DOM and Frame Performance

The steel terminology changes from country to country, when you say you use standard steel tubing, are you using seamed tube or dom (drawn over mandrel,seamless).

I live in Australia and without checking the legislation am sure the frame would have to be dom, to be accepted by department of transport. How would this effect the frame performance. Also dose the removal of the down tube (center) have any effect on the torsion or twisting strength thus altering the handling of the bike (ie walla) when used with a big twin with separate transmission. Regards, Brenton Dunne.

Here's Your Answer:

The analysis was ran with DOM tubing - Drawn over mandrel - seamless steel tubing. I checked the Australia website and was not able to find any documentation on frame construction for motorcycles. There was a lot of documentation with regards to emissions, sound, lighting and other items but I did not find anything that specified the type of tube. Just to be safe, I recommend going with seamless, DOM steel tubing.

I ran FEA using seamless tubing and the frame held 1000 kg. The tubes did not deform to failure with this load. The failure was at the rear axle plate. The frame easily held a load of 1000 kg with only 0.05" of deformation. The loads were well below yield strength of the steel on the tube. (See images below)

Then I removed the center down tube that connects the backbone to the horizontal pieces on the two down rails. I ran analysis with the same
load case of 1000kg. The deformation on the frame with this load is 0.09". The tubes did not yield under this stress and change of geometry. You can remove this tube or even turn it so that the tube is arched upward for added strength if you like. Please see dom tubing and bobber frame images below showing exaggerated deformation and stress.

The frame as designed is very rigid and over designed for the loads
that it will see. There should not be any issue with torsion or twisting since those load cases will be much less than the 1000 kg load case that was tested. If you have any additional concerns,
please feel free to let us know and we'd be happy to take another look
at it for you.

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May 17, 2010
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Tube Suppliers in Australia
by: Eazy

Ok want to do the Pro job heres the site for your tube suppliers.
http://www.racetechsteel.com.au
There ya go. what they havnt got dosn't matter they supply for aircraft watercraft and drag applications and anything less. they have a full inventory of stock in the online catalog.
The rest is this site and the chopperbuilders.com and Knuckleduster.com if you are serious you need to use all these sites to aid you in you project and the getting through red tape and bullswarze you will find if you look for it within, Get the drift. Good luck, dont for get to pick the brains out of all suppliers you meet.

May 17, 2010
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Tube Material
by: Eazy

Dom is great from what I understand and from what I personally know as far as pipe what I'm using its galvanized has a MPA strength of 250 DOM is 450 and ERW is 350 so ive gone heavier than speck the stronger tube allows you to go lighter. I'm using 3.4mm wall wick is over kill in another direction. So effectively what i dropped i picked up but gained weight, I don't think it matters on a Harley unless your PRO dragging, Please don't give me the government rego crap (get the hint).
My frame is much stronger than any stock Ive seen If I'm willing to put my ass on it, I know this because the welding process I used The Henrob DCH 2000 Gas welder so heat stayed local and min or no distortion. So I kept strength there as well.
with dome you will need to have your chassis heat treated after tacking and welding.

I welded mine straight on my jig and used a process of moving from one weld to another before any weld was entirely compete another rule of thumb broken if i was using another welding process such as Mig or Tig then I tune my frame over and go again. some welds even out of the jig.
If you go to the sit mentioned above you will learn heaps, Like did you know you can use a stick welder for chassis work, it comes down to Rod selection and process.

Dom will give you shit all the way as i understand it, Wanting to twist and warp as it has memory. Chrome molly is another optune 650 MPA strenght. In Australia there is a place in Melbourne if you want to go the High spec route they supply all the DOM, EWR and Chome Molly bendenium you want. There's a drag application specialist mob. Sorry I cant think of their name but I got a mention on my Website http:www.aussieshovelhead.com so I've got all the info there. Warning the site has been spammed on some threads but not the one you want. Get into forums go to the choppers thread then go to contacts or supplies you should find it.

Save dollars and do full plan. After my experience although it was interesting I would go to Attitude Choppers Australia they build wicked second to none style hard core straight out they really live up to there name and sell full chassis for $2500 up (check em out) I am not affiliated Just my take on it.

People used to frown up on such after market frames because they were not original Harley Hmmm, now look at the scene its turned on its head. Good luck email me bucketwarrior@yahoo.com.au I'll help otherwise.

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