4130 Front engine dragster help needed!

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Building a Front engine "Digger" type dragster. Think Garlits "Swamp Rat" but certed to todays standards. All 4130 MUST be TIG'd by NHRA rules. Using 1 5/8 OD .095 wall moly. How many amps will it take to weld? Good at MIG but new to TIG. Wanting to tack it up by MIG .023 wire Co2 and have it finish TIG'd OR buy a unit and do it myself. Thoughts? Ideas? Looking for an inexpensive TIG with finger tip control and as a bonus I have a master welder to teach me TIG if I ask nicely, or will weld it all up for me. I'd rather learn the process myself. Been studying Millers PDF TIG course. I am taking this seriously. Yes I know the welds must be strong to be safe. I have the SFI books on tubing placement and sizing.My doorslammer Mustang runs 7's at 193 mph in the 1/4 that I built...I don't fool around...MarkHammerhead RacingEdgewater Fl.  www.hammerhead1320.com
Reply:well on amps to use, there is kinda a startin point of 1 amp per .001 wall thickness. So in your case of .095 tubing = 95 amps. Now be VERY careful of pre and post heat usally 4130 less than .120 doesnt require preheat. On choices of welding machines to purchase, remember  you get what you pay for!!!! if you are going to be racing=your going to break things at the track right !!!!! so my suggestion would be a AC/DC inverter for the simple reason you can GTAW (tig) your aluminum aswell.. On what brand, well whats your choice I prefer Lincoln V205T AC/DC or V160T DC . Either one will run off 110/230 single phase. I have a V205T AC/DC and very happy,smooth arc, enough controls for tuning but not to many to be a pain!!!! Good welds and safe weldin= returnin home after a day at the track!!!!!!welding instuctor
Reply:I do mostly auto/race based projects as well so nothing super thick.  Lots of cage/chassis work, and header/exhaust/intercooler/airpipes etc.  I have had good luck with the Thermal Arc 185 machine. It is a AC/DC small inverter machine.  It reasonably priced.  I have been using it for 3 or 4 years without a single issue.  Just a suggestion.95 amps is ballpark like stated above.  I don't like the finger tip control personally even when doing cages in wierd places.  I feel like I have more control with the pedal.  Tacking with the Mig then welding with the Tig is fine.  Just keep the tack welds small and clean and you can burn right over the tops of them while tig welding it all up.  Fit-up is everything when doing cage/chassis work with  the tig so tight joints with no gap will help get you some sound welds.  The better the fit-up the easier it is to weld.Last edited by standfast; 12-01-2009 at 12:08 PM.
Reply:My $.02, if someone brought me a moly cage that they tacked up with a MIG, I'd send it right back out the door.  If you're going to do it properly, you will have to remove every one of those tacks.IMO, you will find 95 amps too much for most of the welds.  Personally, I'd go with a foot pedal control.  I've built quite a few cages, and always found a way to use the foot pedal.  I've often had to hold the torch in ways that a fingertip control wouldn't be accessible or would interfere.  On a digger, you can just flip or move that chassis at will to get at virtually any joint, and if its on a jig, it's up high enough to get at comfortably anyways.Honestly, I wouldn't make a digger my first TIG project, regardless of whether I had practice or not.  Too much to go wrong with tubing that thin and a chassis with as much flex in it as a digger.  Door cars are far, far more forgiving than the rails.
Reply:A year and a half ago I purchased a miller dynasty 200DX for an application like this, it worked out really well. we had it set up with the foot pedal. One nice thing was the small size, the other was the fact it would run on 125v power all day long. we almost never used 220 or 208 v power even though both were available.      It was really easy to set up, and handled chrome molly, aluminum, stainless, titanium and stick welding of fairly thick carbon steel with 1/8 inch rods, with no issues or problems. training was fast, we trained a dozen guys to use it.      The pulse was nice on thin stainless and aluminum. I would train tig welders by starting them up running beads on the edge of 14 gage steel, then doing corner welds on the same material. Technique and control rather than flash and flame.      We set it up in a rolling workbench with a miller 375 plasma, air compressor and a millermatic 180 ( with spool gun) , and a oxyacetylene set. Nice setup. The whole thing would run on a 5kw generator. We paid for the whole setup with scrap sales. -Scrap was high so we cleaned the shop!      One thing we used it for was the SAE minibaja competition. Same frame rules as you are working with.      We purchased a 2nd one for a different lab as well. expensive, but NICE MACHINES!!!!      One nice thing is that nobody will fault you for using it. And in racing you get one chance to win. You would think nothing of a lot of money for car parts, this will save you more than it costs.past work toys; lathes,mills, drills, saws,  robots, lasers ironworker, shears, brake, press, grinders, tensile tester,  torches, tigs, migs, sticks, platten table, positioner,  plasmas , gleeble and spot. Retired June 30, 2009.
Reply:As you know, there are lots of good race car fab shops is Florida.  I do no think there is a chance I would learn to Tig on my race car chassis.  Not with my butt going 200 mph on my practice welds.  You've got 30k in a motor, why not throw a couple extra K in making sure that your cage is safe.Just my .02.Let me know if you need the name of a good chassis shop.What class are you running in? NMCA, NMRA?  10.5?Last edited by jmtebbens; 12-01-2009 at 04:12 PM.
Reply:I definitly agree with most of these people i would not start to learn to tig on a race car body it would be pretty difficult to get a decent weld done for a experienced welder let alot a someone just starting
Reply:I have some very good TIG welders across the streeet from my shop. 20+ years at it. They can weld me up. I am familiar with Suncoast and Coast Chassis also. Just in there today. Pete and Tim are great guys.MarkHammerhead RacingEdgewater Fl.  www.hammerhead1320.com
Reply:I also have a new Lincoln V205-T AC/DC machine, it's a great machine, and would probably weld most of your chassis (except for maybe the thicker stuff like .250 if you have any plans to use it for rear end mounting, etc.).I also agree that learning to weld on a race car chassis may not be the best way to go, but I guess you are the best judge of that.Regards to all.Working on cars and bikes is my hobby, learning to weld the pieces together is my quest.
Reply:BTW, I am also taking classes currently at our local college, I have another class starting in late January, I have had one TIG class stream already (10 weeks, 2 nights a week), and the class in January is also TIG but I will be focusing on 4130 welding (I am already practicing on my TIG).I find that welding 4130 can be tricky (I am currently trying 1.625 tubing with .083 wall, and .090 plate in 1 inch wide strips), too much heat or not enough heat can make a big difference in the quality/safety of the weld.  Not to mention Tungsten type/size, Argon flow rate, rod type/size (I am currently experimenting with ER70S2), speed of welding, how and when you dab the filler rod, etc., etc., etc.After my classes so far, and my practicing, I feel I am far from proficient enough to weld a race car chassis; actually after looking at the pictures that Paul posts (ZTFab) I am not sure if I will ever be truly ready to weld my own chassis.Regards to all.Working on cars and bikes is my hobby, learning to weld the pieces together is my quest.
Reply:Originally Posted by DavidSimI also have a new Lincoln V205-T AC/DC machine, it's a great machine, and would probably weld most of your chassis (except for maybe the thicker stuff like .250 if you have any plans to use it for rear end mounting, etc.).I also agree that learning to weld on a race car chassis may not be the best way to go, but I guess you are the best judge of that.Regards to all.
Reply:>>The invertec 205 can weld 3/8" steel with no problems. Proper bevel and fit up, and mash the pedal to the floor. It gets PLENTY hot with 200 amps for 1/4-3/8 plate<<Thanks for the follow up, it's good to know.Regards to all.Working on cars and bikes is my hobby, learning to weld the pieces together is my quest.