I hope this is the right spot to ask this, but I'm building a frame for my 27t, the car will have a 4cyl but eventually a v8. My question is the frame is 3x2 steel box .120 wall. For the cross member I can get some 2.75 .125 wall erw tube, I'm worried it might be a little thin and I need some opinions.
Since you're using tubing, .125 is plenty. It'll be stronger and stiffer than the channels Ford used in the T and the A.
Actually if you do a search for "frame building" , you will get 20 pages of great information to help you ! Retro Jim
I searched but really couldn't find something that was exactly what I needed. I'm just worried about the front and rear crossmembers being 2.75in .120 wall. Also it will be a suicide axle.
I know the box is plenty thick, I'm talking about the thickness of a tubular front crossmember. Not box, I searched and couldn't find an answer.
Unfriendly, essentially tube is "boxed"! Whatever the configuration, it does not have an open side. The open side is what causes weakness. ~Alden
Ok good to know, plus I read making it thicker won't make it stronger shear wise, but increasing surface area will. Thanks for the help, ill post a build up soon.
Thanks that's exactly what I wanted. That's a good read btw, now I need to think of how to do my x member.
The HAMB 'search does not work very well. Some of the guys suggested that using Google with your search term plus HAMB works good and it does
The 3x2 x .120 rails are great. The 2.75 x 0.125 crossmembers could be great but that depends on how you attach the brackets and such. Thought should be not to count on the 0.125 wall thickness but the strength of the tube.
Well as far as brackets I will have a suicide set up in the front with the spring bracket on top of the tube, and a 4 link rear which will most likely go too the frame rail and x member.
Seems to me you're building your frame to the bare minimum requirement. In an honest, street driven car, you can't use a thinner/smaller rec tube or a thinner/smaller crossmember tube than you're planning. Personally I'd be going with at least a thicker (3/16) 2x3 and a thicker/larger dia front crossmember as well...BUT I'd more than likely upsize to (3/16) 2x4 if I were tapering the rails. The frame is THE ONLY structure you have in a T bucket and all the weight is pressing on the middle for the most part. Whatever floats your boat I guess... Personally I like a wider safety margin than your plans will offer.
3/16 is way over kill, hell a city bus frame is only 3/8 steel. Think of the 2.75 .130 wall pipe, shrink it too 2.5 it would increase the wall thickness. From what I've read and talked to people about a 1500lb max car would be fine on a .125 wall frame, especially it being boxed and having a roll bar like i plan.
I bought the download of this the other day and it is well worth the price for the info it has along with the tips and diagrams that are in it. http://www.tbucketplans.com/california-custom-roadsters-t-bucket-chassis-plans/ There is a ton of "oh shit I didn't think of that" stuff in there that will help a guy either build a better and better looking frame or solve a question he has.
It's only 1/16 thicker than 1/8 and allows you to tap directly to the frame for line brackets etc...besides offering some additional strength. WAY overkill...I think not. Besides, the real additional strength would come from the extra inch of depth with a 4" tube. City busses have a full body as well to give strength...and besides, 3/8 is huge thickness! I look at a T as more like a pickup. The only thing giving it any strength IS the frame. (The body on a pickup being divided between the cab and box.) Roll bar won't do anything to help beyond its attachment points...unless you mean to put something like a 12 point from front to rear! (And I hope you don't! LOL) Regardless, I still think you're building it to the minimum standard required. BUT thats just MY personal opinion! YOU...just need to satisfy yourself, be safe and have fun! You're happy....I'm happy too!
Well I do plan on making a tubing "structure" inside the body, but hidden by interior, so with that and the frame I should be plenty fine.
I just opened up the pfd for the set of plans that I posted the link to above and they do suggest .188 wall thickness for the main frame rails.
I am frequently perplexed by the folks who ask for opinions about what they have planned........and then when they get an opinion from experienced people contrary to their preconceived notions.....spend lots of time defending their original plan. Makes me wonder why they asked in the first place. In case my point is too subtle, the OP seems to fit in this category. Ray
Check out the roadster in my avatar. 2x3x .125 wall. Frame was built by me using dimensions for a model a frame from the Tex Smith book how to build real hot rods. It fit the 27 roadster body better then the model t frame. Small block chevy and 350 trans. I have driven it for four years now with no issues.
If you think 3/16 is overkill it does seem you already made up your mind so why are you asking? Overkill is not a bad thing, better overkill the under and killed! .120 wall would probably be ok, lots of cars built that way. Still at our shop (a pro chassis shop) we only use .120 wall if it has a full 12 point cage to prevent twist and flex. Note I said cage and not a roll bar. Any bucket or Model A frame we do is 2x3 3/16 wall. Not enough weight/ cost differance to be an issue on a street car and your body will hold up better, especially if it's glass. Frame flex is hell on a body, steel cars it chips the paint on jams, pretty soon door don't close right, ect. Glass cars end up with stress cracks in no time. I personally also like the more rounded edge of the 3/16, looks wise but maybe that's just me. On the front C/M. I would suggest at least .134 wall on any C/M that supports suspension, it will hold up better to the constant twisting motion the suspension causes. Bottom line unless you are building a race car where weight is a factor why not build it a little stouter?
I always prefer 3/16" for this type of frame, many advantages as mentioned over 11 ga with very little increase in weight or cost. I also like to use 1/4" wall round tube for the front crossmember when using a suicide perch. Maybe overkill, I just feel it's common sense.
HaHa , I agree here ! I am also frequently perplexed , but mainly with the judgement made by people who give an answer but their "ego" won't let go because the person asking is seeking different answers [ or a confirmation that they are not already making a mistake ] No such thing as stupid questions, maybe stupid answers! I've been in a similar situation with many innovative ideas seeking solutions, then I get bombarded with "this is how we did it years ago" type bullshit answers. Or "Cowshed Engineering" type mentality [ Build it Heavier,then it will be stronger!, or "She ain't broke so don't fix it' ] Traditional hotrodding was about making cheap innovative improvements , not following the "Status quo" with the "silver weeny syndrome". In fact if history isn't too distorted with exaggerated war stories I believe hotrods were stripped down to become lighter in weight The "Poms" taught the whole world a lesson about innovation during the early 60's with their grand-prix cars [ With Rear Engines, Space Frames, Then Monocoques & Semi Monocoques ] What they did was the "Same Shit Different Shovel" method of stealing ideas and applying it to a different application. Back to a T Roadster frame, I personally would prefer 100 x 50 x 2mm wall [ 4x2 x .083 ] over 75 x 50 x 3mm [ 3x2 x .125 ] it would be lighter and have stronger beaming strength. But over here in NZ I cannot buy a 2mm wall section RHS .120 wall is plenty strong enough, In fact original Ford stampings were about .120 for a "C" channel section, hotrodders have been boxing them to make RHS but it is generaly not neccessary to do this [ a flathead V8 weighs more than a SBF and slightly less than a SBC ] Generally stiffening of the frame is needed to counteract the suspension resistance being increased, if the engine put out more torque it loaded up the suspension more The moment of inertia of a 3"x2" x0.125" RHS 1.41 in^4 A 3000lb force, in the center of a 108" span or in this case Wheelbase [ divided between 2 frame rails ] is about 3/32 of an inch deflection each Check out this thread , here is a T roadster with a space frame incorperating the body, it shows a bit of innovation and creation http://www.jalopyjournal.com/forum/showthread.php?t=685236&highlight=kiwi
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