I'm going to just build a frame from scratch, and have been doing a lot of searching for guys that have built frames. I'm pretty much set on the 3/16" wall thickness, and am also pretty set on using 2" wide box tubing, but have been going back and forth on whether to use the 4" tall or 3" tall.

I plan on doing something very similar to what Iismp (sp?) did with his TJ frame a while back, meaning 6 or 7 cuts to allow room for the axles with some 1/8" steel plating over the cuts. My thought is the 3" tall will be lighter obviously than the 4". My reasoning for the 2x3 box tub vs round tube is it's MUCH easier to weld bracketry since I won't have to notch everything, plus I don't have a bender, and don't care to buy one. I've got a buddy with a nice one that agreed to help me do the cage and tube work, but asking him to use it for the frame is just too much. So can anyone talk me out of using 3" high box in lie of 4"?

I just used 4" because it was close to what was on the original frame. 3" would be less weight though. That was my only reasoning. Go for it!!

I am planning on building my own frame. I am going to use 2x4x3/16 only in the middle straight-ish section. Then go to 2x3x3/16 on both ends from the transitions out.

Have you looked to see what the strength differences are between 3'' and 4''. That would be my deciding factor. You would need a tube that at worst case is stronger than the factory frame. I am sure if you are doing a custom build...you are going with at least 60's and a V8. I am sure you have already thought about that but just making sure.

How do you plan to transition from the 2x4 to the 2x3 out of curiosity :grinpimp: As for the strength factor, the factory fram is 1/8", i figured 3/16" 2x3 is stronger than 2.5x4" 1/8" factory frame..but it's a guess?

After having built a frame out of 2x4 3/16 I can say for sure that I'd never build another one that thick, it just isn't needed. I'd probably do 2x4 .120 and it'll be every bit as strong as the stock one (as long as you're a good welder), and I'd also skip the plates on the sides if the cage is tied into it. One way to look at it, how many buggies built from .120 wall tubing have plates over the joints....

I'm using 2x4 1/8" I think 3/16 is overkill and alot of extra weight for nothing. I might add a couple short strips of 1/4 or 3/16 to the bottop of the frame to drill and tap for skidplate mounting and thats all the extra thickness I'll be using.

Really, you guys would go with 1/8". When i stretched my old YJ, i cut the frame behind the front seats and used 2x4 1/8" tubing and just welded 1/4" plate on each side to butt up to the existing 2.5x4 frame. I was also wondering about the plating of the joints. I seem to get mixed reviews. My thought was going with the thicker 3/16" square tubing i'd be able to possibly get away from plating the joints, but i'm hearing that even with 1/8" i shouldn't worry about it?

The factory frames are 1/8. Build it from 1/8 and plate the joints with 1/8. Why have all that extra material (i.e. dead weight) in the rest of the frame?


Lighter is better.

ok so i go with 1/8" now does that rule out the 2"x3" square tubing since i'm already going with a small 1/8" wall thickness

I used 2x3. If you plan to tie the cage into the frame then strength is meaningless. 1/8" is more than adequate. Just weld in some foot plates wherever you plan to weld link tabs, cross members, etc...

THANKS Tennycar, i've been following your build, and plan on building a very similar set up. What do you mean by "footplates" where i'm going to weld tabs? Also, i was planing on bolting both f/r crossmembers in for the susp links

I bult my frame out of 2x4x 1/8 and the rear I went to 2x2x1/8 and tied the cage to for extra strength. I used 3/16 gussets on all my cuts. 3/16 is over kill and to much weight

If you look where I welded in the cross members for the links I welded in some 3/16 plate in a large area where the cross members would weld in. the problem if you don't do this is that the cross member will eventually rip clean out of the 1/8" plate it is welded to. The entire frame doesn't have to be thick, it just needs to be thick where you weld to it. Hope that helps.

is this to replace an existing frame? or as the base of a tube chassis? if it is just build it out of tube.

my buggy has 2x4x3/16" frame rails and they're heavier than hell. it does make welding to it, etc a little easier on the mind, but as many have mentioned with a cage on top of it 3/16 is probably too much.

good luck,
Paul

is this to replace an existing frame? or as the base of a tube chassis? if it is just build it out of tube.


COMPLETELY NEW FRAME, but i have NO desire to work with round tube, i feel square tube is just easier to work with, not to mention the lack of a bender. So i'm leaning towards the 2" x 3" x 1/8" square tube with 3/16" plates welded in where the motor mounts and crossmembers are based on what i'm reading.

You're set. Get on it!

Sounds like your on the right track, now hop to it, I will be doing the same! (Don't forget to post pics!)

thanks guys, 2x3x1/8" it is, and yeah i'll post pics, it's going to be a few weeks till i get the steel and get all the measurments drawn up, then i'll start cutting and welding with pics to follow:D

Man I forgot to get back with you about going to billings. Is this for your 1 ton tj? My plan would be to use the 2x4 for the low section then where the first bends (or pie cuts) are square, up and butt weld the 2x3 with some 3/16 plates to help hold it. If the 2x4 is cut true square on the end. The cut angle on the end of the 2x3 is almost four inches where it would weld to the 2x4. Then just do your pie cuts as normal for the rest of the transitions in the 2x3. I'm glad you posted this cuz I was really planning on using 3/16s for mine too. I dont want my flattie buggy any heavier than it has to be.

Another vote for .120 wall... I'm going to rock some 2x3" (as long as its actually cheaper) instead of 2x4" for my rig

Playing devils advocate here, 3x2x1/8 weighs 3.89 lb/ft while 3x2x3/16 weighs 5.59 lb/ft Figure the FRAME ONLY will be roughly 32 lnft. The 1/8" frame would weigh in at 125lb/s while the 3/16 wieghts 179 lbs. We're talking a difference of roughly 54lbs, then i'll need at cut and weld at least 10lf of 3/16" plate, 3" high at the motor mounts and cross member. Is that worth the added effort to go back and plate the cross member and engine areas?

Bear with me cause I'm a nerd, (math major) but 3/16 plate weighs 7.66 lb/sqft. At 3" high it's .25 sqft (3/12), I take the 10lf x .25 = 2.5 sqft of 3/16 steel x the 7.66 lb/sqft to total roughly 19lbs of added 3/16 plate to the frame, subtract that from the 54lb's I'm saving by going with 1/8", I'm really only saving 34lbs and have created quite a bit of extra work cutting and welding the 3/16 plate in to save 34lbs.....I"ll get back to work now...just thought i'd throw that out there to ponder :flipoff2:

And just for reference, since i have my steel book in front of me :grinpimp: the 4x2x1/8 weighs 4.70 lbs/ft and the 4x2x3/16 weighs 6.87 lb/ft, making a 3/16, 4" frame weigh in at 220 lbs.

That makes 2x3x3/16 look alot more apealing to me. My sammurai has 1/8 inch 2x4 box from the factory. It definately rips apart easy just scan through the zuki page. So for me I think I will stick to 3/16 wall.

Personally, I would opt for the 3/16 (maybe just for the thickness/torsional rigidity).....and go on a diet! By your calcs the difference is minimal and if the COG is low enough it may also be helpful.

It may be overkill....but what isn't about our projects. I think it'll save time from additional bracing and having to add backing plates in certain areas. Although, I suppose you could use .125" for your plating.

EDIT: Just a thought...but depending on your number of crossmembers planned (torsional rigidity) most stock frames are of the 1/8" range....I know not exactly apples to apples here. Many stock frames when subjected to the useage we expose them to have frame crack issues (I don't think they were meant to be wheeled often). Again, I would opt for the 3/16" to try and eliminate frame flex....then obviously build flex into the suspension. I know the cage will stiffen it up, but that will also depend on your cage design. Just food for thought...or thinking out loud. You have a small frame project (relative) and the weight between the two as you noted is not that much different.

I'm pretty anal about weight and will use as thin a material as I can and build structural integrity into the car to keep it rigid, but that's me. I like to weld and be somewhat artistic with plating so that is the route I'd go. If you don't really care about the extra weight savings, don't enjoy welding, or detail metal work then the 3/16 is faster and probably more up your alley.

TeenyCar i LOVE your work but in my case, i think the 20lb's of savings along with the added work necessary to use the 1/8" makes the 3/16" a more desirable choice for this particular application. Plus i plan on beating the living snot out of this rig, so a little extra beef won't hurt. I do plan on running the 2" 7075 aluminum links with some 2.5" jonny joints at each end...so that should save some weight and get me strength

i agree with you, that is a whole lot extra time to be spent cutting and fitting and welding...

the frame will be below your COG so the added weight isn't really the end of the world. it just all adds up and takes a toll on your axles later...

awesome thread i had this same question. thank goodness for searching. this is the best info ive gotten yet. i tried to make a 2x4 by 1/8 frame about a year ago. but i was totally unprepared. this info is much better. good thread wally.

Aaron
oh and thanks for going into the math. i lost my steel book which sucks but more than appreciate more the a guesstimate on weights. sweet thanks again all

A lot of the need for plating will be dictated by how you design your mounts. If you use a piece of tubing coming from the motor mount to the frame, and weld it in the middle of the 4" side of the frame, you'll obviously put different stresses on the frame than if you'd come off the frame with plate up to the motor mount, that comes off the entire side of the frame (easy to visualize, difficult to explain). For the tranny crossmember if you have a channel that goes around the frame and bolts horizontal through the frame, you also wouldn't probably need plating there.

My main point is that you can design the frame so it doesn't need all sorts of unnecessary plating. For what it's worth, my frame is 2x4 .120 wall tubing with butt welded joints (unplated) and the cage tied into it, and it is plenty strong for a SBC, one-ton's, and 42's.

Wally... do you plan on building this rig at my place... cause theres NO WAY IN HELL youre gonna be able to do all this shit in your garage.:flipoff2:

Wally... do you plan on building this rig at my place... cause theres NO WAY IN HELL youre gonna be able to do all this shit in your garage.:flipoff2:

Another meth-a county resident.
Clemson, Wally you guys want to go run billings tomorrow? Sunday the 18th of nov 07?

I'd go 3/16.

I’m reviving this today because I’ve decided to go a bit of a different direction and will be building the frame this weekend, so tomorrow I’m picking up the steel. Weight is a concern with this rig, I don’t want to be a fat overweight pig like BamaSahara trying to find ways to go on a diet after my rig is built :flipoff2: but the real change is I’ve decided that I’m going to weld the frame/cage together. I plan on running a piece of 1.5” .120 tubing from the front for tube fenders, which will go down to the boatsides under the door and wrap around as a fender protector in the rear before tying into the frame at the back by the tail gate. I feel this should add some significant rigidity to the set up. This makes me think the 3/16” is just plain overkill, esp if I build a hoop/cradle under the motor tying the motor mounts together….so I’m back to thinking 3”x2”x1/8” is adequate.

Wally, just remember what heppened to your last 1/8" wall frame. 20 lbs to prevent that from happening is worth it in my opinion. Not being an engineering nerd, I'd like to know the resistance to bending difference between the 2x4x1/8 vs the 2x3x3/16". My uneducated guess is the 2x3x3/16 is probably going to be a bit less due to its dimensions, so tieing it into the cage is going to be necessary anyway, not an excuse to go thinner.

You've already trashed one frame, take the steps to avoid it again, save weight somewhere else, hell, you could almost loose 20 lbs grooving the crap out of the tires.

Wally, just remember what heppened to your last 1/8" wall frame. 20 lbs to prevent that from happening is worth it in my opinion.

I agree, i just keep hearing from other people that i'm going way overboard doing 3/16"...i want beef so i don't have to worry about it. It's roughly 50lb's of weight savings by going with 1/8" vs 3/16"....we'll see i'm going tomorrow to pick up the steel so by 3:00pm MST i'm commited to one direction or the other:eek:

I agree, i just keep hearing from other people that i'm going way overboard doing 3/16"...i want beef so i don't have to worry about it. It's roughly 50lb's of weight savings by going with 1/8" vs 3/16"....we'll see i'm going tomorrow to pick up the steel so by 3:00pm MST i'm commited to one direction or the other:eek:

I think you just answered it yourself?

Only a 50lb weight savings....and you won't have to over-engineer the additional support via cage design to compensate for the 'lesser" frame thickness. I'd go 3/16" and save weight elsewhere......as in cage design which is higher up possibly raising your COG........do YOU need a diet?:D

What about $$$ difference? Steel is pretty pricey right now. Where did you get the info on the steel ie: weight per foot. Great info.

What about $$$ difference? Steel is pretty pricey right now. Where did you get the info on the steel ie: weight per foot. Great info.

I work as a construction estimator so i've got quite a few steel manufacturing books to calculate steel weight....i price steel by the ton, so when i estimate a 100,000 sqft building there's multiple steel beams, columns, angles, contection plates etc...also kinda helps when building a rig :smokin:

As for the cost difference it's about $40 or so from what i recall, definately NO MORE than $50

Lots and lots of comp buggies running around with 2x3x.120 frames, and they're not destroying them. Since you're planning on welding the cage to the frame from the get-go, there is no reason not to have it be "structural".

Lots and lots of comp buggies running around with 2x3x.120 frames, and they're not destroying them. Since you're planning on welding the cage to the frame from the get-go, there is no reason not to have it be "structural".

A comp buggy is also light and has alot more freedom when it comes to designing a cage that goes all the way from front to back on the frame rails. If I remember correctly, Wally has an almost full YJ tub to use and has to fit the cage within those confines. Whole different ballgame using a tub vs just hanging skins on a tube buggy. He managed to destroy the stock frame on his last YJ, hate to see him put alot of time and effort into the new rig just to have the same thing happen again.

Well just got back from the steel yard, i ALMOST grabbed the 1/8" cause it looked plenty strong, but i stuck to my guns and went with the 3/16", got 4 10' sticks, and HOLY SHIT is that stuff STOUT...and rather heavy...but i'll live, i feel good about. Build thread should start here in a few weeks after i get the frame built this weekend i'm going to drop the motor in and start taking pics and posting up. Thanks again for the input fellas :beer:

FYI with my general contractor discount the total for 40' of 3" x 2" x 3/16" was $88.00 :D

Shit....good deal. I've subscribed to this thread, I want to see details of the build....good luck.

damn thats way cheaper than the 150 i paid for 24 feet of the stuff from dencol, and i thought i was getting a deal, do you get that for all types steel? like 1/4 in plate, i'm going to go dirtbiking in moab next weekend and i was wondering if you can get deals like that easily if i could order some through you? no worries if you cant but that'd be ultimate, i just finished my frame made of the same thing, and have the body hard mounted as well, i will be building the rollcage into the body and frame so that i can keep the full bodied look, it gonna be sweet to see how you do it. goodluck! pm me if steel is easily available, thank wally

Pretty certain that was just a one time favor on the cost. The contractor i work for is the largest one in Grand Junction...so i tend to get a little love now and again around town...but FOR SURE do not want to take advantage of a good thing :D

Damn yeah i figured as much. thats an awesome price and i look forward to seeing the progress your new project, good luck

so do you have any progress?

so do you have any progress?

Nope spent the weekend in Vail enjoying the 4 FEET of snow they got his week :eek: Might have a chance to start something this weekend, but i'm off to the Carribean later next week so realistically, it wont be till mid feb before i post some pics...don't worry i'll do a new build thread like all the other cool kids on this board :flipoff2: I did just reload all the pics on my old build thread from 2 years ago...the site i had em on went down about a year ago and i never bothered to update em:shaking:

think maybe as you build the frame you could post up some drawings with dimensions? seen lots of great ideas on here but nothing that has some numbers on it.

thanks

trev

i made mine out of 2x4x.125 for the main section and 2x3x.125 for the front and rear seactions.

i too debated between .125 and .188 wall.

.125 ended up being 88.5lbs lighter, which doesn't sound like a lot but that is the same as my trail tools and spares.

i'm building a low power (tired 4.3) smaller CJ2a rig, so .188 was a bit overkill.

.188 isn't going to hurt anything other then a little extra wieght, so build what you want

if i were to do it again i'd widen out the mid and rear sections like a modern heep, my flipped D300 JUST fit between the rails without rubbing the inside of the drivers rail.

http://i99.photobucket.com/albums/l317/owlman999/frame.jpg
http://i99.photobucket.com/albums/l317/owlman999/DSCF0005-1.jpg

Since you went with the 3/16, will you still fish plate your joints or just bevel and weld? I think the 3/16 was a smart longevity move. Just my opinion.

Since you went with the 3/16, will you still fish plate your joints or just bevel and weld? I think the 3/16 was a smart longevity move. Just my opinion.

you should always fish plate a butt-weld

I would agree.

Since you went with the 3/16, will you still fish plate your joints or just bevel and weld? I think the 3/16 was a smart longevity move. Just my opinion.


I plan on just beveling the edges before i weld them up and running a good solid bead with no fish plating. There will be a total of 6 cross members on the frame tying it together. 1. front bumper 2. the motor mount craddle 3. front susp lower link mounts 4. tranny support 5. rear susp lower link mount 6 rear bumper. On top of that, the i will be bendining tube to following the lines of my dovetailed tub so it will be welded at the rear bumper, the boatsides, and front tube fenders, so i feel confident that it will be fairly ridgid and tied together adequately, eliminating the need for fish plating. I'm sure there are plenty that will disagree with me, but in my opinion, if the connections are properly beveled to 45* allowing for good penatration, and plenty of fill material, combined with the cage being welded to the frame, should provide more than enough support/strength.

I'm off the Carribean later this week for 10 days, so i won't be posting any progress pics for a few weeks.

That 10 Day trip is getting close to a 10 month trip. I am in need of a new frame for my CJ2A and want to build my own. Any updates on your progess?

That 10 Day trip is getting close to a 10 month trip. I am in need of a new frame for my CJ2A and want to build my own. Any updates on your progess?


Yeah i started a new build thread here (http://www.pirate4x4.com/forum/showthread.php?t=672771) but i haven't updated it in 2 weeks, i'm hoping to get over there the last week of Sept to start in on the tub, but it's tough living in an apt waiting for my house to sell with the rig 45 miles away.

I used 2x3. If you plan to tie the cage into the frame then strength is meaningless. 1/8" is more than adequate. Just weld in some foot plates wherever you plan to weld link tabs, cross members, etc...
x2