Engineering Question

[Cheese]

We are hosting a logging competition here, I am way behind on sleep among other things, but I have a problem.

We need to make 4 vertical chopping stands. Problem is the guy in charge made an oops and we need to fix it cheaply, quickly and easily.

I have a plate that is 11" square. It holds logs up to 11" in diameter with spikes that engage approximately 2" of wood and stand 4" off the table.

He envisioned butt welding these 4 towers, one into each corner of the plate, and then running the screw through them into the wood. Based on the horse power I generate, I am pretty sure I am going to take those SOB's right off. How would you do it?

Here is a pic of the stand. The log is standing on the plate where I need to attach these towers. I will be back to explain if this doesn't make sense. No, that isn't me in the pics, big props if you know who it is though.

http://pics.montypics.com/flygtenstein/2007-10-16/1192584724_vertical_stand_4.jpg

[AxleIke]

To be clear, the picture is of a working stand, one which you would like to emulate?

Also, what diameter screw are we talking about?

I agree that 2" will likely not do the trick. nor will a narrow screw, like a deck screw.

With a long, roughly 5 inch long screw, between a half and 3/4" diamter, mounted in 4 places, I believe you could secure the log. Obviously this would involve drilling, and I'm not sure if you have that kind of time during the competition.

Better than screws would be to run two bolts clear through, at different heights, with one tower a through hole, the other a welded nut. Again, drilling required.

Looking at the above picture, using the current design with screws used like spikes, if you can apply pressure somehow to the opposite end of the tower, where it hangs down, and instead of welding the towers, allow them to pivot via a bolt, you could hold the log. A ratchet type strap could accomplish this fairly easily. It might look fruity though, not sure if that would fly.

[Cheese]

Bad explanation.

In the picture, four hinged spikes drive into the log to hold it.

I have 4 towers that have to be mounted on top of the plate because of a design flaw, in hopes of emulating the functional stand in the picture.

Through the little towers will be likely 1/2" diameter bolts that will penetrate about 2" into the wood.

I am asking if anyone can see a better way than the towers in the corners.

[AxleIke]

I understand.

No hope of hinging them at the corners with some scrap steel, and making it similar to the proper one?

What are the towers? Tube, angle, strap?

Sorry I'm not more help, not seeing the reasons it can't work. Hopefully someone else will chime in.

BTT

[Robinhood4x4]

What's the first rule of building a cage? Triangulation!

If I'm understanding things correctly, the towers are not like the ones hinged things in the pic, but rather they are just square tube or similar, butt welded straight to the plate. The towers have a hole drilled in them and a big screw goes through it and into the wood. You are afraid the butt welds will give.

If your stand is otherwise similar to the one in the pic, weld the towers to the side of the frame, rather than the top of the plate. To make it even stronger, extend the towers downward until they meet up with the crossbars underneath (hence the triangulation remark).

Keep in mind though, that the screws will not be normal to the surface of the log unless you shim the towers so that one of the faces is pointed toward the center of the stand.

If I'm off, describe the what the towers are, like Ike said.

[Erich_870]

:pics:

I don't know if I understand either. Post a pic of what you've got. :)
Erich

[Cheese]

There is a pic.

Imagine a table, 11" square and flat.

The table has to reliably hold up to an 11" diameter log vertically. While holding the log, it will be violently pummeled with an axe until the top half comes off.

We need to construct a method for securely holding the log to the table.

The current proposal is a 4" high tower in each corner with bolts that screw in from the corners theoretically converging at the center of the log but actually only making about 2" of penetration into the log.

I am worried the towers being welded to the top of the plate will be weak. It is almost impossible to tie the towers to eachother since that is about where an axe needs to swing.

Don't make me get out MS Paint!

[04 Rocko Taco]

This explanation made it for me, like a christmas tree stand. I got it now...

when you weld the towers to the table top, is there anyway a long bolt could run through the towers top to bottom, and bolt through the tabletop? I dont know that having them bolted + welded gives it any more strength, but its an idea....otherwise, you need a 16" table top, to hold an 11" log, and build the towers just like you have them, only you can put in bracing to the 11" mark, so an 11" log still fits inside the angled bracing, and then just use longer bolts in the tower to make up for the fact that they are further back.

[Erich_870]

:hillbill:

I get it now.  Put your paint brush away  :flipoff:

First thing I'd do is upgrade the bolts so they penetrate further.  You have a much better feel for the forces a big guy with an axe can create, but if 2" isn't enough, double or triple it.

Secondly, what about creating an "X" on the bottom of the 11" plate with 1 1/2 or 2" square tube that is welded so there is more surface area to weld the towers too.  It would give you the thickness of the plate PLUS the depth of the square tubing.  I know your looking for fast and cheap and I don't know what resources you have. 

I agree that just welding a tower to the side of a plate doesn't sound strong enough.

Am I any where on the map with this idea?  :screwy:

<Clarification> My idea is to run your towers on the OUTSIDE of the plate and that the tube "X" would effectively deepen your plate and tie all 4 towers together. I just wanted to make that distinction <Clarification>

Erich

[Texas Jim]

Sorry don't know who guy is, but I think an easy solve to your problem is to add 4 gusset-ts to the bottom of the 11 inch plate, all at opposite angels to the towers. Also go to a stove or lag bolt of at least 5/16's or bigger... TJ