Come-along / Push block

By Pat

Date 05-16-2010 00:40

Allan,

Thank you very much for posting the information on this sweet little gadget. Because it is hard to get an OK to purchase shop equipment that will not be used on a daily basis, we have not been able to get the powers that be to order a larger shop press. The offshore press we presently have is good only for 3/8" thickness and below.

Last night at work I made up something similar to what you have. At the top I mounted a lift truck load wheel, bearing, and axle that the rubber had came off of. I ground a slight "V" in the center to help track the chain. This worked great for straightening some square steel tube sections that were too long to place in the shop press. Only problem I have now is that our table top is only a piece of 4' x 8' sheet of 1/2" plate. The plate started to flex on the sides where the pullers were hooked. I am going to see if they will allow me to order a 4' piece of heavy beam to fasten under one end of the table. This should stiffen it up.

Can you or others suggest the type and size of beam to use for this. I would like to allow for a little over kill because we do have some high tonnage bottle jacks that may be used to apply pressure. I am also thinking about trying to find the same type of chain that normally comes in some of the hand ratchet pullers. This way I could have a somewhat smaller, but stronger chain................thanks again

By DaveBoyer (*****)

Date 05-16-2010 05:04

You might use grade 70 transport chain. It is not as strong as chain rated for overhead lifting, but it is better than grades 30 & 40, and redily available.

Perhaps You could use Allans other idea using the jack and chain to srtaighten the square tube, rigging the chain directly to the tube, not to the plate. This might require welding some temporary cleats to the square tube, if that is acceptable [might violate a code].

By aevald

Date 05-16-2010 06:04

Hello Pat, not sure of your current overall shop situation, but don't you possibly have some remnant sections of beam, channel, tube, or other structural shapes? If so, pretty much anything with some depth/thickness to it could provide that little bit of extra rigidity to help with limiting the flex. Even a mirror image of this set-up could be used underneath the table as you were employing the system on top to help with flexing. Hope this makes some sense. One additional note to go along with this sort of thing: as you are applying the force be very careful about where you position your body and also pay close attention to where others are relative to your set-up. The angles of the chain greatly reduce it's ability to stand-up to a lot of force and chains, cables, straps, and any other materials that are subjected to pressures will store energy that can release if it's stressed too greatly and can cause considerable damage to people and property. Glad to hear that this was of benefit to you, if you have "tricks" to share please include them on the forum here. Best regards, Allan

By Pat

Date 05-17-2010 19:29

Allan,

We have a somewhat meager steel supply. Most of it is sheet stock and thin walled tube for conveyor repairs. If we need anything over 1/4" thick we usually have to order it. I like your idea of the "mirror image". In the event they will not let me order some beam, that is the route I will go. I really could use some advice on what type and size of beam to request. I would like to get something that I will not have to worry about it flexing too much. I am also going to order it long enough so I have at least 6" extending beyond the table on both sides. I have a couple "D" rings at home that I will weld on the ends so I have a good sturdy attaching point for the hooks. These "D" rings are some of the largest ones I have ever seen. The ring is 1-1/4" in diameter so as long as I get a good penetrating weld, I should not have to worry about these things breaking loose. As I stated above, I sure could use some help in determining the type and size of beam. We had a steel catalog but it disappeared. I called our steel supplier a couple times requesting a new catalog, but still have not received one.................thanks

By Bob Garner (***)

Date 05-17-2010 21:44

I may be of some help in sizing the beam. Basically a stron-back beam has to yield (bend permanently) well after the peice being bent does so that the strong-back doesn't permanently deform. Stiffness of the strong-back beam (as opposed to strength) is not as important as long as your apparatus can adjust to the temporaty deflection during cambering. The strong-back beam should be wide enough that it doesn't roll over on you (torsional buckling). You should also attach the beam to your table so it can't buckle laterally.

In summary, the strong-back beam has to be stronger in bending than the piece being cambered - what is the largest size and span of plate or beam you will be cambering. Will you be applying a single point load in the middle to camber your piece? I can do a quick and dirty strong-back beam check for you.

If you have a pile driving job going on in town and they're driving H-piles, ask the pile driving forman for any cutoffs (if they are long enough). Steel H-piles are strong and wide and would be ideal for this application if they will fit. 'Course he'll probably want money for them. Sell him some welding.

Bob G.

By Pat

Date 06-01-2010 18:05

Hi Bob,

Sorry I did not get back sooner. If by cambering you mean bending back into shape (or close to it), I would have to say that 3"x3" or 3"x2" square and rectangular tube with a maximum wall of 1/4" would be the heaviest items we would need to bend. Quite often it will be lighter than this though. If you have ever worked with, or on conveyors, you probably have a good idea of the types of braces, support legs, and other parts, and the relatively low strength materials they use to cut costs.

I checked our on-hand supply of steel and discovered that we do not have anything near heavy enough to use as a strong back. I did however find a forklift mast in the dumpster that had been bent from tipping over. I am thinking that I may be able to use one side of that. It appears that it was cast and machined for the cam rollers for the fork carriage. But if that would not work, what size and type of beam would you advise to use..............thanks.