Home made belt sander power supply.

[Des333]

Having constructed a prototype of a belt sander from bits and pieces and part of a old linisher I need a power supply. Looking at some similar projects a !/2 hp motor is suggested or better a 1 hp for more power, I need some help with the power supply has anybody constructed something like this and what motor did you use. Various electric motors are available, washer machine etc. but what would be the better motor and how could I control the speed? I have one V belt pulley and would prefer an alternative speed control rather than swapping the belt on various pulley's. Any suggestions and information gratefully appreciated.

 

[glynster]

I haven't built one myself but it's on my to do list but having built my own CNC I feel a bit more at ease with engineering and electronics than I did. Firstly, I think you are talking about a motor and not a power supply - you really would only need a power supply to run a DC motor, an ac motor will run off the mains. You need a low speed motor - the average standard equip ac motor will be too fast - you can of course gear it down with pulleys but generally its better to get a motor at the correct speed - 1300 to 1700 rpm range. Also you will need to take into account what kind of mount you will require to fix your motor to your machine frame - this will depend on your design and it will bear a lot of sheer force so needs to be solid, a foot mount or a flange mount is common - you can get some that do both. Expect to pay over £100 for a new 1/2hp to 1hp motor. I think 1/2hp (320w) is underpowered personally - chances are your motor will outlive your machine and can be repurposed later for other machines or a rebuild so get a good one. BTW, there is really no such thing as a variable speed AC motor (not by varying voltage anyway). Of course you CAN vary the speed of a AC motor using a variable frequency drive (no that's not the same as a flux capacitor ) but thats getting expensive and they are complex to configure to the motor or they will trash your motor instantly - trust me I learnt this the hard way.

The simple and tried and tested solution is to use the motor and speed control from an home fitness treadmill. 99% of people who spend £400 to a grand on one only use it for a week and then hang their clothes on it for 2 years so they come onto ebay all the time for £50 and you will find one locally I bet. From this, you can glean a perfectly suited, well powered motor, with speed control, pulleys, steel rollers, quality bearings and even a perfect flatbed - google for treadmill flatbed sander, its been done many times. Otherwise, you should consider using a DC motor which can be variable speed simply by changing its voltage - something like this will control it very well - it also acts as a rectifier https://www.amazon.co.uk/gp/product/B00 ... UTF8&psc=1

Be sure to match the speed controller voltage to the DC motor voltage if you follow this route. The downside of this approach is that DC motor in the 1hp range are expensive and finding one to match the voltage of the speed controller might be tricky.

I'd go with the AC motor - buy an old treadmill and knick its innards and gubbins and I'd also utilise the digital control panel. Hope that has helped and not confused you - I'd like to see what you have done and do as I plan on doing the same when I get the time.

 

[glynster]

PS; goes without saying but be sure to earth any metal parts or chassis and use and RCD - even if you have to use an inline one. Makes the difference between a quick shout out to the almighty and meeting Him in person.

 

[Monkey Mark]

Mostly as above really.

I'd avoid induction motors as they are more difficult /expensive to control the speed.
Dc motors are easy for speed control.
Ac are also easy using PWM speed control (there's a newer mire efficient method too but i can't think of its initials right now).
As for washing machine motors, just avoid. Unless you have the control board from the washer too they are no good. Yes you can run them, but in what they call suicide mode as it continues to speed up until self destruction due to thermal runaway.

Also, what size will the surface area be? If it's small then 1/2 hp might be ok but the bigger the potential surface area the greater the friction.

You could always use a 3 phase motor with a little modification. They always sell real cheap on ebay as most people don't want them. Definitely more bang for your buck.

 

[Des333]

Thanks to Glynster and Monkey Mark for the information and advise very helpful. Following your in Glynster I'm rethinking the rig, I never thought of using a treadmill. Having started looking at motors, not power supply, you're right it can be expensive and a bit of a minefield. I have found an old portable compressor (Sprayit model with a motor) so I'm thinking of using the motor. Also going to look for a treadmill although space is a bit of an issue and only really need bench top sort of size but with better motor/quieter than a hand sand clamped to the bench. Thanks for your help.

 

[woodpig]

My BDS250 has a 1 HP motor. You don't need speed control, standard 1450 rpm is fine.

 

[glynster]

I meant buying the treadmill purely to pillage its motor and any other mechanisms or electronics you might need - you could pick one up on a Saturday, rip out its motor and have it at the tip late that day. In fact, these days, you could leave it at the end of your drive and the scrap monkeys would whip it away in a day or 2. A decent motor will set you back £150 - you can get a barely used treadmill for £50 or often much less - some people are sick and tired of them using up space in their garage and would almost pay you to take them away. Check ebay - there's people starting them at 99p and because they cant be easily delivered they get no bids, especially if they have gone a bit rusty.

BTW Stumpy Nubs plans for a belt sander are one of the best I have seen https://www.youtube.com/watch?v=tUJiOBU ... StumpyNubs

He sells the plans for a few dollars but you'd be better buying his book for a few quid more as it has all of his machine and jig plans in it for one price https://www.amazon.co.uk/Homemade-Works ... tumpy+nubs

 

[Des333]

Thanks Glynster for the follow up and the link to Stumpy nubs, certainly a well made piece of kit and the top sanding feature is a nice touch. I did get your drift of using the bits from the treadmill and I'll have a look for a cheap one to get the motor and other bits, Gumtree might have one local.
Appreciate your input and comments, thanks.

 

[Des333]

Thanks Woodpig, I did like the idea of speed control but I think your right it's not necessary if the motor is right, I'm going to check the Sprayit compressor and possibly use the motor if the speed is correct. I've got a lot more information now so thanks.

 

[Monkey Mark]

He sells the plans for a few dollars but you'd be better buying his book for a few quid more as it has all of his machine and jig plans in it for one price https://www.amazon.co.uk/Homemade-Works ... tumpy+nubs

Great shout on the plams. Didn't realise he had a book so may just have to treat myself.

 

[woodpig]

Thanks Woodpig, I did like the idea of speed control but I think your right it's not necessary if the motor is right, I'm going to check the Sprayit compressor and possibly use the motor if the speed is correct. I've got a lot more information now so thanks.

We had several where I use to work. Some of them were used exclusively for metal, others for wood and plastics and none of them had speed control.