So, this may be a stupid idea, but I am considering building a rpu frame from 2"x3" Ibeam. The bean will be cheap or free! It is pretty heavy, not sure of the exact thickness. My thought is that a drilled I beam frame could look pretty cool. To add rigidity I was thinking of running round tube cross members from the holes on one side to the other, and at least one X'd crossmember in the middle with other straight ones in front and behind the motor, and at least one or 2 more in the back. So a total of 3-4 straight crossmembers and one large X'd cross member. Even using the Ibeam, this would have to be rigid/strong enough?? I also plan to not drill the areas where the frame is Z'd, and may even plate those areas on the inside. I am sure it has been done, but I have not seen it. So what do you guys think? Opinions, Ideas, criticisms? Thanks Marc
What motor? I like the idea. Its different, and different is good. As long as it holds up, and isnt unsafe.
I have no say whether or not it is a stupid idea. Im no engineer and have no idea if it would hold up. I do think it is stupid to merely say "Yup" and tell him it is a stupid idea with no validation of your opinion on why it may be stupid. Nick
If my memory serves me right, I think someone here on the Hamb is doing the same thing. Bobbleed maybe?
I have never thought of that as a material. I would guess it would be more apt to "bend" in a fore to aft mode than say rectangular tubing would. It should be [about as strong] in a twist -[say right to left] orientation.... Id suggest asking some of the engineers on the Hamb[maybe Terry-38 chevy454]
i think it sounds cool. buildings are made of i beam. but buildings don't move. i think with good bracing that twisting shouldn't be an issue. i think it will look bad *** though.
I think you should be fine With proper bracing and cross members you should have more than enough torsional rigidity. What motor you plan on using?
hes right there is just way to much flex in a i beam then in a peice of tubing. and the i beams weight exceeds the weight of tubing as well.. it ok for buildings but not for building ch***is just my 2 cents dig deep in your pockets and buy some tubing bill
I beam does not have torsional regidity like a tube (either round or square) so It's not the best material for frames. That said Kustombuilder must be finished with the frame he started so lets get a "real world" report on his findings. Frank
a stock model A frame and most pickup frames use a channel, which is structurally the same as an I beam As long as it's a light weight rpu, not too much power, it should be fine. The frame will be kind of heavy for one with that little strength, but since an rpu is really light anyways that shouldn't be a problem (yeah I'm one of those engineer guys)
It might be 'strong enough' but, I wouldn't use it. I had a friend use channel for an engine stand,and it bent like taffy,when the full load was brought to bear on it. my $00.02Sparky
an engine stand is not the same as a frame! notice the frame has two channels, one on each side, tied together with crossmembers, and the load is properly distributed.
Since when was a rectangular tube frame the standard. . . . . . most frames are channel and an I section will be pretty much the same as channel(slightly better because less likely for the top or bottom flange to distort)
Here's advise from a Welding Engineer.. An I beam is definitely not the same as C channel, and hold very, very different properties than both tubing, and C channel. I beams are used in buildings because they have great strength in the X and Y axis, making it ideal for structural support. However, a frame for a hot rod will be exposed to torsional stress, and if your running any kind of a motor with the design your talking about, the frame is gonna twist like hell, and more than likely, weigh a ****load to boot. A 24 foot lenght of 2x3 tubing shouldnt run you anymore than a hundred bucks, pretty inexpensive insurance if ya ask me.
I don't know if you've ever played with a ladder type (not X braced) pickup truck frame...they have channel side members, and have very little torsional stiffness. there's no difference between a channel that will twist, and an I beam that will twist. A boxed channel or a tube frame member will not twist, true. But tens of millions of trucks were built over the past many decades with open chanel frames, they twist easily, and they last a very long time. I don't see what the problem is.
Just for comparison, FWD, Oshkosh, and Crane Carrier trucks use I beam frames on their heaviest duty truck models. Pound for pound tubing is hadr to beat for strength, but an I beam is in effect, two C channels back to back. Built correctly, it will be more than strong enough.
An engineer friend of mine has been looking into an aluminium I beam frame for a 30s coupe. He is lookinginto using a special I beam extrusion used for the main structural rails in medium commercial aircraft- they are about 5x3. It will be interesting to see how he gets on.
First question I'd ask is WHY? If it's because it is cheap, then fair enough, but box section's not exactly big bucks to buy. Second point is it'll be heavy. Depending on the gauge of the I beam it'll be heavy, or REEAAL heavy. Third point, it'll be twisty as a very twisty thing, like stock channel ch***is. If you boxed just the inside of it you'd have a real strong ch***is, that weighs a ****in' ton, and you'd have wasted time and money boxing it that could have been spent buying ordinary box section tube. Not a good idea, unless you just want the 'shock' value?
Well metal is getting high these days but i got my 24Ft section of 2X3 .188 wall and 3/8 inch plate for a little under 200 bucks (i think 185) so i would go with that my self. By the way have ever seen a big rig take off. Even the ones with I beams twist like crazy they have to or they would snap the frames thats why i beam is used FOR its lack of torsional resistance but extrem weight carring capability. Yes C chanelles have been used for ever. Every body i know who has bulit a hihg powered anyhting but a restoration has boxed them in also. Theres a reason for that. Channels were used cause they were cheap not better. Car makers are considered witht he bottom line not the quality so much.
I agree with Blury, everybody uses c channel frames but they box them to gain strength, Ibeams are designed to twist even an I beam axle twist. I would fear that one it would weigh a ton and two would be extremely flexible. I have had several tube ch***is cars and even those will flex when under torque.........not a good idea, but not a stupid question....my2 cents....RP
Having read all the responses, I'll throw my opinion AND a little fact in the ring. I think it would look cool. I know it would weigh more than it's worth. I know it would twist like a pretzle. A guy at work has '58 Corvette that was a 'Show Rod' back in the late '60s. The front frame is made out of I-beam that has been chromed (BLING!). He recently started a resto on it to bring it back to it's former glory. Being a frame straightening-outter-guy, he brought the front section in to straighten it on the frame rack. What a mess!!! I convincec him to start over and we'll be building a new frame with 2x3 tubing and round x-members. The chrome beam looked cool but did not function well under pressure.
Well,there has been a fair amount of discussion on this and I never noticed this part of it..... Is this free I beam the guy is gettin ,STEEL or IRON? it comes both ways.Still I would recommend some 1/4" thick C channel or box tubing.....
Anyone go to the PILEUP and see that big skull on I-beams, rear engine, 4wheel steering? At least I think it was on I-beams. Who built that thing? Maybe ask him?
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