the latter your probably just out of luck.

BTW, what is the rpm rating of your motor, if you posted it I missed it sorry. 1200? 1500? 1800? 3600? Something else? Since your set up is direct drive your drive wheel size is much more important especially if your motor is smaller, because the available torque is much less.

[Irondragon Forge ClayWorks]

The motor is 3/4hp running at 2950rpm. https://www.iforgeiron.com/topic/54798-belt-tracking-problems/?tab=comments#comment-592598

A smaller drive wheel would probably help.

BTW, your grinder looks good to me just a little under powered.

[Gavj75]

I'd just like to say a huge thank you to everyone who has helped me out with these problems. This community of people are all helpful, kind and generous and I'm happy I discovered "I FORGE IRON"

A big thumbs-up to everyone