Brian's Chopper and steel tubing

[diecycle]

I saw how both Jeff and Brian posted about steel tubing being used for hydraulics being a big No Go.

From the context it seemed the problem was steel tubing eventually leaking or bursting.

My question is what if thick steel tubing was used. What if the frame tubes (could even go all the way to .250 thick) were also used as hydraulic tubes.

I was thinking high pressure "regular" hydraulic hose comeing off the motor (so there is some flex) connecting to the swingarm or frame tube that now doubles as a structure tube and a hydraulic hose, the hydraulic fluid follows along the swingarm or frame tube for a bit and then back to regular hydraulic hose (again to take up vibration/flex) to connect to the pump or reservior or whatever.

So instead of running the high pressure hydraulic hose through the swingarm or frame the frame or swingarm IS the high pressure hydraulic hose.

Is this asking for problems? What are the opinons on how thick the steel tube would need to be to not have to worry about cracking, breaking open leaks?

[x4158]

That would yield an interesting look, especially on a swing arm like LeRoy's...



Perhaps a thought for his next build...

MH

[Brian]

Actually, I don't recall Jeff or I ever saying steel tubing was a no, no. DiezelSmoke was the one who mentioned having problems with tubing. It's like anything else..... NOTHING is 100% perfect. Nothing! (except death and taxes) In the world of mechanical machines, have you ever found a component that NEVER fails? I haven't. Steel hydraulic tubing is no different. Sure it can fail but the type of machine it's used on, how it's mounted, vibration, weather conditions, road salt, etc, etc all play a part in how long in how long it will last before it fails. I don't remember if DiezelSmoke mentioned what type of machines he's seen the failures on but I'd be willing to bet there is a reason why they are experiencing problems regularly. Most heavy construction machinery uses steel tubing and you almost always see a hose fail long before the tubing. Example: Look at the arm on almost any big excavator, usually you'll see steel tubing running the length of the arm with short pieces of hose on each end to make the connection. Usually when I see a broken hydraulic tube on a piece a machinery it's because something hit the tubing or rubbed against it long enough, physically damaging it, which caused the leak.

I certainly wouldn't consider steel tubing a weak link.


That wold be cool to see the swing arm tubing used as the hydraulic plumbing. One thing to keep in mind is.... the larger the diameter, the heavier the wall thickness needs to be to withstand any giving pressure. It's like a hydraulic cylinder.... if the oil has a larger surface area to push against, the greater the force will be.... same with tubing.

Brian.

[diecycle]

Thanks Brian, it wa LeRoys build that got me thinking about it. At first I was thinking about running the hose through the steel tubes back to motor, but then I thought the steel tubes could be the hydraulic hose.

You were right in your analogy of construction equipment. I went looking at some front end loaders and such and saw the hard line to rubber hydraulic connections, so it seemed that the steel tubes could be used in conjunction with rubber to handle vibrations and bouncing about. I thought if it held on heavy construction hydraulics it would hold on a street bike.

[detroti]

to do the formula its hoop stress p X r / t

[DiezelSmoke]

The steel tubing failures I was describing are on the bend areas. They are on construction and garbage truck equipement. They experience frequent shock loads and hit relief pressures often throughout service. I actually like steel piping except when it is bent and used in service as I described. The use on a bike is probably a more forgiving atmoshere.