nitrous nut
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hand built frame has a lil bounce and lil bow. is this a bad thing?
lil bounce in the frame ?
- Thread starter nitrous nut
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Unkl Ian
Allergic to Idiots
What size material did you use ?
How heavy is the engine and trans ?
How heavy is the engine and trans ?
nitrous nut
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its 2"x3" 3/16th wall. the motor is 350 350
Frame Bounce
It looks like your frame bounce may be due to your front suspension set up, it may also be coming from a flex point on the side rails where a cross brace is welded, say from the engine or tranny mounts forward.
It looks like your frame bounce may be due to your front suspension set up, it may also be coming from a flex point on the side rails where a cross brace is welded, say from the engine or tranny mounts forward.
dmw56
Busted and Rusted on Route 66
Do you have any crossmembers in the front? That is quite a long span in the front there. Are your motor mounts angled out towards the frame, the weight of the engine can cause it to spread the frame. Maybe a combination of these things are making it bounce around.
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nitrous nut
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yes the motor mounts are angeled but i have a cross mem. about 8" in front of them. the trans cross mem. is 2"x2" welded in
nitrous nut
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here is a early frame pic to see the cross mem.
redrider
Active member
Not sure about the bounce in the frame but I do like that you are representing Old Dixie in the back ground.
Had a fairly long post I accidentally deleted before posting it - DOH!
So in brief, my armchair engineer .02$. Bounce is bad for steering geometry (and may be dangerous) and bow could become permanent. How much bow? Do you have the static and dynamic load ratings for that tubing? You have a very long front to back span with no up-down bracing. Cross members help with twist, side bow, and flex in cornering. You need trusses, beefed up rails, or more rails. X cross member would help. trussing the Z would help a bit. A cool truss from the front axle area to the cab area with hole plate or webs could be functional and good looking. A 4" truss even a 1/4 length of the frame may be enough.
Lightning has some good points. That front end 2x2 may not be enough. 1/2 the front axle weight is on the front springs front mounts and that extended 2x2. Check for a single (or two) flex point or a gradual bow the length of the span.
So in brief, my armchair engineer .02$. Bounce is bad for steering geometry (and may be dangerous) and bow could become permanent. How much bow? Do you have the static and dynamic load ratings for that tubing? You have a very long front to back span with no up-down bracing. Cross members help with twist, side bow, and flex in cornering. You need trusses, beefed up rails, or more rails. X cross member would help. trussing the Z would help a bit. A cool truss from the front axle area to the cab area with hole plate or webs could be functional and good looking. A 4" truss even a 1/4 length of the frame may be enough.
Lightning has some good points. That front end 2x2 may not be enough. 1/2 the front axle weight is on the front springs front mounts and that extended 2x2. Check for a single (or two) flex point or a gradual bow the length of the span.
nitrous nut
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thanks guys. i dont think the 2x2 up front is the prob. it looks like it bows in the middle of the frame.
what do you think about a 3" wide by 1/4" thick steel to run down the hole frame front to back welded to the outside of the rails.
Sam_Fear i like your web truss idea
btw the frame is only z-ed in the back the front is flat.
what do you think about a 3" wide by 1/4" thick steel to run down the hole frame front to back welded to the outside of the rails.
Sam_Fear i like your web truss idea
btw the frame is only z-ed in the back the front is flat.
Frame Problems
From the pic of your frame, it looks like you have a lot of open space between the front cross brace and the Z - - a diagonal brace in the Z area will help with the bow and bounce, but a piece welded the length of the rails on the outside will still allow the bow, as it will bow also.But the way you have your front springs[in a reversed arch] to your axle looks like the problem in the bounce -There is no limit to the upward travel of the axle and what do you have for shocks? -Do you have the springs shackled or are they solid mount?There is a free load in the springs[no weight or load] and with them reversed they flex in and out of a load and a negative load[bounce]compared to the rear leaf spring mounting where the springs are under a load.I hope this helps ya out.
From the pic of your frame, it looks like you have a lot of open space between the front cross brace and the Z - - a diagonal brace in the Z area will help with the bow and bounce, but a piece welded the length of the rails on the outside will still allow the bow, as it will bow also.But the way you have your front springs[in a reversed arch] to your axle looks like the problem in the bounce -There is no limit to the upward travel of the axle and what do you have for shocks? -Do you have the springs shackled or are they solid mount?There is a free load in the springs[no weight or load] and with them reversed they flex in and out of a load and a negative load[bounce]compared to the rear leaf spring mounting where the springs are under a load.I hope this helps ya out.
When I thought of a truss, I was thinking the tall end at the cab tapering down to the axle - Rethinking that, I think that it might need to be reversed to work well, and then wouldn't be as eye pleasing.
I'm thinking 1/4 the entire length may be overkill. I bet you really only need to beef up the length between the angle bracing. And if that's the case, you could do it on the inside of the frame (red) and keep the outside clean. Or, again, I think an X brace (green) might do the trick.
Keep in mind I'm just a hack throwing ideas out with no real hands on frame experience - so my .02$ is worth just that. Hopefully someone experienced can set us both straight.
I'm thinking 1/4 the entire length may be overkill. I bet you really only need to beef up the length between the angle bracing. And if that's the case, you could do it on the inside of the frame (red) and keep the outside clean. Or, again, I think an X brace (green) might do the trick.
Keep in mind I'm just a hack throwing ideas out with no real hands on frame experience - so my .02$ is worth just that. Hopefully someone experienced can set us both straight.
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Unkl Ian
Allergic to Idiots
2"x3" is a little small, even with a short wheelbase.
Beg to differ on that one. It's called 'sistering' in the home construction biz and is a common way to stiffen a floor with weak joists - nail new joists to the side of the existing ones. You would have to straighten the frame before welding though or you'd lock in the bow.
As for the front end, I still agree with Lightning, but first things first, fix the frame bowing problem and see where that puts you.
nitrous nut
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i cant put an x in the frame as my motor & trans sits to low in the frame.
i could do something like this if it do anything to help.
the red is the welded trans member
the back kick up has the angle brace in already just not in pic.
thanks for the help you guys rock
i could do something like this if it do anything to help.
the red is the welded trans member
the back kick up has the angle brace in already just not in pic.
thanks for the help you guys rock
Right you are Sam - sistering will add strength,but alone, won't it eventually flex and bow with all of the lateral torsional twists from the engine? Your idea of a X brace in the middle of the frame would help a lot, there is just to much open area there.It looks like the spring perch's are "sistered" to the front of the frame rails,capping the ends will help in the twisting and strength. But before any thing can be fixed, the bow has to be taken out, then contend with the front end.
Nitrous - - maybe some short angle braces out of the 2x3 tubing in front of and in back of the trans cross brace and some angle braces from the cross brace in front of the engine mounts back [just like you have at the front and rear of the frame] Just try to break up the big empty spaces. What type of front axle are you running is it a truck or a trailer axle? it looks like a square tube in one of the pictures.
nitrous nut
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the front axel is home built from a 87 jeep 2wd. i cut the c's off the tube then retubed it with 2"x2"x1/4th wall square tube
Not just engine torque, but uneven road and corning can cause serious frame twist. Sistering will help with twist also, but another cross-brace would help a lot more twist-wise (together that might me enough). An X brace will stiffen both front to back as well as side to side. I would think that front crossmember is stiff enough to handle almost any sideways torque on the front end.
Again, I'm not even talking about the 2x2 part right now.
There was a newer member here that has access to a Static/Dynamic Load Calculation Program - that could be handy.
Again, I'm not even talking about the 2x2 part right now.
There was a newer member here that has access to a Static/Dynamic Load Calculation Program - that could be handy.
