Dirtbox Venom mini-buggy upgrade/rebuild!

[mysteryboy28]

swingarm, unless people are willing to pay significantly more. there's just so much more work involved in fabricating IRS than there is fabricating swingarms.

meanwhile, stopped at harbor freight to pick up a new regulator, and saw they had this bad boy on sale for $30, down from $50. knock off another 20%, and it's half off!

put the cart together, dropped the welder in, hooked up the regulator - and i didn't have enough gas in the tank to register on the regulator. doh! oh well. picking up a 62 kb tank today (i currently have a 20 lb tank) for a $65 upgrade fee, plus $25 for gas. it costs $17 to refill a 20 lb tank, and only $25 to refill a 60 lb tank. crazy, and totally worth paying to upgrade the tank.

 

[DaiSan76]

You'll be so much happier with the 60. I use a 125, and I only fill it twice a year.

 

[mysteryboy28]

holy crap batman! going from flux-core to MIG is like night and day! i now dub flux-core "flux-crap".

tested the thing out on a nice piece of hardened 3/16" steel plate (harder than your average mild steel). the flux core could barely adhere to it, and the MIG gobbled it up for breakfast.

the weld at the top was without any gas. it seemed to still penetrate well, but wasn't as smooth as the welds with gas (75% argon, 25% Co2). so at least i know if i run out of gas i can still finish up a job i'm in the middle of.

check out the new tank! they ended up charging me $20 more than they quoted on the phone ($110 instead of $90), and said future exchanges will be $32 out the door for 60 lbs of gas, instead of $25. stupid extra charges. blah.

 

[DaiSan76]

I wouldn't weld without shielding gas if I were you. It's there to protect the weld from contamination. You can end up with subsurface porosity that will make the weld weak and brittle.

 

[exenos]

I've got to agree with that. Risk your own life not your customers.

 

[mysteryboy28]

thanks guys. the guy i bought the welder from said he welded without gas all the time. he didn't seem like the sharpest tool in the shed.

been doing a bit of reading and watching youtube videos about mig welding. my example alone shows how lack of gas makes for a bumpy porous weld. i can imagine all the little bubbles inside that weld. the other welds with gas were much smoother looking, and i only had the gas set to about 5 cfh.

according to the what i've read, i should set it around 20 cfh. apparently a common phrase for setting the guages is "20 and 20". any pointers/suggestions on that? i don't want to waste gas, but i want good quality welds. what are other people setting their cfh to (before pulling the trigger)? i found a cool thing on the internet called a gas flow tester that you slip onto the end of the welder nozzle, and when you pull the trigger a little ball floats up and shows you your actual gas flow pressure. they aren't cheap though, about $30 after shipping.

 

[DaiSan76]

This should help.

 

[mysteryboy28]

that info is all over the web. what i CAN'T find is reference to whether that's what the cfh should be DURING trigger pulling, or BEFORE. do i dial in the 20 cfh, and forget about it? or do i try to maintain 20 cfh while welding (with trigger pulled)? i set mine to 5 cfh before welding for those test welds and they looked pretty darn nice i think. but i'd like to do it the RIGHT way - but without wasting gas.

so how about some examples of what you guys are setting your cfh to? how do you set it - before welding or during? are you finding that the gas seems to last awhile. or are you going through tanks like there's no tomorrow?

 

[DaiSan76]

That is during operation. Once you have it set, it won't change. Just pull the trigger and dial it in, shouldn't take more than 5-10 seconds. You can turn your wire feed down all the way, or just release the tensioner before you do it.
This semester At school I am running 30 cfh doing FCAW-G, at home I run 20 cfh on my TIG machine, and get about 12.5 hours of welding time out of my 125 bottles.

 

[r97]

For mild steel, I usually set my flow rate to somewhere between 10 and 15 cfh. Other materials may require a different flow rate. Working in my garage where the wind can't get me, this rate does a good job keeping the weld shielded. As you have found out, setting the flow rate too low can give you porous, weak welds. What you may not have known is that setting the flow rate too high can create turbulence, resulting in poor quality welds, as well as wasting gas. Wind can also blow the gas away, so in some situations you may need to increase the flow. Of course, if there is too much wind the gas will just get blown away, even if you increase the flow. At that time, it would be best to setup a wind deflector, or switch from GMAW to FCAW.

Set your flow rate to be at x cfh during welding. The rate that you see just after you adjust the valve-without gas flowing through the gun-is not what you want to be at x cfh. To keep from wasting wire while adjusting the gas, simply release the wire drive roll tension arm quick release (if equipped) so no wire is fed. If your machine has this function, you could also switch to spool gun mode. Just remember to switch back to standard gun mode/reapply the quick release onto the tension arm. Please keep in mind that the welding circuit is live whenever the trigger is pulled, even on machines that have a safety relay to cut the circuit when the machine thinks it is not welding.

A few months ago I purchased the largest cylinder my local Airgas could sell me that was in stock, a 60 cf 75% argon/25% carbon dioxide gas cylinder. So far I have constructed a welding table, a bicycle, two tricycles, and a bench grinder stand, I have also done a few other random welds for small repairs. I started with a full tank, and a new 10 pound spool of 0.030" wire, I'm a little past halfway through the tank, and maybe 40% through the spool (I would have to weigh the spool to make sure of that). Even if you do not go through gas quickly, get the largest cylinder you are comfortable having in your garage, carrying, and paying for. As you can see, these places give you a much better rate on each refill if you are filling a larger tank.

EDIT: Looks like I got beat to it! I will partially disagree with DaiSan on one thing though. Although the gas flow shouldn't change, I always give it a check after I turn the machine on. Starting a day off with crappy welds because the gas flow changed is not fun, especially if you can't figure out the problem because you aren't accustomed to checking the flow regularly.

 

[mysteryboy28]

got the exaust done tonight. my new welder wasn't cooperating, the line kept snagging up and not feeding, and i have an evil slow leak coming from the regulator area. so i went back to the trusty flux-crap welder for the evening.

it's not pretty, but there's no hard 90 degree corners for the exaust to curve around. i only had to remove a reasonably small section of the exaust to make it work.

 

[greaser]

Very nice it looks like it fits well.

 

[exenos]

Can I scream now?

You might as well ditch that expansion chamber and just run a straight pipe because what you just did will cause the mag cylinder to run best at a higher rpm while the pto cylinder will run best at a lower rpm and the whole design of the pipe is more or less tossed out the window by that section of pipe you cut out. Basically the engine will most likely run like crap.

Read up a bit more on expansion chamber design and theory before you go an butcher another pipe. You'll appreciate it, I doubt that that engine will be putting out anything more that 65hp now.

 

[B man]

Can I scream now?

You might as well ditch that expansion chamber and just run a straight pipe because what you just did will cause the mag cylinder to run best at a higher rpm while the pto cylinder will run best at a lower rpm and the whole design of the pipe is more or less tossed out the window by that section of pipe you cut out. Basically the engine will most likely run like crap.

Read up a bit more on expansion chamber design and theory before you go an butcher another pipe. You'll appreciate it, I doubt that that engine will be putting out anything more that 65hp now.

Chill man.lol yeah its important, but it'll run fine. pesonally i think sleds engines are crap on a buggy anyways, Rev to high imo.

 

[exenos]

If he just shortened the pipe I'd agree that it would run fine, just not at peak power, but it's the uneven y pipe that's got me really worried. Some where around 7.5k one cylinder will be running lean and the other will be rich, that'll flip flop at a higher(?) rpm. The effect will be something like running on cylinder .040 over, not nice to the crank.

 

[mysteryboy28]

the pipe had to be shortened. the manifold had to be redirected. i'm sure an exaust specialist could whip up something more efficient, and that's an upgrade greaser can get down the road. i hear that the 500cc ski-doo motors can be piped/modded to get over 100hp... at which time he'll want to upgrade the drivetrain to handle the extra horses (splined drive shafts, better CV axles, etc.).

obviously if it runs like crap then i will do something about it. but even 65hp is still pretty dang good! the 56hp buggies i've built had tons of power, and were a total blast to drive.

 

[mysteryboy28]

took exenos's suggestion and did some reading on expansion chambers and exaust design (i had to learn something? i don't get paid enough for THAT! lol) - and i've concluded that i really should change things up a bit, and balance the manifold ports so that they exaust evenly. the big reason being that part of the way a 2-cycle motor works is by exausting and sucking back in fuel/air mixture for a power boost (along with sound waves from the expansion chamber). with the uneven "Y" that i made, the fuel/air mixture will get sucked back into the cylinders unevenly, causing an imbalance of power per cylinder. i can only imagine what the immediate and long term effects of that would be. even though both cylinders fire at the same time - as exenos said, it'll put stress on the crank, and the cylinders will have different peak power bands.

so my goal is to make a nice evenly exausting manifold, with enough tube coming from the motor for the fuel/air mixture to be able to do it's business, and then it can curve out the side to the expansion chamber/muffler.

how's that sound exenos? it'd be cool based on my pictures and the limited room i have that you might be able to sketch me up an idea or 2 that you have.

 

[jamyers]

Is there not enough room for a large-diameter 90?
Aren't 2-strokes are more sensitive to volume than corners?

 

[mysteryboy28]

Is there not enough room for a large-diameter 90?
Aren't 2-strokes are more sensitive to volume than corners?

yeah exenos... are they? is there? lol.

in the voice of dr. mccoy from star trek: "dammit jim, i'm a fabricator, not a 2-stroke exaust expert!"

 

[exenos]

in the voice of dr. mccoy from star trek: "dammit jim, i'm a fabricator, not a 2-stroke exaust expert!"

And neither am I. I know the basics and bit more, nothing advanced. (Disclaimer )

Having said that, two strokes are not affected by the volume of the expansion chamber. Its the factors that affect the volume that will affect a two stroke.

If you can keep the length of the pipe (from the start to end of the expansion chamber)the same for each cylinder it would run fine, just not at peak performance. I'll get back to you on the picture but the best course of action right now would be to try to return the y pipe back to stock if possible.



This is a good read that explains the design of a pipe. Starts at page 51 in the book and 62 in the pdf http://www.vintagesleds.com/library/manuals/misc/Two-stroke Tuner's Handbook.pdf