when I upgraded from a 743 bobcat to a 843B my backhoe attachment would not hook up. so the gear box that I was using to swing the boom had to go. the new plan is to go with a gear and rack setup.

Tom, are you going to cut your own rack and pinion to do this conversion?
I have seen a few versions of it, on different equipment.
Good luck with this project.
Dan.

Greeting tom, Did you get good torque with the old chain and sprocket system. Just curious..

Lu47Dan: it going to be a challenging project but with the room that I have to work with its the only way to go. It looks like there will be a ram remodel as well.

Tom, I figured that the tolerances would be pretty darn tight to try to use a existing rack and pinion gear.
If you could cut the rack gear then cut a radius into the back of the rack to match your cylinders outside radius. It might make it stronger with less distortion of the cylinder wall when you weld it on.
I will keep an eye on your progress.
Dan.

Dan: since I have to build the ram ends I was going to bolt the rack to the ram ends. the radius is in the plans.

matt: I had to go to 100 chain and the gear box was a little weak. there was no way to support the shaft which made the gear box split.

were do I find the flow rate for hydraulic hose.

maybe it was baum hydraulics that had a guide in the catalog..as I remember it deals with max fluid velocity thru the hose,not just flow..my thumb says 3/8 for up to 10gpm,1/2 up to 16gpm,3/4 up to 24gpm; anything bigger than that,you're on your own.Hose ID/port size can also be a limiter to how fast a cylinder will operate,depending on what you want

at this time I am thinking about reducing the hose size on my ram caps from 1/2" to 1/4". ruff estimate at this time is that the cylinder will be 3"x12" about .33 gal. scene it will be turning the boom speed isn't a concern. I have to build the end caps for this ram so the more compact the caps are the more travel I get on the cylinder and rack.

I think I have that in my spreadsheet calculator thingy. A link to it was in the recent post "Hydraulic motors". If you can run Excel files you should get some good use out this program.

I have not used the hose sizing part very much so....

moving on with test cutting the rack and gear. this is the gear cutter and the test rack that was cut at 1" on center tooth to tooth.

test gear is done I started out with a 1" spacing it was to small a tooth so I went to 1 1/2" that was to big, so I ended up with 1 1/4 spacing.

I think some shock absorbers are going to be needed. Maybe on the cylinder that drives the rack.

clint: this is the ram I will be using parts from and copying some parts.

Very cool Tom, nice work cutting the rack and gear.

that was just the test rack and gear to get the spacing right since I will be using the same cutter for both. the cutters are to expensive to order one that is suppose to cut rack and another one for the gear.

update: I got my steel for the gear from anchorage it's 7"X 3" 4140 hot roll so I had to anneal it before I could true it up. I was able to heat it with a brush burner and shop air in a make shift forage. after heating I put it in a bucket of garden lime to cool slow.

You will have one fine, tough piece of steel there! Looks like you still have your harder grain refinement on the O.D. and tough but ductile center. That should take a lot of abuse as it is, are you planning to heat treat it after machining? Great job on the test gears, I had people here that specialized in gears that wouldn't touch racks. Our old looms used several different sizes including a curved rack! Yes,there is a difference between a curved rack and a regular old spur gear. I learned that the hard way. Didn't hurt my feelings a bit to toss those 280lb curved nightmares into the scrap bin! Fine,fine work. Keep us up to date!
T

terry the bright spot on the outer side is were I was Turing it to fast and it was heat Harding. so I had to slow things down a little. after fitting and testing the parts I am planning to heat treat the parts. one of the problems is the rack is going to be cold roll which is going to be hard to heat treat.