Sunday, December 9, 2012

Not Quite A Rube Goldberg Device

It doesn't have enough moving parts of course. I was trying to find a way to make it easy for my wife, who has some shoulder problems, to install the snowplow on the front of our TrailBlazer. The obvious solution was two pulleys mounted to the ceiling, but of course the problem then is still the weight of the plow at the end of the rope. So I started looking for counterweights to roughly balance the weight of the snow plow blade.

 My first try was a plastic bucket filled with rocks. Fortunately rocks are not in short supply on my property. However, the plastic bucket full of rocks was not quite heavy enough to be an effective counterweight; it only weighed about 30 pounds I think, which still left quite a bit of weight that had to be controlled while attempting to slide the snow plow over the frame. What do I have lying around that would be easy to use as a counterweight, and is very heavy?










 




As you can see from the attached photographs, the obvious counterweight is a military ammo can that was of course already filled with ammunition. Rest assured, this was almost as heavy as the snow plow blade. I put a few more boxes of ammunition in the ammo can, and it is now close enough that I only had put a few rocks on top to hold the snow plow blade up in the air.

 So what happens when she unhooks from the blade?  Won't that ammo can hurtle towards the floor?  Yup.  Tomorrow I will find a 60 pound piece of steel scrap at Pacific Steel, drill a couple of holes in it big enough for the hooks that go on the snow plow blade, and then when she is done installing the blade on the frame, she will move the hook the steel scrap, which will prevent the ammo can from crashing down.




10 comments:

djmooretx said...

I have to say, the "move the hook to the steel scrap" step fills me with foreboding, particularly since the person performing the step has reduced strength and control to begin with.

If I understand the setup correctly, it sounds like she's going to be hanging on to 30 pounds of ammo can while she transfers the hook.

There should either be a brake on the line, or something under the ammo can, so that the line is slack while transferring the hook.

Excuse me if I've missed something obvious, but I thought it worth pointing out since it's a safety issue.

Fred said...

Hmm....I'm assuming you've already investigated the idea of an inexpensive chain hoist or cable come-along. Why didn't those work?

Clayton said...

Good point, and perhaps it makes more sense to have the ammo can land on a solid surface in the up position.

Unknown said...

Since you're using block and tackle anyway, why use a counterweight? Just double or triple the blocks to get sufficient mechanical advantage.

David said...

or - replace your counterweight with a come-a-long that connects from the blade to the ropes coming down from your pullys.

Keep your dual rope/pulley points on the blade and ceiling to reduce the thing swinging. Add a cross bar between your plow mounting points to attach the come-a-long to.

If a straight pully arrangement like you have set-up still is too much for her shoulder to crank the come-a-long, then replace your pullys with block and tackle.

Best of all - nothing falls, uncontrolably. If you stop cranking up or down, it just stops and hangs there waiting for what you want to do next.

Clayton said...

I think the simplest solution is to find some big ugly piece of furniture that is about 5-6 feet tall, put casters under it, and when the blade is on the frame, push the furniture under the ammo can so that it is an inch or two below the top of the furniture, push up (which is easy because the blade is still counterbalancing the ammo) until the furniture slides under the ammo can. Unhook the blade.

When it comes times to reattach, the rope with the hooks doesn't have any load on it. Attach, push up the ammo can, roll away the furniture, and everything is counterbalanced again!

Jim Dunmyer said...

Harbor Freight has several electric hoists, starting at $99.00. That one is listed "store only", but they show one for $149.99 that's rated at 1100#. Or, you can get a deer hoist from Cabela's for 20 bucks that's essentially a block & tackle, rated for 500#.

That rig you show scares me.

donumvitae said...

How much can your wife comfortably pull?

If the blade weighs 60 pounds, can she handle a pull of just over 15?

Try starting a single length of line at a fixed anchor on the roof, down through a block attached to the blade, back up to a fixed block on the roof, back down through a block on the other handle of the blade, back around one final fixed block on the roof, then lead it to a cleat of some sort.

This should result in the blade going up and down in a pretty controlled fashion (if it tips a little, just cleat the line and it would be easy to straighten out).

If you have a wall available, you might try something like this, as it would make it quick and simple to secure and release the line.

If this is still too much weight, you can bring the pull down to about 8-10 pounds by using a double/fiddle block on each blade handle, with a correspondingly longer length of line and more blocks on the roof.

The counterweight does look like an accident waiting to happen.

Wayne

Windy Wilson said...

I'm with the Unknown commenter above; a more complicated block and tackle arrangement would increase the length of the ropes pulled to install and uninstall the blade, but it would reduce the weight of any counterweight and reduce the strength needed to pull on the ropes. And some kind of brake or camlock might be necessary.

PhaseMargin said...

Since your wife has limited strength, might not a cheap electric winch serve well here? A cheap 1-ton winch will run you $60 at Amazon, for example. That would eliminate most of the risk of things falling and there won't be problems of grip strength or shoulder fatigue.