Printable Version | Subscribe | Add to Favourites
New Topic New Reply
Author: Subject: Deflection after welding
Padstar

posted on 9/11/12 at 08:21 AM Reply With Quote
Deflection after welding

I have just finished welding my lower frame and whilst it was done in a jig and clamped down there seems to be a bit of deflection. This is mainly towards the front of the frame where there were some larger welds causing the most heat. It has resulted in the front (engine bay to nose cone) section curling up somewhat.

When the frame is sat on a flat surface and weight applied it sits flat. Will this all rectify itself when the rest of the frame is fabricated and the loads of the engine etc applied or should it be dealt with now. If so what is the best way to go about it?

View User's Profile View All Posts By User U2U Member
Peteff

posted on 9/11/12 at 08:53 AM Reply With Quote
When I built my chassis the bottom had a bit of a bend in it after welding so I turned it over, rested the front on some 4x2 and strategically jumped up and down on it. It worked fine





yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

View User's Profile View All Posts By User U2U Member
Padstar

posted on 9/11/12 at 08:55 AM Reply With Quote
Thanks. That is exactly what I was planning for the weekend!
View User's Profile View All Posts By User U2U Member
Davey D

posted on 9/11/12 at 09:43 AM Reply With Quote
If your jig is steel, and you have an oxy/propane set, then i would tightly clamp your chassis back in the jig to pull it back straight, then warm up the areas that have pulled with an oxy/propane set, then let it cool down naturally
View User's Profile View All Posts By User U2U Member This User Has MSN Messenger
Padstar

posted on 9/11/12 at 10:04 AM Reply With Quote
Jig is wood so not an option. I was thinking of heating up the back of the bent areas and then letting them cool. Would this pull it out?
View User's Profile View All Posts By User U2U Member
Davey D

posted on 9/11/12 at 10:10 AM Reply With Quote
quote:
Originally posted by Padstar
Jig is wood so not an option. I was thinking of heating up the back of the bent areas and then letting them cool. Would this pull it out?


It might pull it back a little if you warm it in the right places out of the jig. Obviously you have some cross bracing around the chassis, so it just working out which braces will be holding the tension, and warming up the areas in the right order to help the steel move as it needs

View User's Profile View All Posts By User U2U Member This User Has MSN Messenger
roadrunner

posted on 9/11/12 at 10:20 AM Reply With Quote
Would putting some more triangulation in the frame sort it out.

Brad.

View User's Profile View All Posts By User U2U Member
Padstar

posted on 9/11/12 at 12:21 PM Reply With Quote
With it just being the lower rails I am hoping a bit of heat and/or gentle persuation will straighten it out. From then on the welds are far smaller and so I should be fine. All of the brace sections will then also be installed so it should all hold together as planned. Just wanted a level base to work from.
View User's Profile View All Posts By User U2U Member
Chippy

posted on 9/11/12 at 02:02 PM Reply With Quote
Shouldnt be too much of a problem, just clamp the frame to the jig so that it is held flat, and so it cannot move. Then build up the remainder of the chassis, just tacking the sections in place. When you come to doing the final welding make sure that you do a little on each side at a time, so that you dont do the same thing again. If done in this manner you should end up with a nice straight frame. HTH Ray





To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy

View User's Profile E-Mail User View All Posts By User U2U Member
Padstar

posted on 9/11/12 at 10:15 PM Reply With Quote
To what extent should I tac the chasis together? Should I not be welding each section as it comes?

Had assumed eAch drawing got welded as its own little masterpiece?

View User's Profile View All Posts By User U2U Member
Confused but excited.

posted on 9/11/12 at 10:30 PM Reply With Quote
The chassis should be tacked together first as chippy said, so that it forms a rigid structure, then weld one joint at a time, moving diagonally around the chassis. This will minimise distortion. Good idea is to mark the joints as you weld them, to make it easier to spot any you may have missed.





Tell them about the bent treacle edges!

View User's Profile View All Posts By User U2U Member
Chippy

posted on 9/11/12 at 10:46 PM Reply With Quote
Yes exactly as stated above, when I built mine I tacked the whole thing with just a blob of weld to hold it all together. Then get your tape measure out and check the whole thing is nice and straight and square, if not this gives you the chance to put it right. Only then as said weld one join at a time alternating across the frame to minimise distortion, and mark with some chalk each one you have done so that you dont miss any, very easy to do. HTH Ray





To make a car go faster, just add lightness. Colin Chapman - OR - fit a bigger engine. Chippy

View User's Profile E-Mail User View All Posts By User U2U Member
Padstar

posted on 10/11/12 at 08:48 PM Reply With Quote
All good. Heated up the area with most deflection and then gave it a little helping hand. There is now a max of 1mm deflection to one area which i believe will fall out as the rest is fabricated. For the rest i will tac untill complete then weld up as suggested.
View User's Profile View All Posts By User U2U Member

New Topic New Reply


go to top






Website design and SEO by Studio Montage

All content 2001-16 LocostBuilders. Reproduction prohibited
Opinions expressed in public posts are those of the author and do not necessarily represent
the views of other users or any member of the LocostBuilders team.
Running XMB 1.8 Partagium [ 2002 XMB Group] on Apache under CentOS Linux
Founded, built and operated by ChrisW.