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Learning how to build Lotus Seven replicas...together!
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PostPosted: Sun Jun 03, 2012 5:45 pm 
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Open mouth, insert foot. Isn't that the way of it? I figured it out my own stupid self because "necessity is the mother of invention" and I wanted to put this problem to bed ASAP even though I could let it slide for a while.

First, I moved my welding table so it was situated under a really bright spotlight near the bandsaw and positioned it to illuminate the area to be welded. It is surprisingly hard to see in those narrow spaces when the torch is arcing. I though the really bright, focused spotlight would help and it did.

Second, I clamped the tunnel bottom (the part) vertically off the side of the welding table so the joint to be welded was at the bottom of the Vee and gravity would take molten metal down to it naturally.

Third, I kept the MIG nozzle on this time, but gave the filler wire out about 1/2" of stick out.

Fourth, I made two small beads just above the joint and let them slough off and flow towards the Vee joint. That left a wider gap to fill, but it was more accessible than the original even with the nozzle attached.

Last, I ran a new bead in between the two smaller ones and let the wire and molten go down between them and just kept feeding wire, moving it side to side, and letting it melt until the gap filled up. The result is a sort of "super fillet." It's more filler material and more actual fillet than necessary to join the pieces, but it got the job done. They are definitely stuck together.

I flipped the part 180 degrees and did the two on the other side in the same way. I won't use a narrow angle like that again unless it is an absolute necessity.

So, now on to the next problem.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: Sun Jun 03, 2012 5:47 pm 
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Hi Lonnie..nice people mover..Reds always faster..i always use stick for acute welds,low setting with the right rods..probably because i dont own a mig.. :) My old boss taught me to arc weld on exhaust pipe :shock: so welding thin gauge steel isnt a problem

kiwi Dave

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PostPosted: Sun Jun 03, 2012 6:36 pm 
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laserracer wrote:
Hi Lonnie..nice people mover..Reds always faster..i always use stick for acute welds,low setting with the right rods..probably because i dont own a mig.. :) My old boss taught me to arc weld on exhaust pipe :shock: so welding thin gauge steel isnt a problem

kiwi Dave


Red is always faster, isn't it? The local police here are rumored to agree with that statement.

I've done stick welding. It's the first process I learned in a recent welding class at a local college. Rod selection is everything in stick welding because it give you almost every characteristic: penetration, freeze rate, flux/shield, etc. I was motivated by not wanting to have to figure out which rod type and size to use in the fix of my problem because it's time consuming. That's why I gave MIG another shot, which worked out OK this time.

If I did a lot of these acute angle welds, I would definitely invest the time necessary to use stick welding in this situation.

Thanks for the info.

Regards,

Lonnie

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: Mon Jun 04, 2012 12:18 am 
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Just a thought, but have you considered using a small gusset in your acute corners? It wouldn't need to be big, 1/2" on each edge, but it would allow you to tie the inside edges of your tight corner together in a structural manner.


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PostPosted: Mon Jun 04, 2012 8:52 am 
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esp42089 wrote:
Just a thought, but have you considered using a small gusset in your acute corners? It wouldn't need to be big, 1/2" on each edge, but it would allow you to tie the inside edges of your tight corner together in a structural manner.

I hadn't actually considered that. Do you mean taking the gusset all the way into the apex of the angle or running it shy? I could see where a gusset could be a substitute for welding the join itself if you ran it say 1/4" or more shy of the apex. That would prevent you from having to weld the narrowest part of the joint, which is the real problem. Is that what you mean?

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: Mon Jun 04, 2012 5:08 pm 
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This might be what He meant. This is what I did. I cut small wedge sections of square tubing and filled in the narrow area with them like this.


Attachments:
Tough-MIG-Welds.gif
Tough-MIG-Welds.gif [ 180.51 KiB | Viewed 511 times ]

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PostPosted: Mon Jun 04, 2012 5:47 pm 
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One other alternative is to cut 4 triangles and make shear panels on both sides. It is a bit more welding but the welding is easy access.

Me, I'd just poke the mig nozzle into the narrow angle as far as it will go and start at the far side and work toward outward to me. The MIG nozzle is at a very acute angle relative to the weld line, and your are welding a far distance from the nozzle but it seems to work for me.


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shear panel.jpg
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PostPosted: Mon Jun 04, 2012 9:08 pm 
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you could get a nozzle for the mig and flatten it a bit if you were that worried.

i used to have mig nozzles with bits cut out of the end for doing plug welds so you could apply pressure to the top material to hold it down with the nozzle, and a flat one for doing just what you needed there.

keep the nozzle clean though or it will ground out and the weld won't be where you want it.

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oh to go down to the strip again where the blacktop meets the sky
all i ask is a small block and some fuel to make her fly
with slicks a smokin pushrods pokin next round i'll get a bye

she's up on song the shift was strong in the finals to boot
it's back to the pits and take it to bits and don't forget the shute
the final round was good and sound so come on give me the loot


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PostPosted: Mon Jun 04, 2012 10:43 pm 
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MYTF wrote:
This might be what He meant. This is what I did. I cut small wedge sections of square tubing and filled in the narrow area with them like this.


That is exactly what I meant, thanks for taking the time to mock it up on a photo! It would allow you to strengthen up the inside of the joint considerably, weigh little more than welding the inside seam (if you managed to), and in my eyes still look presentable.


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PostPosted: Mon Jun 04, 2012 10:47 pm 
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I like the wedge approach esp42089/MYTF suggested. That looks strong and pretty do-able.

I think the area in question looks bigger in the photo I posted than it is in real life. I don't think even flattening the nozzle would help much in my case.

When I did lay the two smaller beads above the apex, I could use the extended wire technique. Before that, I tried welding at the apex in the narrow Vee with the extended wire approach Chuck suggested, but it acted like a cutting torch on the far side, melting off the end of a tube. I fixed that pretty easy because it was at the very end and accessible.

If I can, I'll avoid such sharp angles in the future. If I can't, then next time I'll try the "little wedges" approach.

Thanks to all who made suggestions. It's much appreciated.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: Mon Jun 04, 2012 10:56 pm 
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See! Told ya iffen we waited around a minute or two the Smart People would figure it out! :mrgreen: Ain't that a great plan? Works every time! :mrgreen:

:cheers:

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PostPosted: Tue Jun 05, 2012 12:54 pm 
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GonzoRacer wrote:
See! Told ya iffen we waited around a minute or two the Smart People would figure it out! :mrgreen: Ain't that a great plan? Works every time! :mrgreen:

:cheers:

Amen!

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: Thu Jun 07, 2012 7:52 am 
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To weld those acute inside angles you can do as suggested and flatten a nozzle a little and also shorten it. You will still have a longer wire stick out though so to compensate you may need to bump the current a little. It also helps to increase the gas flow. If you start in the middle and weld out then the longest you have to reach is a little over 1/2 an inch. I know that you are welding the wrong way ie. pulling the torch as apposed to pushing it but it is only thin material and you will get away with it. I hope you will forgive me for saying, but some of your welds look a little cold and I would try a little more current with the same wire speed or viciversa a little less wire speed but the same current.
Bruce


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PostPosted: Thu Jun 07, 2012 10:13 am 
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nisseven wrote:
To weld those acute inside angles you can do as suggested and flatten a nozzle a little and also shorten it. You will still have a longer wire stick out though so to compensate you may need to bump the current a little. It also helps to increase the gas flow. If you start in the middle and weld out then the longest you have to reach is a little over 1/2 an inch. I know that you are welding the wrong way ie. pulling the torch as apposed to pushing it but it is only thin material and you will get away with it. I hope you will forgive me for saying, but some of your welds look a little cold and I would try a little more current with the same wire speed or viciversa a little less wire speed but the same current.
Bruce


Thanks for the response, Bruce.

All this welding stuff is more complicated that one first suspects, isn't it? I know my welds on this piece do look a little mounded, but I've done a good amount of testing on scrap pieces of 0.75" x 16 Ga. RHS (as in this part) where I can see the underside of the weld on the tubing scraps. The penetration is just about ideal and I can see the metal just beginning to pucker right at the underside of the join with clear discoloration from the arc heat, so it should have fused together. If I up the current, it starts to sag underneath, which I know isn't good. I don't know why the bead isn't flatter. Too much filler wire maybe? Maybe it's something to do with my personal welding style like moving too slow?

My welder has "auto selections" based on the thickness of the material, but I've found it is too hot for my welding style and I see too much sagging on the underside of the welds consistently.

I do use a push, though. That's how I blasted off the corner of one tube when I was trying long stick-out in the acute weld. The low angle of the filler wire just pushed it right off when it got molten rather than fused to it. From my testing on scrap, I do have a "cheat sheet" of settings for various material types and thicknesses that should give good, strong welds even if they're not too pretty.

It would be great if I had the benefit of years of experience welding before taking the chassis on as a project. In that case, I would be anticipating these issues and solving the problems in real time as they arise, or better yet, avoiding them all together. Unfortunately, that's not the case. Every day is a new adventure! That's what it's great to have a resource like LocostUSA.

I tell you, this experience has amplified my already appreciable respect for people who make things, especially race cars. But, I'm like that musician who wants to go to Carnegie Hall, so for me it's practice, practice, practice. :lol:

Thanks again,

Lonnie

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: Thu Jun 07, 2012 10:42 am 
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The Locost is my first major welding project, so I'm no expert, but I got a lot of help from watching videos. One thing I learned early on is that the technique of working the torch back and forth across the seam, with a slight pause at the end points, really works for me. It makes a solid weld and a nice bead to boot, and that's using the autoset feature. My early beads looked kind of narrow and lumpy.


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