FRAME, Chassis guys - give me some feedback!

[Ryan]

Okay fellas, I am getting some thinking done on my rear frame 'z'. Since I am going with a spring-behind rear axle I also need to extend the chassis 7" while I am at it (to keep stock wheelbase). So, attached to this post you will find what I came up with... Total drop will be about 7 inches...

My question to you is:

1. Is this a structurally sound idea?
2. Anything I should look out for?
3. Am I dumb shit that is missing something major?

Thanks in advance.

[Winfab]

Make your frame cut at 22.5 degrees or you will end up with a kickup with less than the 3" frame thickness (height) on the diagonal kick section. Draw it out...I think you'll see what I mean.

[Ryan]

That totally makes sense... I knew I was a dumb ass...

[dondanno]

Ryan when you cut your frame cut at an angle no vertical lines the frame will be stronger. I am also going to do the spring behind but no z and will fish plate and box the area. If you have room to fish plate do it, the plate should be diamond shaped with round corners. I messured my spring location and its 7 3/4" so be extra sure. Messure 50 times cut once....Danny

[Winfab]

You're welcome. Only IF you had already made the cut would you be a DA! Ha!

[SamIyam]

Where is the axle in relation to the added piece?
Presferrably it would be under the rear horizintal piece to give you the most clearence... I would also make sure to make a boxing plate that goes on the inside that is the shape of the entire kick up... in other words, there should not be any joints in the boxing plate... also, this may require an odd size piece of square tubing for the kick up... or you might try cutting one of the 3" sides off of a piece of 2"x3" tubing so it ends up a "C" channel... and then box it all in with a piece of 3/16" or 1/8" plate... and... what you have drawn up is going to give you 4" of additional kick up over what it was stock, FWIW.
Sam.

[Kevin Lee]

Alright. Then I AM a dumbass. Here's how I did my vertical cuts and of course there is the picture I show every time someone talks about kicking a frame lately. Only difference is I swapped my bells and REMOVED 7.5 inches.

I don't have the chi-chi labeled diagram you have but all of the basic shapes are there and you can kind of tell how I fit it together. Welded the sides first and then took a hammer and wrapped (beat) the tabs around the outsides (top and bottom) until they met up with the rails. It will have boxing plates that tie into the tubing I used to make the kicks too. Hell, you've seen it - I'll shut up now.

Anybody care to tell me how weak my frame is? http://www.jalopyjournal.com/ubbthreads/images/graemlins/crazy.gif

[C9]

Go here: http://www.airbum.com/NeatShtpix/RoadsterFrameSaga.html

Look at the gusset he did.
Simple, clean and sufficiently strong.
Aircraft methods as noted.

This strikes me as an excellent way to gusset over a "C" notch.
As thin as some of them are and considering the entire weight of the car's rear half is riding on it, sure looks like there ought to be some reinforcement.

Even if the "C" notch is boxed in and closed, that style gusset would be easy to add.

[DrJ]

I'm with what Sam said. the horizontal part "B" that has no dimensions indicated but appears short, needs to be long enough to span from the rear mounted spring to in front of the axle tubes so the axle will clear the upright parts of the "Z".
If the frame's going to be so low that the side rails are lower than the axle, why not run the frame under the axle without a "Z", underslung?

Grimlock,
The angle they were talking about as Ryan drew it would have made tha added in upright piece way less than the height of the frame member. Your's accomodates that situation with the "step" cut you have in your upright. If your weld is as strong as adjacent metal and you fishplate it t should be fine on a light car. Hell, Every Fad T on the road has butt welded "Z"s in the rear.
Do they break?
Most of them are only carrying a 200 pound T body and interior and a 300 pound driver... http://www.jalopyjournal.com/ubbthreads/images/graemlins/wink.gif

[Kevin Lee]

I'm pretty confident everything I've built so far will be fine. I'm of the "looks right, is right" school. Form and function happen simultaniously as far as I'm concerned. The airplane gusset C9 posted is rad.

[Hackerbilt]

I havn't checked it out completely but Budd Davissons AIRBUM site seems to have a load of good information tucked away!
I hope he joins the HAMB...he would be a definite asset.
That little roadster he has couldn't be in better hands!IMHO

The guys nailed all the important aspects of the kickup...
I just wonder if it wouldn't be cleaner to fab it with curved joints, just for extra neatness. Semi 32 style...
Wouldn't be too hard.
I like the fish plating idea. Done Davisson style, it would be totally cool!

Bill

[Dreamweaver]

Ryan,

Thanks not only for the HAMB, but for asking all these questions. I brought the sawzall home from work tonight!

Props to all you folks that have been down this road before and are willing to share.

[Killer]

In plain English:

if you cut a piece of 2x3 on a 45 degree angle, the opening will actually be 2x4. If you cut the same 2x3 piece at 22.5 and the new piece also at 22.5, both openings will stay 2x3...

Ryan, better idea on the kickup that attaches to the original frame (bottom piece). Notch the top of the original rail so you can slide the new piece of tubing to the bottom of the old chassis.

A picture is worth a thousand words here cause I suck at explaining shit but my digital is broken....

[injectedA]

Like this?

[Ryan]

My head hurts... Why can't any of you technical people draw worth a shit?

[sawzall]

ryan..

with somethin more like what grim is showing.. you will have more weld area..and hopefully a better chance at penetration http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

[rickyracer1962]

maybe you should stick to sewing?

[injectedA]

In that pic I posted in reference to Killer's reply, I should have removed the red and blue, as that would no longer apply. That pic was someone elses from here, I changed it. Pretty sure he means to extend thru on the lower as shown.

A lot of you have looked at this thread. Post your ideas. I'm dealing with the same thing.

This is the pic from C9's post. I can't do this as I'm going coilover. But it looks damn nice and strong. I am going to use the single plate idea at my front Z. There's no character up there. Looks cheap. But I think by raising the hgt. of the fin and drilling it. Maybe.

[stevenjerk]

hey saw this on 345window s website check it out

[Unkl Ian]

[ QUOTE ]
Why can't any of you technical people draw worth a shit?

[/ QUOTE ] Make all cuts at 22.5 degrees,this will give you a kick up at 45 degrees.AND maintain the same cross section.

[40Tudor]

Unkl Ian beat me to it, but here it is anyway - matched vs. mis-matched cut angles.

Hmm...too late AND crappy quality... http://www.jalopyjournal.com/ubbthreads/images/graemlins/tongue.gif

[40Tudor]

Another try:

Mismatched angles
http://marley.bitstream.net/~youngc/misc/kick.jpg

What I think Grimlok is up to
http://marley.bitstream.net/~youngc/misc/kickg.jpg

While it's not all that visually appealing, I think the center gusset thru everything is structurally best with the full size boxing plate covering all the joints second best.

As usual in structural problems, it's really a question of what you really need? They'd probably all work effectively for a light car assuming good quality welds. I could throw some FEA at it if anyone is able to estimate peak dynamic load.

Chris

[injectedA]

bttt

[Dreamweaver]

Oh ya!

That 3-d one looks to be the ticket, spreads the load out better. What would be the angles on those cuts?

[rickyracer1962]

bttt

[Kevin Lee]

Yup, that's what I did. It's actually done and welded in. What I did do was leave the inside surface of the tube intact (you can see it in the photo) and am going to lap it over the boxing plate - sort of like a combination between a fitch plate and that airplane gusset. Sounds incredibly sloppy and overbuilt but in reality it's just overbuilt and not very sloppy at all. In fact it should look pretty smooth once it's done. No photos yet. I'll get some film tonight though - no digicam.

[40Tudor]

So, if I understand it right, you have a notch on the outside and just a straight angle on the inside? And the frame rails are cut square? Is the tube that you cut the notches in wider/thicker than the frame rail?

[Ryan]

shit 40tudor, what did you do the 3d drawing in? Would be sweet if the software had measurement capabilities to scale... That would make this whole mess easy...

[40Tudor]

If I assume the answers to all the above questions, here's what I come up with http://marley.bitstream.net/~youngc/misc/kickg2.jpg
http://marley.bitstream.net/~youngc/misc/kickg1.jpg

As far as the angles of the cuts - it really depends on what you want to end up with, but the notches are square cuts with one side cut to match the height of the tube plus a little for the radius. Hopefully the pics help explain it.

The cuts in my pictures were carefully fudged to look kind of like Grimlok's photos and drawing http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif The approach could work for any angle between 0° and 90°.

As for strength - I think it's an improvement over straight angle cuts, but it's hard to argue with airplane guys when it comes to strength vs. weight.

Might be a little better to overlap both sides like injecteda suggested (front and back would look like the 2nd pic above), but, again, there's really 3 things to consider

1. How much strength do you need? ...and I'm not qualified to say.
2. How much does it weigh? ...and do you really care?
3. Does it look good? ...I'm probably not qualified to answer that one either!

Ryan - All my pictures are from SolidWorks. Gimme some dimensions and I'll make you a drawing. I forgot - are you working on an A frame? If so, I'll need the height of the kick, distance from the back of the frame and an angle. If not, I'll need tube sizes and taper info, too.

Chris

[Ryan]

Rad, I will take some measurements tomorrow and get them to you. Off hand, It's an a-frame, I want between 5 and 7 inches of step and I want to extend the chassis 7.5" in the process... Because of a x-member I am using, the step has to begin about 14" from the front edge of rear crossmember where the rail is exactly 3" in height - it does taper there...

More on that software, what is the native file format that thing exports? I've never heard of it...

[40Tudor]

http://marley.bitstream.net/~youngc/misc/framer2.jpg

Did some fooling around with the measurements you gave and my stock A-frame. This is 7.5" back and 7" up with the kick in line with the normal frame taper. I modeled the joint as a 'double Grimlok' cuz it was easier not knowing what the angle would come out to.

I left the stock rail on the pass. side for comparison.

Note that the rear of the frame is now wider by 1.3" or so and the angle of the kick is almost 51°.

If you don't want the frame to get wider, then the cuts on the rails should be perpendicular to the centerline of the frame rather than being perp to the outside of the rails. Everything else would come out close enough for filing and welding, I think.

SolidWorks (http://www.solidworks.com) is a CAD software with it's own native format as well as the 'normal' CAD formats. Just happens to do .jpg and .gif, too.

Hope this is helpful and not too confusing.

Chris

[DrJ]

That's cool.
I like the colors. think I'll repaint my frame!

[Kevin Lee]

40Tudor - That's it. Pretty much nailed it with that second drawing. I think it's going to be one solid mofo.

Ryan - For what it's worth I made everything at 70 degrees - which puts other things at around 20 degrees or so - and of course there's some fudging and grinding for the slope of the rails on the bottom.

Right or wrong 70 degrees just looked better and "stronger" than a straight up 90 or a really shallow Z. But I had more to work with since I was removing frame material.

[Mart]

All good stuff, guys,
Can I make a suggestion?
Make sure the kickup is far enough in front of the axle to allow for radius rod clearance. you can see there is plenty of room in the pic from 345window's site. If the kickup was further back, it might foul the radius rod.
I was lucky on Old Rusty, there was enough clearance, though I didn't plan for it. On the front kickup on the Pop I had to rework it as there wasn't enough clearance.
Mart.

[DrJ]

[ QUOTE ]
All good stuff, guys,
Can I make a suggestion?
Make sure the kickup is far enough in front of the axle to allow for radius rod clearance. you can see there is plenty of room in the pic from 345window's site. If the kickup was further back, it might foul the radius rod.
I was lucky on Old Rusty, there was enough clearance, though I didn't plan for it. On the front kickup on the Pop I had to rework it as there wasn't enough clearance.
Mart.

[/ QUOTE ]

Damn good point Mart.
It only applies if the radius rods aren't split but definitely IMPORTANT!

Another suggestion.
Something manufacturers find helps design development with their their prototype models, (otherwise, why would they spend LOTS of money doing it?) in various scales...
I think it's a good Idea to mock up all this stuff on a 1/25th scale model first. I chopped the top on a model truck with the exact same cuts I was planning on the steel one before actually cutting the real deal.
No I didn't waste rod building time finishing the model.
I still have it in pieces unpainted, unassembled.
I just used the mods on it to confirm that my planned cuts would work.
just use a caliper and your calculator to check the modification measurements.
AMT is pretty accurate.
Buy a few Model A kits and USE them for research!

[Junkyard Dog 32]

This has kinda been bugging me, since I saw it....and I may be wrong. I'd like some thoughts.

This joint (or joints- 4 of them). GRIMLOK- I'm concerned about the crossways welds (in RED in the pic). It forms a shoulder at a stress point. A weld, here, is a potential crack waiting to happen.

[Junkyard Dog 32]

Here's a quick thought on frame "stretch". I just made up th term, but it fits.
Under acceleration, the rearend wants to spin (upwards in front). That pushes forward on the radius rod, and thus, the frame. Add that to the already pre-loaded (weight of the car) frame, and those joints want to "straighten".... the upper rear, especially.

[40Tudor]

[ QUOTE ]
This has kinda been bugging me, since I saw it....and I may be wrong. I'd like some thoughts.

This joint (or joints- 4 of them). GRIMLOK- I'm concerned about the crossways welds (in RED in the pic). It forms a shoulder at a stress point. A weld, here, is a potential crack waiting to happen.

[/ QUOTE ]

Not only is that an area of high stress, but there's a weld there in every common type of joint I can think of - not just Grim's. Best bet in all cases is to reduce the stress overall (by adding a center rib or overlaps, etc...)

As was mentioned above, you also have to leave enough clearance for radius rods, etc..."damned if you do, damned if you don't" http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif

As my welding instructor told me many times, "A good weld is at least as strong as the base material". No cause for concern if your welding technique is good. This is where fishplates and overlaps help - they reduce stress in the joint as a whole.

Chris

[SamIyam]

[ QUOTE ]
Here's a quick thought on frame "stretch". I just made up th term, but it fits.
Under acceleration, the rearend wants to spin (upwards in front). That pushes forward on the radius rod, and thus, the frame. Add that to the already pre-loaded (weight of the car) frame, and those joints want to "straighten".... the upper rear, especially.

[/ QUOTE ]

I think we went through this before with Harlan-book-smart... but when you anchor the rear wishbone in more than one spot... and then the rearend (or front end) with the spring in another spot... that radius rod/hair pin no longer just forces in the forward direction...

Anyway, I think most of these are sound designs... not neccasarily pretty, but sound enough to hold up under most driving conditions... so, weld away.
Sam.

[Junkyard Dog 32]

I agree... There's alot of cars with Z'd frames, and you don't see them broken in half all over the roads. I'm sure every one has a different layout. The body/body mounts act to strengthen the whole thing, too. It's just, as a repair welder, I know what breaks. After all, it IS only steel... http://www.jalopyjournal.com/ubbthreads/images/graemlins/grin.gif
I can see GRIMLOK put alot of thought and effort into the job, and I don't wanna piss on his pillow. That might be the strongest joint in the history of hotrodding... That's why I asked.

I guess I'd still like to see a plate, at least on the inside corners... (don't weld the ends...)


JOEhttp://www.jalopyjournal.com/ubbthreads/images/graemlins/cool.gif