New workbench design thoughts and questions

r6_cannibal · Jul 12, 2011

Not sure if i should post this here or in the fabrication area, but anyway...
I'm building a new bench that I would like to last me for a long time.

some numbers real quick first...

the steel
2"x2" @ 1/4" thick = 5.410 pounds per foot
555.5 inches total material for frame = 46.3ft

46.3 * 5.410 = 250.483lb

125.2415lb per side

from the pipe to the contact point of the castors is 5 inches, with a 12" lever to rotate the mass should be about 52 pounds of force to lift the table.

would galvenaized pipe be able to withstand this type of rotational force?
I want to put a couple holes through the pipe and thread them to screw in the stem of the castor. I have this kind of setup on a small wood bench but the weight of this new metal bench is much greater.

I also wanted ideas on what I should put between the castor pipe and the hole cut into the leg of the bench. I was thinking a bushing of some type or another larger pipe that the castor pipe sits inside of and then grease the two friction surfaces so it rotates easily. I'm not really sure if i'm making myself clear here, the 1 year old kept me awake most of the night and we're out of coffee

I'm going with 2x2 square tube for the bench so i can insert a 1 1/2 inch square stock onto the top pieces that run the width of the bench. even the backsplash should be removable so i can have a nice unobstructed work surface when i need it.

the T-track isn't in it's final location, and there's going to be a removable piece in the center where a miter saw will sit flush with the bench, as well as a plate where an inverted router will sit for use as a router table. I'm open to ideas and suggestions of course! :beer:

Thanks in advance, I can't wait to get the design on this bench finalized so i can start building it.

chickenhauler · Jul 12, 2011

I used 1 1/4" galv. pipe inside a stub of 1.5" or so pipe with a grease fitting on my homemade lawn/road roller and it's held up ok and the roller weighs around 1500 pounds. Not sure if I'd go less than 3/4 inside 1" for your project. You could always get a rod and bushings from mcmaster carr too, I think they even have ratings on the rods.

chickenhauler · Jul 12, 2011

Nice drawing btw. I wish I knew how to do stuff like that. Looks like a well thought out bench too.

r6_cannibal · Jul 12, 2011

chickenhauler said:
Nice drawing btw. I wish I knew how to do stuff like that. Looks like a well thought out bench too.

Thanks! The program is called Google Sketchup, I just started using it a week ago. It's free as well, it was a little quirky to start with but i watched some tutorials on youtube and got the hang of it.

The external diameter of the pipe with the castors mounted to it is 1", i forgot to give that value when i created the thread.
That gives me more piece of mind if you have a similar setup for your roller of 1500 pounds. Have any pictures of it? It sounds pretty cool! I'll check out the rod and bushings as well. Appreciate the input :beer:

Jack Olsen · Jul 12, 2011

As a side note (and the drawing might just be a quick sketch), I would move the lever inboard under the bench and I wouldn't have the right axle extending out beyond the leg. You'll be bumping that stuff with your ankles more than you'll be using the casters.

The 2"x2"x1/4" tube is massive overkill. Which I approve of.

Wingnut65 · Jul 12, 2011

Nice Sketch-Up. Ive been wanting to learn and I'm impressed you have only a week under your belt.

Your that you are calculating are for the bench itself. Don't forget the load. There may be a time that you have an engine block or transmission on it and then realize you need to move it. Add a couple hundred for the moving weight and you should be fine.

chickenhauler · Jul 12, 2011

I have Google Sketch up, and I won't post the one pic I managed to make lol. Again, very well done

It's nothing fancy at all lol. I just stabbed a piece of 1 1/4" galv. pipe in the end when I had the concrete truck clean out the extras. It's 2 55 gal barrels welded together , and filled with concrete. Maybe 1500 was being a little conservative, but I doubt that it's over a ton.

For the "axle" I just welded a little collar on the inside, then my chunk of 1.5" pipe, then another collar on the outside. I drilled the 2" pipe for a grease fitting. I wouldn't take it on a cross country trip lol, but it works great for placing 2b limestone.

r6_cannibal · Jul 12, 2011

Jack Olsen said:
I would move the lever inboard under the bench
The 2"x2"x1/4" tube is massive overkill. Which I approve of.

I was going to type a response saying I wanted to put the lever under the bench but couldn't think of a way to do that without making use of the full width of the board that will be under the bench...and I realized I really don't need to make full use of the space under there. I'd much rather have the leavers tucked away under the bench, and I think I might know how to implement that now. Thanks!

Overkill is what I was going for. This will hopefully be my main bench for a long time, and I want it to survive through all my clumsiness

I saw your garage feature in Popular Mechanic, that's pretty awesome! congratulations

Wingnut65 said:
Don't forget the load. Add a couple hundred for the moving weight and you should be fine.

That's a really good point. The castors are rated at 480lb total (120lb each) and given that the support for the frame alone weighs 250lb...I should probably not go cheap on the castors. throw in the top, some equipment where another sheet of MDF will be on the bottom, attach the vise and that'll easy be over the load rating for the current castors if i put a short block or trans on it. I'm going to put a metal top on it way down the line, I hadn't planned ahead for that in the castors. Thanks! :bowdown:

chickenhauler said:
Maybe 1500 was being a little conservative, but I doubt that it's over a ton.

Man that's crazy! A whole lot of weight for a couple of pieces of pipe, that's nice a simple solution has worked out so well. Thanks for the picture :thumbup:

Brad54 · Jul 13, 2011

Maybe you could go with just two casters--steel wheels--at one end, and use a floor jack at the other end to move it around. Are you planning on moving it often, or "just in case I want to some time"?

Making it with the plan of a floor jack at one end would save some time and money, at the expense of a little extra hassle when/if you move it.

The other solution might be to get really strong casters and have them permanently fixed to the bottom of the legs, and then lock the table in place with Floor Locks, like these from McMaster-Carr.

http://www.mcmaster.com/#floor-locks/=d5i5bt

The feet keep the table locked in place, and then to move the table, you just release the locks.

If you have two fixed wheels at one end, and two swiveling wheels at the other, I don't see why you'd need more than one floor lock between the swiveling feet, though you might feel better if you had one at both ends.

-Brad

r6_cannibal · Jul 13, 2011

Brad54 said:
Maybe you could go with just two casters--steel wheels--at one end, and use a floor jack at the other end to move it around. Are you planning on moving it often, or "just in case I want to some time"?
-Brad

I'm still on the fence about going with heavy duity castors. The floor locks are what got me started on the lifting castor path. I like the floor locks but they're spendy. Double locking castors might still be an option.

The bench will move a lot. I like the Jack idea but not for this particular bench

-edit-
my phone ate part of my post, strange.
part of the reason i didn't like the floor locks is that they don't seem to be rated laterally or at all for that matter. I'd just feel better having the table on all four legs when bending pipe or prying something in the vise

buening · Jul 13, 2011

The yield stress for Schedule 40 steel pipe is 35ksi. Allowable torsional shear stress is 0.6 times that, so 21ksi = 21,000psi. Actual shear stress = Torsion * radius/J. J is the polar second moment. With a lever of 12" and force of 52lbs, you get a torsion of 624 in-lbs. Lets use 3/4" Sch 40 steel pipe. The J for that pipe is 0.07 in^4. That was pulled from a table. With that info, we get actual shear stress of 624*0.75/0.07 = 6686 psi. Using 1/2" pipe, you have a J = 0.032 in^4. That results in a shear stress of 14,625psi. For factor of safety and fatigue, the minimum I'd use is 3/4". Pipe doesn't handle fatigue the best. If you are really worried about it, get some solid round bar and be done with it

ludakris04 · Jul 13, 2011

buening said:
The yield stress for Schedule 40 steel pipe is 35ksi. Allowable torsional shear stress is 0.6 times that, so 21ksi = 21,000psi. Actual shear stress = Torsion * radius/J. J is the polar second moment. With a lever of 12" and force of 52lbs, you get a torsion of 624 in-lbs. Lets use 3/4" Sch 40 steel pipe. The J for that pipe is 0.07 in^4. That was pulled from a table. With that info, we get actual shear stress of 624*0.75/0.07 = 6686 psi. Using 1/2" pipe, you have a J = 0.032 in^4. That results in a shear stress of 14,625psi. For factor of safety and fatigue, the minimum I'd use is 3/4". Pipe doesn't handle fatigue the best. If you are really worried about it, get some solid round bar and be done with it

I should have studied better in school. It looks so easy when a pro writes it out.

buening · Jul 13, 2011

LOL, well I have to admit I don't do too much with torsion in my daily job (bridge designer)....so I had to pull out the old textbooks for a refresher course

r6_cannibal · Jul 13, 2011

buening said:
The yield stress for Schedule 40 steel pipe is 35ksi. Allowable torsional shear stress is 0.6 times that, so 21ksi = 21,000psi. Actual shear stress = Torsion * radius/J. J is the polar second moment. With a lever of 12" and force of 52lbs, you get a torsion of 624 in-lbs. Lets use 3/4" Sch 40 steel pipe. The J for that pipe is 0.07 in^4. That was pulled from a table. With that info, we get actual shear stress of 624*0.75/0.07 = 6686 psi. Using 1/2" pipe, you have a J = 0.032 in^4. That results in a shear stress of 14,625psi. For factor of safety and fatigue, the minimum I'd use is 3/4". Pipe doesn't handle fatigue the best. If you are really worried about it, get some solid round bar and be done with it

Awesome, thanks! Thanks for the quick write up too, I never would have been able to find that on my own but is exactly what I was looking for :beer:

chickenhauler · Jul 13, 2011

chickenhauler said:
Not sure if I'd go less than 3/4 inside 1" for your project. You could always get a rod and bushings from mcmaster carr too...

Sometimes I get it right without a fancy edjumacashun :rocker:

buening · Jul 13, 2011

Hey no problem, glad to help! Nice job on that Sketchup. I'm gonna have to learn to use that, thats pretty slick for renderings!

Jack Olsen · Jul 13, 2011

A couple of other thoughts:

1) the lower (horizontal) gussets seem unnecessary to me. Assuming this is welded 1/4"-wall steel, I can't think of much torsional stress being directed their way. I would think the crossmembers themselves would be plenty.

2) If you want overkill, why not make the rear gussets go from the lower crossmembers to the top ones -- like an M shape along the back side of the bench.

3) The nesting tubing idea is great, but most off-the-shelf 2"x2"x1/4" square tubing will not accommodate 1-1/2"x1-1/2" tubing because of the seam inside it. You can buy tubing designed for this use, which is seamless, but it's more expensive.

All that said, bear in mind that I am in no way, shape or form anything like an engineer. The only physics class I ever took was called 'Physics for Poets.' :headscrat

buening · Jul 13, 2011

I agree, in fact any of the diagonal gussets/braces is pretty much overkill. You could save yourself some headaches and remove the gusset braces. A smaller scale way of doing it is to weld plate gussets instead of tubing. The workbench I just built (but have yet painted so no pics) is also 2"x2"x1/4" and I have no gussets. If you weld continuously around the joints of the legs to horizontal top tubes there will be enough strength there to handle what you want. I flipped my bench upside down and with my foot against one leg I pushed on the other leg with all the strength I had to see if it would move and it wouldn't budge. You likely won't see 200 or 300lbs of lateral kickout force on one leg, so I wouldn't bother with gussets.

If you have a long die grinder bit or by using a file you can remove the bead from inside your 2x2" tubing. I chose to buy the 2"-to-1.5" hitch adapters from Walmart, cut the 1.5" stub part off, and then welded the 2" part into the upper corners of where the legs meet the top horizontal tube. Its exactly like a receiver but without all the other plates and **** on it. Food for thought..

dittle fart around · Jul 13, 2011

View media item 10148Here's my workbench made of 2X2 tubing. I laid the top outside of the legs to get more surface to weld. The back brace is 1 1/2 X 1 1/2 but the tubing wall is at least twice as thick. Don't have the specs, the tubing is recycled soccer goals.

r6_cannibal · Jul 13, 2011

Jack Olsen said:
A couple of other thoughts:

the lower (horizontal) gussets seem unnecessary to me.

That's a good point, It'll be a lot less time spent on the bench too if they're not needed.

The nesting tubing idea is great, but most off-the-shelf 2"x2"x1/4" square tubing will not accommodate 1-1/2"x1-1/2" tubing because of the seam inside it.

I was planning on taking down the bead inside the tubing to make it fit together, good looking out

r6_cannibal · Jul 13, 2011

buening said:
If you have a long die grinder bit or by using a file you can remove the bead from inside your 2x2" tubing. I chose to buy the 2"-to-1.5" hitch adapters from Walmart, cut the 1.5" stub part off, and then welded the 2" part into the upper corners of where the legs meet the top horizontal tube. Its exactly like a receiver but without all the other plates and **** on it. Food for thought..

Ditching the gussets will save me some time and stock, thanks!

I'll take a look at those adapters, actually going to walmart today so that works out pretty good. I go there about once every 6 months so that was excellent timing!

r6_cannibal · Jul 13, 2011

dittle fart around said:
Here's my workbench made of 2X2 tubing. I laid the top outside of the legs to get more surface to weld. The back brace is 1 1/2 X 1 1/2 but the tubing wall is at least twice as thick. Don't have the specs, the tubing is recycled soccer goals.

Good looking bench! I'm checking craigslist for pallet racking or any kind of steel i can find at a good price for other projects, i'll definitely add soccer goals to my saved search! I usually prefer to re-purpose existing items rather than buying new stock. yeah it's good for the environment and all that stuff, but it's also less expensive :thumbup:

How are the locking castors working out for you? is there any play or wiggle on the table when they're locked down?

New workbench design thoughts and questions

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