lowgman
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| posted on 26/6/06 at 09:07 AM |
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Just started my build.....
Hello all,
Just started my build on my standard book chassis, and I have a few questions.
[1] I noticed that the top rail J1/J2 doesn't really fit up to the upright H bars well. The FU1/FU2 bars seem like they are totally off.
I'm pretty sure all tubes and cuts are within +/- 1mm tolerance. Is this common? Can I just make sure the j1/j2 bars are in the right place and
cut up new H and FU bars to fit ?
[2] My welding skills are not up to snuff yet, but getting there  I've checked to make sure that I am getting good penetration, but I did blow
quite a few holes. The worse being the one pictured below:
What is the best way to go about filling the gap? Weld along both sides until they are close enough to lay a bead in the middle?
[3] Sometimes when I finish a weld, theres a crater in the middle of the weld where I stop the arc. What causes this and if I grind down a hair, the
weld looks good. Should I be worried about this?
Thanks in advance!
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nitram38
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| posted on 26/6/06 at 10:14 AM |
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Practise!!!!!!!!
When you weld, always weld from the thicker material to the thinner stuff. So start your weld on the angled part of the box and sort of lean the weld
onto the weaker edge of joining flat.
What is happening is the material is burning back faster than you can feed the new metal into replace it.
Try lowering your current a fraction, but not too low that you do not get penetration (ooo er missis!)
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James
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| posted on 26/6/06 at 10:46 AM |
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quote:
Originally posted by lowgman
Hello all,
Just started my build on my standard book chassis, and I have a few questions.
[1] I noticed that the top rail J1/J2 doesn't really fit up to the upright H bars well. The FU1/FU2 bars seem like they are totally off.
I'm pretty sure all tubes and cuts are within +/- 1mm tolerance. Is this common? Can I just make sure the j1/j2 bars are in the right place and
cut up new H and FU bars to fit ?
Hi Lowg,
This is the hardest (and most important to get right) area of the chassis and a such this has been asked many times before.
Firstly, are you using the Mcsorley plans? These are a Locost chassis with The Book mistakes taken out!
Secondly, yes, make sure your 'J' rails are 100% in the correct place first.
I don't understand your problem with the 'H' rails.... are you sure they're 100% vertical in all planes?
Thirdly, Fu1/2..... hold on! Wait a bit for these. Make sure you've got your chassis brackets and wishbones.
Remember the book is wrong in the top wishbone dimension... it should have the BJ centre 22mm off the centreline not 11mm.
Then, make a jig like the one in my photo archive. Assemble the wishbones, bushes, bolts, wishbone brackets onto the jig... you can't fail to
get FU1/2 in the right place then.
Hope that helps,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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andyharding
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| posted on 26/6/06 at 01:40 PM |
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Your gaps will be due to the mistakes in the book. Use common sense to check things and adjust accordingly. Also, as said there are plans you can
download that have all (most?) of the mistakes taken out.
If you blow a big hole in a critical bit cutting out and replacing the tube would be best otherwise as you say build the weld up to cover it then
grind back.
Are you a Mac user or a retard?
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James
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| posted on 26/6/06 at 02:01 PM |
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Oh, and I think you've got you 'L' section verticals on the piss.
The outer face of the tube needs to run parallel to the centreline of the car so that the wishbone bracket sits straight.
But it may be you're ok and I'm picturing it wrong.
HTH,
James
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"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
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lowgman
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| posted on 26/6/06 at 04:35 PM |
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Thanks for the great replies!
The funny thing is, I was trying to follow the McSorley plans  I guess I made a few mistakes along the way.
I might have exaggerated a bit on the "totally off thing", unfortunately I am about 45 minutes drive away from my chassis (and I only have
weekends to work on it). Here's a MS paint drawing of what is off:
Should I make a slight bend in the J tube OR should I just cut the spot welds off the H bar and reposition?
Another couple questions:
Which bars are most critical in a locost frame? Would they be any rails that the suspension brackets are welded on?
How much can I be off on the frame in the end? I did a search and I found that 5mm is not too bad?
Thanks again!
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leto
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| posted on 26/6/06 at 05:40 PM |
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I second everything James say, wait with the FUs, if you place them after the book or McSorley's plans the top brackets will misalign about
5mm.
I suggest you cut out the H and redo it or you will be sorry when you try to skin the car. The outside of the foremost H should be in line with J.
The only thing that is really critical is that the suspension bracket line up in the end. That is LA, LB, FU and M must be right. Getting the other
stuff right will save you trouble later but it's not crucial.
Just like James I'm worried about the way your LB looks to be lined up.
[Edited on 06-6-26 by leto]
[Edited on 06-6-26 by leto]
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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lowgman
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| posted on 26/6/06 at 08:29 PM |
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I built the front end on a plywood jig I made, the tubes should be parallel, but the cuts aren't Maybe that's what is giving the
illusion of LB being not parallel to the centerline.
I will make sure that those LA,LB,FU,M are in the right places. More pics later to come 
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John Bonnett
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| posted on 27/6/06 at 08:25 AM |
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Just started my build
Hi, In the particular joint shown in the photograph, you are welding the edge of one tube to the side of another. You will need to put a lot more heat
into the tube that is side-on compared with the end of the other one. When you weld, you must put in sufficient heat to melt both pieces. Try to bias
your torch towards the piece that needs the most heat. It is the same situation when you are welding two pieces of dissimilar thickness. Also try to
cut your joints accurately so that they fit without large gaps. Large gaps mean more filler, more heat and critically, more distortion.
I hope this helps.
Cheers
John
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Nisseven
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| posted on 27/6/06 at 10:29 AM |
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Just to add to the welding question and to do so I will ask a question. Can you see properly? Many people make the mistake of thinking that just
because you are using such a dark lens that it does not have to be clean it does. With a hole as big as that you should have seen it happening and
stopped much sooner. You might need a lighter lens as well. welding with this thin stuff means you don't need such a big fire and as such it is
not as bright. Shade 9-10 should be OK.
It's not a technique that I favour but for filling gaps you can use the stack of pennies one where you weld in little short bursts. To aviod the
pool at the end pause a little, release the trigger without removing the gun completely so that the cooling weld still has a little gas. Hope that
helps.
Bruce
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John Bonnett
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| posted on 27/6/06 at 10:42 AM |
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Good point Paul. Seeing is fundamental and a clean lens is essential. It is a good idea to change the clear outer glass rather than try to clean off
the splatter.
Even if you don't need glasses, I have come across people who use the cheap Boots magnifying glasses when welding. Just have to find what works
for you. With welding it's practice practice and more practice.
John
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lowgman
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| posted on 27/6/06 at 04:36 PM |
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quote:
Originally posted by Nisseven
Just to add to the welding question and to do so I will ask a question. Can you see properly? Many people make the mistake of thinking that just
because you are using such a dark lens that it does not have to be clean it does. With a hole as big as that you should have seen it happening and
stopped much sooner. You might need a lighter lens as well. welding with this thin stuff means you don't need such a big fire and as such it is
not as bright. Shade 9-10 should be OK.
It's not a technique that I favour but for filling gaps you can use the stack of pennies one where you weld in little short bursts. To aviod the
pool at the end pause a little, release the trigger without removing the gun completely so that the cooling weld still has a little gas. Hope that
helps.
Bruce
Thanks Bruce, I have one of those auto darkening helmets, but I might have set it too dark. However, when that hole was made, I think I lingered too
long on the thinner side of the weld and watched the blob drop into the tubing
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Nisseven
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| posted on 29/6/06 at 12:00 PM |
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The same applies to the auto tint ones, make sure you have a new lens cover especially as you are just learning.
Also I recomend that if you have a friend who is an experienced welder get him to give you some hands on tuition. You will be amazed at how easy and
better your welds will be with a few simple tips.
Bruce
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John Bonnett
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| posted on 30/6/06 at 04:19 PM |
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I absolutely agree. It really is a good idea to have a bit of specialist help to get you started.
I took a welding course at our local college and the benefits are immeasurable. I started with gas welding mild steel and then onto aluminium. At the
beginning, I thought I would never master aluminium but with some good help from the tutor I now find it not too difficult. The same applied to TIG
which I took after gas. You need to have someone who can help you when things go wrong. It's great when the penny drops and you look at the weld
and think, that's pretty good and I did it!
John
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