Thursday, 19 May 2011

I Know Jack About This Stuff...

In the last post I tentatively put the thought out there about building hollow workbench legs and filling them with sand for added weight. I dreamed up this brainwave because I want the bench I am going to build to be the perfect boat anchor. Making an 8, 10 or 12-foot bench heavy enough appears to be an easy task if you can afford the right timbers. The one I want to build will only be 5-feet long or less, so I think even if I could build it from ironwood, I’d still be chasing it around the room (ironwood often weighs more than 90-pounds per board foot).

The great part about blogging is how quickly things can happen. It didn’t take longer than two hours after posting that article before I realized I was on to something. Ok, the downside of it all is that my original brainwave turned out to be about as original as green grass, but at least I knew it is going to work.

I got a few comments posted here, plus a few more emails and they all said the same thing; “been there – done that – love it!”

Out of all the responses I got, only one used sand; Stoner told me he built a covered tray under his bench and filled it with four bags of sand. By my calculations, he added a quick 360-pounds to the weight to the bench for, what? fifty bucks?

Damlen in Belgium used gravel to fill his hollow workbench structure. He also suggested a possible negative to using sand, mentioning that it may possibly seep through the joints. It was good of him to mention this as I hadn’t thought too much about it, but will now that he warned me of the possibility.

Others emailed to say they filled their structures with scrap metal, stones, bricks and other sundry material that they recycled into ballast. It all was useful information for me and I thank you for it.

Now that all of you have confirmed to me that I am on the right track, it is time to take the idea and run with it. Ok, maybe not run with it, but at least be able to move it around a bit.

A while ago Chris Schwarz posted about Floor Truck Locks, an odd name for something that jacks a wheeled item up so its casters no longer touch the floor. The ones Chris discussed are available from the CasterStore.com for thirty bucks a pop.


Here’s the rub; with all that weight in each leg, anything that will jack it off the floor needs to be right under each one, preferably centered. Putting these in that position will make it impossible to activate the foot petal. Modifying them will result in a boom, rather than a foot petal, so these wonderful little items just aren’t going to work of me.

Enter my next brainwave.

Now I would like to think this is just pure genius in motion, but the reality is, the idea I have is based on the same concept as the adjuster I designed for the Birds House for the Shooting Board. Even that wasn’t an original concept as it is based on the same technology we all have used for years to change a flat tire – the scissor car jack.

Here’s the idea…

I would rather see the solid wood of the leg resting on the floor than have that leg swinging from a jack so this concept reverses things, putting the caster on the lift and letting the foot of the leg take the weight when it isn’t being moved.

Making a square scissor jack that just fits into the base of the leg will allow the leg’s structure to help keep the caster from twisting in ways I would rather not see it twist.

The casters only need to retract about an inch, so the lift capacity of the scissor jack needn’t be much. This means the raising arms can be shorter than normal, resulting in a more compact lift. As they needn't be monsters, the volume they will eat up inside the leg will be minimal.

Another major point for these things is they can be built out of scrap steel so the cost of each will be marginal.

The biggest drawback to them is that they look like they will be a royal pain in the butt to use, so I won’t want to move the bench too often.

The biggest issue, I think, is tying each pair of jacks together so both raise and lower using only one screw that turns both jacks. I can’t see how they can be raised independently without causing the bench to seriously twist, which would end up tearing the bench apart.

Like everything else I have done, figuring out how to build this thing will probably turn out to be its most enjoyable part of it.

By the way, while looking for some scissor jack ideas on the web this morning, I came upon this site – Jack-Bench.com.

Peace,

Mitchell