Low Profile Overhead Shop Bridge Crane

[ETC57]

Walter,

Is your ceiling finished?

I too am working with a low ceiling but it is open trusses, so I will move all the lights and the door opener up between the trusses and put 3 rails up between the trusses as well leaving only the cross rail hanging below the trusses. this should keep my trolley within 4 to 5 inches from the bottom of the truss, while giving me complete shop coverage.

Jerry.

[starlight_tools]

Jerry

Ceiling is drywalled, but was never taped and filled.

My plan is to cut out two strips of drywall where the rails need to be mounted, then fill in the holes afterwards.

If absolutely necessary, I will add a few cross braces, ie steel I beam, or tube to give extra support for the joists, but would prefer not too.

Overall, I do not have trusses going in the right direction.

Walter

[f350ca]

Walter
Found the formula for lag bolt allowable withdrawal load. "Marks Standard Handbook for Mechanical Engineers" Won't say how long ago I bought that book for school. Can't be that long ago its only the 8th edition.
Sorry don't remember how to write formula on the computer but here it is.

P=1800D(to the power of 3/4) G ( to the power of 3/2)

Where D = shank dia of lag
G = specific gravity of wood

Most construction material is SPF spruce pine or fir.
The lowest being pine at .43
So for a 3/8 lag in pine side grain you get 243 Pounds pull out strength per inch of thread.
Think I went 2 1/2 lags to get 2 in of thread into the joists or 486 pounds per lag at 2 per joist 972 pounds on each joist. Spread the load over 3 joist gives 2916. Derate by a factor of safety of 3 and you get close to 1000 pounds if the load is at the wall, worst case scenario.
My ceiling was sheeted with chip board which I wasn't about to remove.
Not sure the 1/2 inch bolts your thinking of using would give much more strength with 2 inches of wood for pullout on the joists. Don't know where you'd get the numbers for that.
Just food for thought.

[starlight_tools]

OK so the numbers have been crunched.

With the 3 x 4 x 0.250 HSS tubing, the maximum SWL is 2300 lbs. The limiting factor is the 1/4" flange thickness of the beams.

By using 3 x 5 x 0.375 HSS tubing, the maximum SWL is 3600 lbs. The limiting factor being the joists which the system will be supported from. This is also based on the bridge trolley being lengthened to 43 inches long and having 11 wheels per track so that the weight is distributed by at least 3 joists at any time.

So now to finish redrawing the prints, then to start amalgamating the materials.

I would like to thank everybody for their input, especially AAB who I met through the PM forum.

Walter

[Mayhem]

Sounds good Walter. I am looking forward to your build, as I am planning on doing similar, or possibly a mobile gantry.

[starlight_tools]

(08-01-2012, 09:37 AM)Mayhem Wrote: Sounds good Walter. I am looking forward to your build, as I am planning on doing similar, or possibly a mobile gantry.

Mayhem

AAB is actually a bloke located in Melbourne, Australia. He has been very helpful with reviewing my numbers and making sure I do not pull the house down on top of myself.

I have all the steel (6" x 20' I beam and HSS Tubing), Casters and even the hydraulic jacks to build one of the telescoping Gantry cranes, but I have a big problem with it. My driveway/parking lot (WHU) is sloped about 3 feet over about 75 Feet. Just enough that the gravity of the situation takes over any time I try to lift anything. I currently do have a 2 T engine hoist and whenever I use it, I have to run a winch from the back of the shop out to the hoist so that I can keep it from scooting down the driveway and taking out any vehicles that happen to be passing by at the time.

The gantry may get built in time, but probably not before I either redo the driveway or go back to my original plan and pour a Concrete retaining wall down both sides of the driveway and embed a gantry track in it.

If you have a flat surface to work from, and lots of room in your shop, the gantry is a better choice as it can be taken where you need it.

Myself, not flat, very cluttered and low headroom, leaves the bridge crane as the best alternative, although definitely overkill for the space, will be very handy when completed.

Walter

[DaveH]

(08-01-2012, 03:24 PM)starlight_tools Wrote: Mayhem

AAB is actually a bloke located in Melbourne, Australia. He has been very helpful with reviewing my numbers and making sure I do not pull the house down on top of myself.

Walter

Now that is important

DaveH

[Rickabilly]

Hello Walter,
I have made similar tracks previously using very similar track dollies, and in the first instance I decided to mill the slots, mine were a full inch wide, in 1/4" wall thickness 4" x 4" tube and the slots were not all the way to the ends of six foot long tracks, Long story short 5+ feet of 1" X 1/4" milling takes time and for my money is just tedious, I was making ten of these beams for a customer, luckily I was also the design engineer on the job, A quick amendment to the drawing and I was free to use a Plasma cutter to do the slot, and by judicious use of a powered straight line cutting jig the last nine beams were cut in the same time as the first one was milled.

My point; if it isn't critical for dimension or finish it is often preferrable to go with a good clean plasma cut rather than spending weeks and a load of cutting tools trying to mill structural steel parts.

I hope this is of some value.
Best regards
Rick

[starlight_tools]

(08-14-2012, 02:40 PM)Rickabilly Wrote: Hello Walter,
I have made similar tracks previously using very similar track dollies, and in the first instance I decided to mill the slots, mine were a full inch wide, in 1/4" wall thickness 4" x 4" tube and the slots were not all the way to the ends of six foot long tracks, Long story short 5+ feet of 1" X 1/4" milling takes time and for my money is just tedious, I was making ten of these beams for a customer, luckily I was also the design engineer on the job, A quick amendment to the drawing and I was free to use a Plasma cutter to do the slot, and by judicious use of a powered straight line cutting jig the last nine beams were cut in the same time as the first one was milled.

My point; if it isn't critical for dimension or finish it is often preferrable to go with a good clean plasma cut rather than spending weeks and a load of cutting tools trying to mill structural steel parts.

I hope this is of some value.
Best regards
Rick

Rick

Amazing how there are no new thoughts, just ones that have been modified a bit. also there are many ways to skin a cat. LOL

I have a few options to choose in cutting these slots. First is the track burner, I have both Oxy and Plasma torches for my track burner, but my track is only 6 feet long, and the beams to be cut are 24 feet long. I had the steel supplier quote out having the HSS tubes precut before they supply it, but they wanted way too much and even at that they spec'ed +/- 1/8" from centre of tube and I want to be closer than that in tolerance.

Second option is to cut them with a metal cutting circular saw. I have the Milwaukee 6370-21 Metal cutting saw along with some extra blades, but need to see how it will work cutting 3/8" thick material. Should be able to jig it so the saw runs parallel down the length of the tubing and if cut from each side should be nicely centred.

Milling is my last option and although it would give a nice clean cut, I would have to re-arrange the mill in the shop to handle the length. this is a task that a horizontal mill would be ideal for. Oh well, mine is a vertical mill and I do not have the horizontal adapter so onto other ways of skinning this cat!

The Chainfall arrived a few days ago. 2 Ton, and seems to have a small size that will work well in the space required.

Walter

[Rickabilly]

Hello again Walter,
When I said judicious use of the straight line cutter, what I really meant was that I made a "roller carriage" out of skateboard wheel bearings, that located directly onto the square tubing and held a Urethane drive wheel fitted to the straight line cutter's drive pinion which gave the unit an unlimited cut length and most importantly gave good accuracy to the lateral location of each cut, something like this might be an idea for your job.

The carriage that I made was really quite basic, the main section was really just an 8mm 5/16" plate with some 8mm bolts tack welded to it to make the axles for the bearing/guide wheels of which there were four riding against the "Cut" face, two on each side of the faces adjacent to the cut face and a last single wheel on the back to keep every thing tight , I used an old rubber trolley wheel for this one as the give in the rubber was enough to provide tension without any elaborate spring systems, the torch was held by a really rough home made clamp which was attached to the carriage by a c bracket with threaded rod perpendicular to the axis of the cut face, the torch bracket itself was attached to four nuts welded together to make a really long nut so turning the threaded rod could adjust the location of the cut across the tube, my plan was to cut all of the right sides then adjust the torch position with the threaded rod gizmo then do the left sides, as it happened, I just turned the carriage around and went back the other way, without any adjustment at all.

Two points to consider;
1, the square tube will spring when cut, mine wasn't cut through the ends so was somewhat protected in this case, but having done this sort of cutting on other jobs with cutting discs, milling machines, (H & V), Oxy acetylene and Plasma, they all spring either open or closed, and it's simply due to the manufacturing stresses, I did a smaller guide rail out of 1 1/2" x 1 1/2" x 0.060" wall, that was twenty or so feet long, we cut this one using a cutting disc on a grinder, using a fence to retain accuracy, as soon as the last 1/4" of the first side was cut, the length "cork screwed" itself, this piece was also curved in a section roller to conform to a long curved concrete wall, and the piece was usable but we had to twist it into shape while bolting it in, the straight pieces usually spring open or close up on the cutting wheel as the last bit is cut through.
and finally;
2, if using plasma or Oxy, the spatter/swarf sticks to the back wall really hard sometimes, I used a strip of hardboard which eventually caught fire, but it was cheap enough, and saved a load of work, ideally a piece of thin sheet metal folded into a channel and sitting inside the square will work wonders. I suppose a piece of tough string and a couple of pulleys could automate the movement of the channel, but this is probably over kill with a capital OOO.

I hope this helps, best regards
Rick