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I am just starting a project to build a mobile base for my J-head Bridgeport and though I would start a build thread. Best I can figure the BP ways in just north of 2200 lbs is quite difficult to move around even on roller rods. The BP had been sitting in the middle of the shop getting converted to CNC but now needs to be moved to a new location. Not only will the mobile base allow me to move the mill around it will raised the base up about 3-1/2" to accommodate the new longer ball screw I recently added on the knee drive.
Initially I was going to put a wheel on each side of the base at the center of balance but I found the balance range was only about an 2 inches so I changed the design to use three wheels. It will have a castering wheel in the center rear and two non-castering wheels up towards the front of the base on either side. All the wheels will extend and retract by hydraulics using a base mounted hand pump. When off the wheels it will sit down on 4 adjustable 2.5" dia. leveling pads. This should be a fun project and a good learning experience. To make it even more of a challenge I will be making my own hydraulic cylinders and hand pump. Though I haven’t finished up the base’s CAD drawings I have started milling out the hand pump.
The pump body starts out as a 3.5 x 3.5 x1 inch block of CR steel. Been very interesting drilling deep passage holes. Had one #24 drill that was about 3” deep. The chuck loosened up part way through and the bit got stuck. Vise grips to the rescue –no harm done. Then, trying to drill the ½” hole 2.5” deep for the pump piston cavity I broke off the a ¼” pilot hole bit down 1.75” . Had to use an end mill to cut the drill out then over cut the hole for a brass sleeve, better that way anyhow. So far all the drilling has been by CNC. Problem is you get no feel like a drill press.
The hand pump is progressing. I have all the passages drilled, fulcrum machined and the brass piston sleve ready to go. I still need to turn the piston pump rod, and make the two valve poppets. Only had a few minor machining glitches since the broken drill in the pump cavity. I did end up drilling one of the passage holes in the wrong spot. I re-drilled the hole and will just plug off the wrong one.
I had accidently measured the wrong spots on the master cad mode.
Craig
I finished up the hand pump today. The initial tests did not go well, I couldn't suck up any jack oil into the pump. This turned out to be a combination of things. The oil was way too thick, the poppet spring force was too strong and the intake flow path was too small a diameter. I switched from jack oil to hydraulic fluid, used a longer lighter spring, increased the input tubing diameter and profiled the poppet to provide more clearance to the cavity wall for better flow around the poppet. It pumps very well now and will easly make 2500 psi though only 800 psi will be needed for the base.
YouTube video of the pump in action:
Now on to the wheel acturator cylinders.
Congratulations on your success so far... looks like it's going to be a nice design. Thanks a lot for sharing!
After taking some time off in December I am back working on the mobile base. Today I cut the first wheel mounting plate, three more to go. These plates will hold the forward left and right 5" diameter wheels that get hydraulically rotated down into position when the mill is raised off the leveling pads. The material is 1/4" plate which may be overkill but I needed some thickness for the 1/2" dia flat head cap screw used for the wheel axle. The plate on the other side of the wheel is threaded for the axle bolt. The wheel came with a 3/4" hardened sleeve that accepts the 1/2" axle bolt.
The countersunk hole is almost 1" in diameter on the surface of the plate and I didn't want to spend $50+ for a 1" dia MA Ford for just two holes. So I fabricated my own from some 1" water hardening drill rod. Cut a point at 82 deg on the lathe then cut a flute on the mill followed by hardening with a propane torch. It was a little too much to cut that big countersink hole and the mill bogged down. So I ended up step wise milling an 82 deg slope on the hole with an end mill, then just cleaning it up with my shop built countersink. Worked great at 120 rpm and .1 IPM feed.
Craig
Today I finished up the wheel assemblies. TIG welded on the top covers and cleaned off the mill scale so they are ready for painting. Now its on to the hydraulic cylinders.
Craig
I haven't posted an update in a while but I have been making progress. The side wheel assemblies are almost complete. The only thing remaining is to weld the cylinders to the bases.
I spent the last week or so learning how to thread mill. The push rod end of the cylinders have internal threads (1-1/4" -12 ) to accept and end cap/bearing for the push rods. I while back I watched one of Hoss's YouTube videos on thread milling and fugued I would give it a try. Thanks Hoss. I used a DIY milling tool fabricated from a 9/16-12 hand tap. All the teeth except three on one flute were ground off. The tool worked very well and cut nice looking threads but I am sure a real thread milling cutter would work better but this one was free. Only had one D'oh! moment -- the first threading cuts were all conventional milling but on the last part I though I would try climb milling to see how that worked out. So I changed the program from a G2 to a G3 and I got a really nice looking LEFT handed thread. D'oh! D'oh! D'oh!. I just gots to learn to think things through before pushing cycle start.
The first photo is all the parts then assembled with cylinder retracted and extended.
Next its on to the real wheel and its cylinder and finally the frame.
Craig
Been making progress on the mobile base. The side wheel assemblies are ready to mount after painting and I have started cutting parts for the center rear castering wheel. I should have all the parts for the hydraulics finished up in a couple of days then I can start cutting bar stock for the base frame.
Craig
Today I did a little TIG welding and sealed off the end of the hydraulic cylinder for the rear wheel assembly. Also welded a flange to the other end. I need to do a lot more practice on the TIG! The welds will hold but they don't look like a stack if dimes by a long shot.
All the pieces for the rear wheel assembly are completed an it has been assembled. Didn't get a chance to test it at hydraulic pressures yet but it works nice on shop air. The total stroke is 2.25" like the side wheels.
Now its on to welding up the base frame.
Craig
Over the past few weeks I have been working on the main base weldment. I finished up the the final grinding this morning then loaded her in the pickup for a trip to BR&F Spray to get media blasted and powder coated.
This is no wimpy sheet metal base, rails and cross members are 3" x 3/8" HR, top plates are 1/4" HR plate, weighs in at 120 lib without the wheels and hydraulics. It was mostly stick welded (NOTE: got to get a MIG) except for closing the bottom of the hydraulic reservoir where I used the TIG torch.
Welds may not be x-ray quality but they will hold my BP just fine.
My mill is white but decided to make the base black, think it will be easier to match the black with rattle can paint if things get dinged up.
Craig
wow !! thats some excellent work and well thought out . im impressed
Wow. Nice!!!
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