Spidercarts GrandDaddy Build by extreme0016

[Felineman]

Welcome to the forum & good luck with your build.

Here's a tip (which would've been handy before you started cutting): As opposed to cutting all the pieces to length, simply cut a V into the tube where there's an angle & bend it to shape. This process keeps some of the strength in the material &, therefore, in the finished product.

I have to say as a welder and 13 years auto scrapyard and 12 year machinist YOUR WRONG the weld is the strongest part heat treated and low in carbon.

 

[OzFab]

I have to say as a welder and 13 years auto scrapyard and 12 year machinist YOUR WRONG the weld is the strongest part heat treated and low in carbon.

My wrong what?

Well, after 15 years as a panel beater/fabricator, yes, the weld is the strongest part but, the area directly adjacent to the weld is the weakest so, how can a full weld possibly be stronger than the original steel?

Oh, BTW, we don't straight out say "you're wrong" around here, that just comes across as arrogant & that you know better than everyone else; isn't is funny how YOU are the only one to agrue this point...

 

[Poboy kartman]

Wrong!.....You've seen me post that on occasion. ...I don't say "you're wrong"... it's a subtle difference.....but you're right. ..I do it to emphasize strong opposition to the statement- but not the person....

Sometimes it's just a small little difference in opinion but the difference in clarity in the statement that is the problem. .....

I don't know who is more correct on the strength issue- but "you're wrong" does come off as pompous to me. ....

 

[Poboy kartman]

Sorry for the double post- but I thought about this for a minute and I actually do have an opinion on this:

It took me a minute-but I got to thinking about what I do know about -wood.....and the fallacy/truth regarding glue joints. ...a well made glue joint is stronger than the wood that surrounds it and the wood will give way before the joint......TRUE!!!!!

However- I have had to break stuff apart before and the majority of the time you can get the glue joints to fail with minimal damage to the surrounding wood. Why? Because most glue joints aren't well made...Most are glue starved-and to get a perfect glue joint- it must be clamped.....

So- the same rules apply to welds.....and where do most weld assembled machines break? At the welds?

So I guess you could both be right.....and certainly neither totally wrong. ....

 

[landuse]

The only time I have ever seen a frame break/crack, it has been at the weld joints. NEVER anywhere else. That should tell you something

 

[itsid]

Well from the little I know about welding (close to nothing) and
what I know about physics (fits in a hand)
I tend to say both statements are true somehow.

And here's my explanation for this:

heating steel without proper tempering
makes it very brittle too meaning it breaks before it bends.
[edited.. thanks DaiSan]

The weld joint is different, different material, different material thickness and very different way of bringing metal into a form.
thus chances are that a good weld will be stronger than it's surrounding metal.
(not the original metal though)

But in fact it's not better than a good bend.
Although a bend weakens metal too
-most bends around here are cold pulls so the outer wallthickness will decrease-
the fact that the metal wasn't heated the part kept it's original flexibility.

And flexing is what you need in a unsuspended kart,
that's not an issue of comfort, but of preventing the kart from falling apart.

The times I've seen people breaking welds, the metal will give away before the weld true, but always directly NEXT TO the weld,
and the reason for that is the welding, not the weakness of the material as such.

I guess if you temper your frame after you're done
the weld if filed down to the exact same thickness as your original material will be the weakest spot.
[edt again]
lower on carbon.. perhaps (not necessarily though) but that doesn't help anything after all the heat

Try this at home:
get a welding wire cut it in two, join it with a weld spot, let it sit on your bench to cool
file it down again and try to break it.. (don't cheat )
Now repeat but anneal it first.
See what happens

Feline, allow me to say a few more words...
The first thing I saw one of your posts, you stated that you and your dad with a combined knowledge of 50something years of being a machinist
couldn't figure out a way to stick a 1" axle through a 1.5" hole...
just to find out that the part to do that properly is already available
for at least 20 of said 50 years.

The second time one of your posts sticked to my mind is
when you say a Honda GX (not a clone, but the real deal) is crap.
Which can be considered as blasphemy,
at least it's the most uneducated opinion I've heard in a while

And now your statement again is at least arguable;
as it contradicts nearly everything
bike, kart and car builders do for a lot more than 5 decades.

In the end, I'd say you chose your usertitle wrong...
it should say "Death by misinformation"

'sid

[EDIT]
I edited this post after the clarification from DaiSan below.

 

[DaiSan76]

The only time I have ever seen a frame break/crack, it has been at the weld joints. NEVER anywhere else. That should tell you something

It should tell you that those joints were not welded properly. If you follow proper welding procedures, the joint will be stronger than the base metal. The most common filler metal used in hobby grade machines on mild steel is 70,000 tensile, while the base metal is 58,000. When a weld breaks in the heat affected zone, it means that either too much heat was put into the metal, or the metal was forced to cool too fast.
Sid posted about cooling the metal in oil being a good plan, but that is not accurate for this application. Rapid cooling of metal produces Martensite, which is very hard, but very brittle. For our application, you want slow cooling, or annealing which produces a ductile joint, which will flex or bend rather than break. Maybe when I have more time I'll post some pictures.

EDITED:

This is the best image I could find, and I am too lazy to draw my own and take pictures of it. You'll just have to imagine what those lines would look like if you had undercut, or a great big wad of metal growing out of your nice weld. Any imperfection in the weld makes those stress lines go all sorts of wild, which makes your joint prone to breaking. I've spent the last 2 years doing pretty much nothing but making test plates to bend or break, so I've seen firsthand how crappy welding, slag inclusions, and quenching affect the ductility and strength of your weld.

 

[itsid]

Sid posted about cooling the metal in oil being a good plan, but that is not accurate for this application. Rapid cooling of metal produces Martensite, which is very hard, but very brittle. For our application, you want slow cooling, or annealing which produces a ductile joint, which will flex or bend rather than break. Maybe when I have more time I'll post some pictures.

Hmm *headscratch* you're right..
needs to be tempered (after it has cooled down) to regain flexibility.
I always mix up Austenite and Martensite.
(stalagmite, stalagtite... )
On a side note: could you explain the difference between annealing and tempering?
it's a wire-cable thing in german.. *shrugs*

Anyways, it's still the welding that weakens the material

'sid

 

[DaiSan76]

Annealing is heating the metal to Austentizing temperature, holding it there for a period of time, and then allowing it to air cool. This allows the metal to align so that it is no longer under stress.

Tempering is heating the metal to Austentizing temperature, and then at some point, quenching it in one of many substances, including oil, or brine. The sooner you quench, the more Martensitic (is that actually a word?) the metal will be, which means it will be harder, but will not bend.

If you have a static loaded piece, you want it to be very hard. Like a sprocket, will have continual force pushing towards the center, but if everything is set up right, will not have shifting forces.

The frame, on the other hand, is a dynamically loaded piece and will have constantly shifting loads coming from different directions, requiring a more ductile, elastic metal.

 

[DaiSan76]

Oh, and the reason your weld joints are weaker is not because of the process of welding, it is due to the creation of stress risers.
I'll try to get an illustration posted tonight, but I have class right now.

 

[itsid]

Annealing is heating the metal to Austentizing temperature, holding it there for a period of time, and then allowing it to air cool. This allows the metal to align so that it is no longer under stress.

Tempering is heating the metal to Austentizing temperature, and then at some point, quenching it in one of many substances, including oil, or brine. The sooner you quench, the more Martensitic (is that actually a word?) the metal will be, which means it will be harder, but will not bend.

If you have a static loaded piece, you want it to be very hard. Like a sprocket, will have continual force pushing towards the center, but if everything is set up right, will not have shifting forces.

The frame, on the other hand, is a dynamically loaded piece and will have constantly shifting loads coming from different directions, requiring a more ductile, elastic metal.

Oh I see.. in german both is referred to as "Anlassen" (Tempering)
And the main difference is the temperature
stage 3 (320-520°C) for example means levelling cementite and ferrite softening the metal...
quenching "Abschrecken" or not just adds a coating (or not)


Whereas "Ausheizen" is a way to fix broken atomic structures by heating the metal and cooling it slowly
(copper, silver and brass can also be quenched)
healing the metal (which you would translate to annealing)

But details like these get lost in translation, and I do too

So thanks for explaining.

Just one thing.. I happened to ask wikipedia before you answered...
and I read

Tempering is a heat treatment technique applied to ferrous alloys, such as steel or cast iron, to achieve greater toughness by decreasing the hardness of the alloy. The reduction in hardness is usually accompanied by an increase in ductility, thereby decreasing the brittleness of the metal.

So uhm.. *shrugs* I'm lost...
metallurgy isn't exactly my bright spot

'sid

 

[DaiSan76]

I think of "tempering" as doing anything to steel apart from allowing it to cool in naturally in air. I did a lab last semester where we took 10 samples of aluminum and brought them up to temperature, we then started taking the samples out, and allowing them to cool progressively longer before quenching, and then taking them to the Brinnel or Rockwell machine, (I don't remember which) and testing their hardness. The control sample was fully annealed, or allowed to cool naturally. I'm not a metallurgist myself, and the terminology starts to get out of hand pretty quickly. I could easily be using the word "tempering" completely wrong.

 

[extreme0016]

Okay, so it's as done as it's going to get. I put all the finishing touches up on it over the past few weeks. Lights, flooring, paint touch-up, minor tweaks, and it runs great. I will probably add a better exhaust, intake and a few other engine tweaks to get some more HP, but the core project is wrapped.

I have named it The Black Widow. It has been an awesome project, and now I am deciding on the next project. I am for sure going to build a little SpiderCarts Recluse because I have a ton of friends and neighbors who now after seeing my project want to build one, so that seems like a nice small group project where we can build a half dozen or so of them together. After that, who knows.

Here is a YouTube of the finished product:

https://www.youtube.com/watch?v=YjgIpO7-aQs&feature=youtu.be

 

[desrtrat]

Cool, looks awesome and seems to move out pretty good.

 

[2SlickNick]

Awesome ride!! Looks so full of torque. Great job!