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OK! I will be the first to admit that this is a total diversion from boat building but I LOVE building tools and machines!!! What actually happened is that I figureed out all the polished stainless tube work I would need for the boat. When you start listing it you see that there is a lot of it. The bow pulpit and transom rails are just the start. There are Dorade guards, hand rails, Bimini frames, stantions, radar antenna mount and sissy bars at the mast. After making up the list, measuring the dimensions and making up Autocad drawings I sent them off to the big three stainless tube shops in the boating business. Let's just say that when the bids came back I had a really good excuse for doing it myself.
I am pretty good with my little Miller 130 MIG welder and though I have been accused of being a Gorilla welder (strong but ugly), I am great with a flap wheel on the grinder and I can polish with the best. The thing I didn't have was a way to bend the tube. First of all, a pipe bender like the ones in the Harbor Freight catalog would not do. Especially for polished stainless steel. A little research showed that I would really need two different types of benders: A "one shot" ram type to do fixed radius bends like the ends of the pulpit and stern rails, Dorade guards and gate braces and a roller type to form the gradual sweeps.
A quick Google for tube benders showed that these things are outrageously expensive but one particular one shot unit on the Pro-Tools site looked pretty straight forward and reasonably priced. Then I found Earnie Leimkuhler's design for a roll bender in the rec.crafts.metalworking drop box. http://www.metalworking.com/DropBox/_2001_retired_files/ (Search for "Roller") Earnie's design is simple, straight forward and strong as an ox. I mentioned that I might build a copy on rec.crafts.metalworking and received an e-mail from Errol Groff who teaches shop in Connecticut. I believe he used Earnie's drawings for the top of his bender to teach CAD/CAM. Errol offered me the last one they made.
Now here is where the story gets complicated. Earnie's nice straight forward design just begged to be powered and I am not one to leave well enough alone. I also had accumulated a lot of hydraulic parts and pieces over the years and I saw an opportunity to use them here.
Here is the result. The frame is a left over pair of coffee table frames I welded up years ago and never finished. The motor came off my old DeVilbiss compressor (may it rest in pieces) the pump is a little 2.56 cu. in. Barnes rescued from another failed project and the solenoid valves and motor came from e-Bay.
I decided that If I were going to build a hydraulic power source it should be able to drive more than the roll bender so I added another solenoid and a couple of quick connects. This is the control end of the roll bender. The small box on top connects to the system with a coiled telephone coil and contains the up/down/left right buttons.
The long box on this side contains the circuitry 12VDC power supply and relays. One switch changes control of the solenoid valves from the roll bender to the auxiliary connections. I am waiting fro a 110V control transformer to finish the control box so the wiring is temporary and the pressure gauge (hanging loose in the lower center) will be mounted in the box at the blank space on the left. .
At the suggestion of a neighbor, I added a pair of optical limit switches either side of the drive roller. This will allow exact control of the bends by placing a piece of contrasting tape at the start and end points. The other switch changes the optical limit switches from dark off for sensing black tape markers on polished tube to light off to sense silver tape markers on regular steel tube.
This is a front view. The 1"-10 Acme drive wheel pressure screw is advanced with a 3/4" drive ratchet from a cheap Harbor freight socket set.
Pump and motor are at the bottom, Return filter and tank are center left. The solenoid valves are mounted on a dual D03 subplate at the center right.
There is a contactor behind the motor that is wired to the solenoid relays so that the motor only runs when either the rollers or auxiliary connectors require pressure.
Here is the drive roller assembly. It rides in a track milled from some left over 1.5" square CRS. The drive roller mount presented a problem. The shaft has to take some major side load so the bearing has to be pretty substantial. Fortunately, the drive roller slot on Errol's top plate was milled a bit oversize. I got a chunk of 2.75"x4"x6" CRS from Speedy metals and milled the top to fit the slot and the bottom to fit in the track. That gave me the full thickness for the sintered bronze bearings that the shaft rides in. The motor mounts in a welded up U shaped bracket made of 1"x4" hot rolled with a pair of Lovejoy drive couples tying the shafts together.
As I said, I used what was in my hydraulics collection and that was not the optimum combination. The motor is 2.56 Cu. in. displacement and the motor is 4.5 cu. in. That means I am wasting a lot of fluid through the relief valve to keep the motor speed down low enough to keep the tube from shooting across the shop and also limits the torque. The current motor only produces about 1,100 in..lbs. of torque and I figure I need at least 3 times that much to make best use of Earnie's very healthy design. I am going to trade for a 22 cu. in. motor so I can make full use of the pump's output and get about 3,500 in. lbs. of torque.
 Meanwhile the one shot ram is working great! The one shot bender is a modification of the Pro-Tools bender. Now that I have a hydraulic power source I changed from a 20 ton jack to a 4" cylinder. Pro-Tools supplied he die set and the roller. The frame is 1/4"x6" hot rolled with a piece of 2"x6" channel iron for the base.
 Most of the time was in building the lower die carrier. It has to carry the full load of the cylinder so I used a couple more pieces of the 1"x4" hot rolled and welded a bracket to the side that the platform bolts to. The platform is about .032" lower than the roller so that when the pressure builds the lower die will slide easily over the platform.
At a flow of about 2 GPM the ram will form a 4 1/2" radius 90º bend in about 15 seconds and control is excellent. Still, I have an extra limit switch so I may figure a way to add an adjustable mount for a bending stop so I can make repeat bends.
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