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42 inch grinder design


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a small suggestion here, bearing in mind that a horse racing buggy and a donkey cart are in principal the same yet there are some differences other that the "motor" :D the USA is full of knowledgeable and mostly friendly and helpful folk like Steve (mostly friendly mentioned for your benefit:P) take the time to get to know one or two and put in the effort to go and visit(I managed it all the way from Africa) and try out and look at their kit before you build your own ! knowing where you are heading will seriously assist in finding  out what you need/want in a chariot/cart type of thing.   while there may be many ways to skin a cat your approach may vary depending on weather that "cat"is a local tabby or a Bengal tiger.

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I have built a wooden belt grinder and it works. It isn't perfect but it does work.  https://www.iforgeiron.com/topic/49875-diy-2x72-belt-grinder-plywood/
My biggest issue is the size and weight.  It takes a lot of wood to make it sturdy.  What could easily be accomplished with a couple of  2" pieces of heavy wall box tube requires several layers of 3/4" plywood to get similar rigidity.   If I had it to do again, I wouldn't go the wood route.

Also consider 80/20 aluminum extrusion.  A quick google search (search for  '8020 belt grinder') shows several DIY grinders built using the 80/20 extrusion.  I've worked with 80/20 and it is almost as easy to build with as wood and in the end the materials cost is probably quite similar.  80/20 surplus is also available on eBay for reasonable prices.

There are a variety of wheels (glass reinforced nylon and steel) available at reasonable prices on eBay.  I used the glass filled nylon ones and haven't had any problems. I considered making my own wheels.  After pricing bearings, other materials, and the time and effort required, it was cheaper to just buy them.  Ultimately the wheels I purchased were better than anything I could have made for the same cost.

For belt tension I am using a gas spring/strut like the ones on the trunk of a car.  I started off with a 20lb one and it was too weak and my belt slipped a fair amount.  I recently upgraded to a 40lb gas spring and it eliminated the belt slippage.

I'm using a 1-1/2 hp motor.  It does a decent job but I can bog it down if I really try to. I don't think a 1/2hp motor will be useful for anything other than just watching the belt go around. 


Edit to add:
Check and see if you have a welding school near you.  The one my daughter is going to will take on projects for people at very reasonable costs.

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19 hours ago, Irondragon Forge & Clay said:

What are you planning to use for the belt tension? Didn't see anything in the diagram.

I was planning on using the motor mount be adjustable via tracks nuts and bolts, it would also be the way to change out belts. Depending on what I need for tension I need I may attach a compression spring to a wheel if the motor mount adjustment is not enough.

 

18 hours ago, RogueGeek said:

I'm using a 1-1/2 hp motor.  It does a decent job but I can bog it down if I really try to. I don't think a 1/2hp motor will be useful for anything other than just watching the belt go around. 


Edit to add:
Check and see if you have a welding school near you.  The one my daughter is going to will take on projects for people at very reasonable costs.

I will be using a 1 1/2 hp motor, I have since revised a few factors since posting the design.

Unfortunately the welding school near me has bad times of their classes and they are more than I can spend. I am trying to keep costs down by making things with what I have.

 

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5 hours ago, Brian Evans said:

I was planning on using the motor mount be adjustable via tracks nuts and bolts, it would also be the way to change out belts. Depending on what I need for tension I need I may attach a compression spring to a wheel if the motor mount adjustment is not enough.

Consider the how often you will need/want to change belts.  With most of the existing grinder designs you can change a belt in just a few seconds. Adjusting belt tension via the motor mount will probably get old very fast.

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8 hours ago, RogueGeek said:

Adjusting belt tension via the motor mount will probably get old very fast.

Especially when your working your way down through the grits. Done with 220? Belt change. Done with 320? Belt change. Done with 440?... Imagine doing that all the way down to 1000 grit. You get the idea. 

Having it be fast and simple will save a lot of time and headache. 

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  • 2 weeks later...
  • 11 months later...
On 11/2/2017 at 9:14 PM, Brian Evans said:

Ok I am getting a better idea of what I should be looking for when I am building it. I may end up adding a three step pulley to the design later if I need to. For now I want something that doesn't take as long as a hand file. I am going to have my drive wheel 5 and a half inches in diameter.

Pardon my 1 year later question, but when you put in a step pulley, you have to be able to track it side to side right, so that you can line things up closely? 

Its not like the chain on a bicycle that can just be off to the side a little as you change gears, right? 

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I used 2 identical step pulleys mounted so that the sizes of the steps were opposite each other; the smallest step on one was lined up with the largest step on the other one similar to the configuration used on some drill presses.  That way the belt length needed is always the same and the corresponding pulleys are always in line with each other.

But yes, you do want the pulleys lined up.  If they are off by much the pulleys may try to wander on the shaft when in use, and of course if they are too far off it could throw the belt.

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