Chassis welding

[croweater]

Hi all,

I have noted that chassis distortion when welding is a norm, so has anyone tried welding up the frame with for example, 3mm spacers under the centre section , after tack welding, then clamping down and finish welding?

This is a process used in welding light structures and long beam lengths and I was wondering if it was worthy of consideration, before setting up my chassis and perhaps having a reverse bow just like the sydney Harbour Bridge!!

Rgds

Brian

[Talonmotorsport]

If the chassis is welded in the correct squence you don't get a bananna shaped chassis. You need to clamp the base rails down in about 16 places to hold it flat then weld methodicly around the rest of the assembled chassis using the heat of the welds to pull it against its self.

[croweater]

Thanks for that.. it was just a thought that crossed my geriatric brain! Appreciate the info.

Rgds

Brian

[voucht]

Hi,
I haven't fully welded the chassis yet, but I clamped it on my table with small brackets you can find in any construction store, the one with a 10mm hole in the centre, at 30mm above the bottom plate. Then I bought threaded bars M10, and some M10 nuts. I cut the bars in pieces of 35-40mm, and put them through the bracket holes, secuted with nuts, just manually tighten. So, the lower point of the bolt is exactly 25mm above the building board, and this will hold the bottom chassis perfectly flat on the board when I'll weld... or at least it is what I expect. I have to confess that the idea is not mine, I found it on a web site, a guy who did it and was happy with the result. If it can give you inspiration, it is a cheap, easy and efficient way to keep the chassis flat when you weld.
I've tried to attach some pictures, but I don't know if it will work. If not, I'll try another way.
Cheers.
S.
F:\Documents\Locost\Images\1erTubes01.png
F:\Documents\Locost\Images\1erTubes02.png

[voucht]

Well, it looks that I can't attach any picture. Do you know how to do it ? When I click on "insert image", it asks me an URL. I thought the URL of the image in my computer will work, but it does not, it should be only for web site links. If you want to see the 2 pictures, send me a personal message with your email address, and I'll send them by email.
Bye.

[K4KEV]

images have to be fairly small file size before you can insert.... them far better to use a hosting site like photobucket where you can load up large file sizes then just copy the link into your thread;)

[voucht]

1233
1234
YES ! I found how to attach pictures to my post (sorry for the mess, I'm new on the forum).
Bye.

[H-L-Smith]

If the chassis is welded in the correct squence you don't get a bananna shaped chassis. You need to clamp the base rails down in about 16 places to hold it flat then weld methodicly around the rest of the assembled chassis using the heat of the welds to pull it against its self.

Could you please expand on what you mean by "using the heat of the welds to pull it against its self?"

Thanks,

Lonnie

[robo]

An easy way to explain what talon is on about is to imagine building a simple ladder say with 5 rungs in it. If you tacked it all together and it was perfectly square then were to weld all the rungs on one side it would take a bananna type set, then going down the other side would not straighten it. But if you did half of one rung and went to the other side and did half of the opposing side then came back to complete the first half an so on it would minimise the distortion. Likewise on the chassis .

Bob

[H-L-Smith]

An easy way to explain what talon is on about is to imagine building a simple ladder say with 5 rungs in it. If you tacked it all together and it was perfectly square then were to weld all the rungs on one side it would take a bananna type set, then going down the other side would not straighten it. But if you did half of one rung and went to the other side and did half of the opposing side then came back to complete the first half an so on it would minimise the distortion. Likewise on the chassis .

Bob

Thank you, Bob.

I see what you mean about doing too much along one side (chassis rail) and switching off as you go. How about the 3-dimensional aspect?

For example, would an expansion of that technique be doing a joint on a lower rail on one side, switching to the analogous joint on the opposite side lower rail then going back to the first side, but now doing a joint on the top rail in close proximity to the very first one you did?

I'm trying to get as smart as I can before I weld up the chassis. It would be a shame spending all this time trying to stay withing one millimeter on measurements then see the result twist by 5mm due to a poor welding sequence.

[H-L-Smith]

1233
1234
YES ! I found how to attach pictures to my post (sorry for the mess, I'm new on the forum).
Bye.

God, the layout on your build table is so neat! Did you do that on a plotter and then glue it on the top surface? It looks too legible to be done by hand.

In either case, congratulations on some very nice work.

[CTWV50]

Thank you, Bob.

I see what you mean about doing too much along one side (chassis rail) and switching off as you go. How about the 3-dimensional aspect?

For example, would an expansion of that technique be doing a joint on a lower rail on one side, switching to the analogous joint on the opposite side lower rail then going back to the first side, but now doing a joint on the top rail in close proximity to the very first one you did?

I'm trying to get as smart as I can before I weld up the chassis. It would be a shame spending all this time trying to stay withing one millimeter on measurements then see the result twist by 5mm due to a poor welding sequence.

If you do find you get distortion and the back or front lifts substantially you can simply grind back the weld on the high side, grind a groove over the old weld and reweld it, 90% of the time this will pull it back into shape. I used this method to fully weld the bottom rails before I started with the uprights and the top rails, I've just finished stage two of the chassis and it's sitting flat.

[voucht]

God, the layout on your build table is so neat! Did you do that on a plotter and then glue it on the top surface? It looks too legible to be done by hand.

In either case, congratulations on some very nice work.

Thank you very much for the compliments mate !
Yes, I drew the base frame map of the chassis on a 2D vectorial drawing software, and then I made it print by a map printer company (the guys printing maps for architects or designers).
Then I pined the map on my table, with the centre line as the main reference. I was trusting my skills with the computer much more than my skills at drawing on the table with a pencil and a square ! And I have to confess that I don't regret it at all : the map was spot on, and the tubes just fitted perfectly. For the price (printing the map was about 20 euros), it was actually worth to do it.
Of course, sometimes when you tack, the paper is burning a little, and you have to be careful and not let it burn too much, but it is not a big deal. Now, after having tacked the complete chassis, yes, the layout looks much worse !
Thanks and good luck to you for the full welding !