How to ensure concentric axles on a lawn roller?

BigBlue1 · Mar 23, 2020

I'm building my own lawn roller out of an ancient water softener tank. It is 12" diameter and about 45" long. I need to weld 1" solid rods on each end to attach the frame and bearings to. What would be a good way to keep them concentric? i.e. Parallel and inline so everything is straight?

Or would it be better to attach the bearings (I'm using flange bearings like in the picture below) to the tank and have the axles be on the frame? It may be easier to line things up and weld everything straight & plumb on the frame instead of making the axles straight/plumb/concentric on the tank. To do that I'd just have to make sure the bearings are flat to the plane of the tank ends.

Thanks,
Rob

Tractor Seabee · Mar 24, 2020

It would be easier to line up the axle to the bearings and the tank to each other it the axle went through the tank rather than stubs. I would put a doubler plate where the axle welds to the tank as they are thin and will crack under stress. Bearings on the frame naturally.

Ron

Grumpycat · Mar 24, 2020

Am thinking the ends of the tank may not take to the bending moment of an axle stub welded. But if you put the bearing blocks on the ends of the tanks then the stubs in your towing frame will be bearing the bending moments.

1" solid bar is stiff stuff, and expensive. Already have stock laying around? I'd suggest using a pipe through the tank but 3/4" has an OD of 1.050" which might be hard to find a bearing to fit.

If you are not going 60 MPH then being off center 1/16" shouldn't hardly be noticeable.

BigBlue1 · Mar 24, 2020

The tank is ancient, as I said. It is at least 1/8" thick and the ends may be thicker. I already have a design that includes added plates (3/8" x 3") and gussets to stiffen the axles. Running a rod as axle through the entire tank would make filling it with concrete a bigger challenge (the 2" opening is axial), plus I don't have a long enough piece. I have enough 1" solid rod to make axles (more than enough - about 50") but not 55"+ for a thru-axle.

I would anticipate 3-4 mph being the max, but I don't want to destroy bearings with a non-concentric set of axle stubs. The planned weight of the tank should be around 500# and another maybe 240-400# hung off the back of the frame using JD 42# suitcase weights. It will put a lot of stress on the bearings.

I'm fine putting the bearings on the tank and stubs on the frame if that makes alignment easier. My design can accommodate either option.

I think I have the strength of the materials covered. 2x2 1/4" angle iron for most of the frame. 3/8" x 3" bar for the suitcase weight brackets, same for axle supports (with gussets). I'm just trying to figure out the best way to keep the axles straight.

Rob

ruffdog · Mar 24, 2020

Stick the rod through the tank measuring the best you can with a tape measure. You are not even going to notice it if it is off 1/4 inch. I have used them much worse than that and the frame just oscillates back and forth...no problem.

BigBlue1 · Mar 24, 2020

I actually figured out a solution last night that I think will work well. It would be tough to describe in words and I don't have pictures yet, but part of it involves running a pipe through the tank to get the flange bearings mounted correctly at each end. Then I'll remove the pipe before filling the tank with concrete. For the frame I'll use a single length of axle rod and weld both sides of the frame rail to it, then cut the rod to separate. That will allow me to square things up together. Those two things should keep everything pretty darn close to concentric and axial. I'll post pictures eventually.

Sometimes I do my best design work in my head while I'm trying to fall asleep...

Rob

dragoneggs · Mar 25, 2020

Rob, that makes sense to me. I was thinking the tank was to be filled with water. Do post pictures as I am curious if I really understand your design.

coxhaus · Mar 25, 2020

It seems like to me 1 inch rod welded to 1/8 inch plate might not hold spinning it. I think the 1/8 plate is going to flex and break away from the tank. What if you could insert some of the rod in the tank to allow the concrete to bond to the rod to help hold it in place. Maybe weld some rebar on to the rod inside the tank to allow the concrete to hold it.

My other thought is what about using pipe in pipe. Put a piece of pipe the length of the tank set in concrete. Then add a longer pipe through the other pipe. Grease the inside pipe real well. Don't use bearings use pieces of pipe the same diameter as the pipe in the tank. Weld your frame to the outside large pipe. You can thread the ends of the smaller pipe and use pipe caps to hold the small pipe in place.

KennyG · Mar 25, 2020

coxhaus said:
My other thought is what about using pipe in pipe. Put a piece of pipe the length of the tank set in concrete. Then add a longer pipe through the other pipe. Grease the inside pipe real well. Don't use bearings use pieces of pipe the same diameter as the pipe in the tank. Weld your frame to the outside large pipe. You can thread the ends of the smaller pipe and use pipe caps to hold the small pipe in place.

I will respectively suggest that this is not a good idea. I started out with this approach when I built my lawn roller. It didn't pull smoothly and the first time I tried to move it when it had sat idle for a few weeks, it bent the frame. I added pillow block bearings and all is good. Mine actually has two ways to rotate. I ran a large pipe completely through the tank and welded it in place. Then I ran a second pipe inside that one that rides on the bearings. I have clamps on the smaller pipe to keep the tank from moving from side to side.

I fill mine with water but if I wanted to fill with concrete, I would still run a pipe completely through. To fill with concrete, I would just cut a hole in tank and fill with concrete to leave a smooth surface.

BigBlue1 · Mar 25, 2020

The rods/axles will be mounted to the 2x2 1/4" angle iron frame through a hole (protruded on back side), welded around on both sides. It will also have gussets on the bearing side. The flange bearings will be mounted onto 3/8" x 3" flat plate which will be welded to the tank at each end. I suspect that it will be pretty stout. I could be wrong.

The pipe in pipe idea is a good one, but I already have all the parts and materials for my design.

Rob