Welding casters to a "shop crane" base

I have a Harbor Freight shop crane
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber5915
The casters that it came with were quite lousy. I found some inexpensive Peerless 900 lbs rated 6" by 2" casters (the seller is 5 miles from me)
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item (0020380023
and I think that they would work better on this crane. I would like to just weld them to the legs of the crane. I hope that it would make the crane very mobile for moving loads around.
I have basically three questions
1. I am assuming that TIG welding casters to the far ends of the legs is not going to make this crane any weaker (possibly due to heat stress). The legs are probably made of ordinary mild steel and are unlikely to be carrying anything close to critical stress around the ends. The original casters were attached with 6mm or so metric bolts.
Is that a sensible assumption?
2. How far away from the weld area should I go to remove powder coating prior to welding.
3. After welding is done (TIG), what's a good simple way to paint it. I have some oil based tractor paint in a spray can, would be be a good application of it. I usually store this crane outdoors.
I would be unlikely to lift more than 1,000-1,500 lbs with this crane.
i

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Yes, you won't weaken the legs by welding to them - however, you'll trash the bearings in the casters due to the heat. BTDT, got the weld-spattered T-shirt. If the legs aren't wide enough for the caster base, weld a plate onto the legs, then bolt the casters to the plates.

On Wed, 30 Aug 2006 21:38:44 GMT, Tom Lawrence
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Um, I did not think about that. I am glad that I asked. What if I weld in little tacks? A little here, a little there, using a wet rag etc. That should work out OK, perhaps?
Anyhow, maybe it is better to make plates like you say, and to it this way, but in any case, thank you for the "food for thought". I am afraid that the size of the caster plates in relation to the legs is just wrong enough to make problems with bolts not being able to go through etc.
i

The only bearings you need to worry about are the swivel ones, they really aren't much of a bearing. Just two stamped plates with a ring depression and some loose ball bearings. If you wrapped the bearing area with a wet towel and welded the plates on with 1" welds using a stick or MIG welder you shouldn't heat them up enough to bother. The main rolling load bearings are held in by a bolt with a zerk on the head end. Just remove.
I'd caution you to not leave a heavy load suspended for any period of time (more than a few days or weeks) You will flat spot the plastic, the rig just won't roll any more. The plastic usually springs back ........ eventually.
Tom Lawrence wrote:
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Thanks Roy, I will post an update when I get them and weld them on. Good point on leaving weight suspended, which I do not want to do for safety reasons also.
i
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I should have mentioned that I would prefer to bolt them on......... But I have seen various applications welded on.
Ignoramus6539 wrote:
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On Thu, 31 Aug 2006 01:20:08 GMT, Ignoramus6539
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I've done several carts in the last year or so. Another option which has worked well for me is to make a caster mounting plate out of 1/4" plate, lay out, drill, and tap the mounting holes, then weld on the plates. Use cap screws to mount the casters. This lets you check fit first. Of course, as Gunner pointed out once, welding them on is quicker, at least as long as you don't need to replace them at some point.
Pete Keillor

Looks like the frame is square or rectangular tube. You might consider using rectangular U-bolts to bolt a plate that has the casters either welded or bolted to it (the plate) you can preserve the powder coat this way. Weld a spacer if required to the plate to facilitate caster bolt clearances etc.
Ignoramus6539 wrote:
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Consider welding the fixed casters directly to the crane and welding a plate diagonally to the other part. That way you can easily get 3 bolts into the swivel casters and the forth can be added by welding a nut to the crane from the inside. Nut on the inside weld on the surface. then grind flat. Drill a hole about the same size ans the nuts so they have plenty of weld area away from the threads. Clean the area around the holes and other welds about 1/4", then spray it with your tractor paint. I would remove the wheels from the frame before welding just to avoid cooking the plastic wheels and grease.
Glenn

I welded one caster last night. That was a fixed caster. I put a very wet rag next to the weld area to keep it a little cooler. The result was relatively nice.
I can now clearly see the point about possible damage to the bearing from heat. When I start welding on the casters that can turn, I will weld in small tacks maybe 3/4" long each, and will use that same wet rag very attentively.
These Faultless casters are extremely nice. If I spin a wheel, it keeps on spinning for a long time.
I used 150 amps when TIG welding, since I deal with relatively thick iron, the crane legs are made of 1/8" steel and the caster plates are about 3/16"-1/4" thick.
i

By now, I welded on two fixed casters and one swivel caster to the legs of my crane.
I tried pretty hard to keep a very wet rag very close to the weld area. For the swivel caster, also, I went in smaller tacks, like 3/4" long, and cooled the area liberally between tacks. I have one last caster left to weld on.
The swivel caster seems to be just as movable as before. I think that I will apply some lubricant there.
I figure that there is plenty of strength reserves in these welds and that they will be very low load welds. Since crane sits on top of casters, sideways forces tending to tear or shear the welds would only happen if a moving crane hits a crack or an obstacle.
i