Roll Hoop Bending

[Chris Bova]

We are a first year team and tried to save some money by bending our own hoops the problem is we designed for a 6" radius for the top and the die we have for the bender is only about 3" so we had to do tons of small bends to get the correct radius and angles. The hoops dimensions are VERY close to the design considering the method we used to bend it. The problem lies in the definition in the rules, something to the effect of no evidence of wall failure, or something like that. There are imperpefections on our hoop just because of the method used.

How do the judges inspect this sort of thing? I would assume it would be a thouroough check because of the safety aspect on the hoops. What constitiuts "wall failure" the tubing is not kinked it just has bumps where the die ends. (1"X.095 4130). We thought about adding some sheet metal on both sides of the top to act as a "filter mount" about the drivers head but werent sure if it was pemissible by rule to hide the bents...

"3.3.4.1
(D) The minimum radius of any bend, measured at the tube centerline, must not be less than three times the tube diameter. The bends shall be smooth and continuous with no evidence of crimping or wall failure."

That tells me we are no good

For those who have it bent, what is the radius of the top bend? Are they mandrel bent? What type of shop? (welding, race...)

For those who bend themselves, same question.

I talked to a custom welidng and fabrication shop who helped us in the past and he did not have mandrel equipment but he had a 10" radius die but he said it would stretch the tubing too much at the top for the angle we needed.

I have some digicam pics of the hoops but im not sure how to post them.

Sorry for the long post

Chris
UNH FSAE

[Daves]

So it reads like a 3" bend with 1" pipe is ok.

http://www.letu.edu/formula

Formula Photos & Links (http://what3542.5u.com/dave/fsae/formula_photos.html)

[Farls]

The guys who bent our hoops pack them with sand, plug the ends, heat the tube and then bend them. If you email me the pics (c dot farley @ ugrad dot unimelb dot edu dot au), I can post them for you.

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Views expressed do not necessarily reflect those of my team or University.

[Charlie]

I remember my first car in 2000 had a pretty crinkly bend in the top of the main roll hoop. We didn't get any flak about it. I wouldn't recommend it, but I know tubing can be expensive and if you are only working on your main roll hoop now, you've got a long road ahead.

Maybe a better idea would be to design around the tools you have. In other words, if you have only a 3" radius die, make that a constraint on your roll hoop, if that is possible. Make the best of what you have.

-Charlie Ping

I just need enough to tide me over until I need more.

[Beast]

I know the judges took a caliper and measured the OD looking for the narrowest part. Our hoop had ovalize slightly and they almost made us add material to the entire bend, basically a huge gusset.

From your description, I'd be worried about the bend, maybe send the pictures to the person in charge of further explaining the rules and see what they say.

http://www.sae.org/students/formulaseries.htm

[JonBoy]

http://www.ercolina-usa.com/megabender.htm

The local dealer of this mob let me play with one of his benders to do our roll hoops, see if you can find a similar machinery distributor. I think I made 2 x 112mm bends (or so...) (flat top) for the main roll hoop, same for front.

cheers

j

[Chris Bova]

Thanks a bunch guys. I finally found a local race shop (www.ricracing.com (http://www.ricracing.com)) who has a "Hossfeld" bender he offered to let us use. He owner was actually very good friends with Carroll Smith so he is aware of FSAE. Hopefully this will work well with the hoops. We are taking our material down there Tuesday AM to try again with the hoops. I think this shop will be a very valuable resource for us. I will keep you all posted on the results.

Thanks again,
Chris
UNH FSAE