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Can I ask some questions?

Discussion in 'HA/GR' started by iagsxr, Oct 4, 2008.

  1. iagsxr
    Joined: Aug 26, 2008
    Posts: 159

    iagsxr
    Member

    Hi all, been lurking awhile just have some questions...

    Frame rails; Seems like 2x3 .120 wall is pretty standard. I get that the big size is part of the rules. Just wondering if they really need to be that thick. It's my understanding that NHRA doesn't care what the chassis is ahead of the footbox. If you built the motor mounts to use the engine as a stressed member the unsupported span of the chassis would be fairly short, so .095 or .083'd work?

    What's NHRA say about intermingling moly and mild steel? For instance mild steel frame rails w/a moly cage.

    Front axle; It surprises me the traction problems some of these cars seem to have even on small tires. Seems to me with no rear suspension the only weight transfer comes from the droop of the front axle. Is there anything that can be done to gain more upward travel at the front or is this even the issue?

    Does the relationship of front and rear track widths have any bearing on anything?

    That's all I can think of for now. Thanks in advance.
     
  2. 64 DODGE 440
    Joined: Sep 2, 2006
    Posts: 4,317

    64 DODGE 440
    ALLIANCE MEMBER
    from so cal

    First off.......though the 2X3 .120 wall seems common, you have other options. We are using Model T ford rails as our basis for the chassis and they are quite light. As for mixing moly and mild steel, it can be done as it is on some aircraft, but what the N(o) H(ot) R(ods) A(llowed) may have to say I really don't know. Best way to cross that bridge is buy one of their rule books. (Personal opinions may vary, but it seems that most of the HA/GR builders don't really tend to feel good about their "support" of the little guys).

    Second.......weight transfer can be achieved through many ways, and suspension movement is only one way of accomplishing the goal, for examples go back to the AA/FA class in '60s and look at their work for examples of different ways to get the job done.

    Third.......as for the relationship between front and rear track width, some opinions seem to feel that if the rear is wider than the front some directional stability is lost, though looking at many of the early gassers and first generation altered wheelbase (A/FX0 "FUNNY cars", it doesn't seem to have been a severe problem.

    Please take this with a grain of salt as I will admit that I don't have a degree in engineering or any advanced schooling other that a bunch of back yard garage building and playing with cars from the early '60s to now. It's all just my personal observations and feelings upon which our build is being done and the attitude that hot rodding ain't rocket science and ya can still have fun home building and engineering a drag car.

    Warning!! If you hang around here very long you may be infected with the urge to build on of these cars and your life will be changed forever.:D

    Oh Yes.......You are welcome and keep askin' questions, there are a lot of intelligent people here to help. (Wish I was one of them).
     
  3. for more frame rail material options, consider 1.5"x3"x.120" it's common on t-buckets. Also, 3"round x.120" there were alot of large dia. round tube chassis cars in those early days.
     
  4. Jim Marlett
    Joined: Aug 12, 2003
    Posts: 867

    Jim Marlett
    Member

    According to race car builder Rob Holzman, mixing a chromoly cage with a mild steel frame is done with some regularity and as long as the specifications for the materials being used are adhered to, NHRA doesn't care.
     

  5. vectorsolid
    Joined: Apr 28, 2008
    Posts: 498

    vectorsolid
    Member
    from Montana

    I believe the 2 can be intermingled, but certain rules must be followed on how they are connected. I'm perfectly happy to be wrong, just point me down a better path if I am.

    My understanding of it is that anything that touches Cro-moly should be Tig'd if it's a major piece of the cage.

    Cro-moly to cro-moly =TIG
    Cro-moly to mild steel = Tig
    mild steel to mild steel = Mig or tig.
    Small mild steel bracket to cro-moly cage = Mig or tig. (As an example the window net mount to your Cro-moly cage.)

    As I understand it if you're going to use the thinner wall cro-moly then the joint has to be TIG'd.
     
  6. Correct......although your spelling isn't;):D

    Cheers,

    Drewfus:)
     
  7. vectorsolid
    Joined: Apr 28, 2008
    Posts: 498

    vectorsolid
    Member
    from Montana

    Yea, Me grammar am bad. :D
     
  8. iagsxr
    Joined: Aug 26, 2008
    Posts: 159

    iagsxr
    Member

    Thanks for the responses so far

    Moly circle track cars are mig'ed together, which always worried me because no one uses the proper procedure, but I've seen them survive bigger impacts than an HA/GR will ever take. I've talked with my welder supplier. He assures me that with the proper wire, running pure argon and annealling the welds it's perfectly permissable to mig moly. I don't know...

    My main concern is to build a car that can get through tech at any track.

    Looked at a late-40s Chevy 6 today. It would be babbit bearing'd though wouldn't it? Are all the 6s that take the common Chevy bellhousing too new? Better yet if someone would tell me where I can find this information on my own that would be great.
     
  9. ThingyM
    Joined: Sep 4, 2006
    Posts: 812

    ThingyM
    Member

    If you are looking at running a Chev6.. Try for a later version. The babbit bearing/ splash oiling. does not take to racing that well..Try for the year 55-62 motors.. Better oiling (Presure) and inserts on the rods and crank.. PS..My grand daughter runs in the Outlaw carts. They have mig'd moly chassis.. I don't care for it, But they stay together..I prefer TIG...
     
  10. mudflap261
    Joined: Oct 24, 2005
    Posts: 588

    mudflap261
    Member
    from tulsa

    I think useing chromemoly for roll bars is a mistake for this reason, someone will say we have moly roll bars we need moly frames also. I belive 118 wall mildsteel frames /rollbars would be the way to go . If you have a 6 point cage 095 would work for the rollbars.keep it simple and hold the cost down. What say you
     
  11. FiddyFour
    Joined: Dec 31, 2004
    Posts: 9,008

    FiddyFour
    Member

    if you're into keep it simple and costs down... black water pipe works just as well and a whole lot cheaper than moly or DOM for the cage.
     
  12. ThingyM
    Joined: Sep 4, 2006
    Posts: 812

    ThingyM
    Member

    Water pipe is NOT the way to go for roll bars. It does NOT have nearly the strength of STEEL tubing..And Chromoly is deffinatly the way to go if you have the means to weld it(HeliArc) That is why all your Top Fuel and Funny cars are ALL moly cars.. But it costs about 3 times as much as DOM tubing but is aslso 2 1/2 times stronger
     
  13. two guys I know had their chromoly cages snap off in accidents one is still handicapped so stay with mild steel unless you know what you're doing erw or dom.
     
  14. vectorsolid
    Joined: Apr 28, 2008
    Posts: 498

    vectorsolid
    Member
    from Montana

    Break at the weld or in the tubing itself?
     
  15. 64 DODGE 440
    Joined: Sep 2, 2006
    Posts: 4,317

    64 DODGE 440
    ALLIANCE MEMBER
    from so cal

    I have heard that the problem with the chromoly tubing is that it needs to be "normalized" and some suppliers are selling tubing as normalized that really isn't and under severe impact it can fracture. As I understand the story, this was part of the problem in John Force's funny car accident.

    Mild steel may be slightly heavier than using thinner chromoly but does a good job and will generally bend rather than break, absorbing energy in the process.
     
  16. if chromoly welds are too hot or cool too fast it hardens like the end of a chisel and shatters on impact so all welds should be heat treated or normalized yes suppliers sell 4130N but you can use thinner tubing and it retains it memory (spring back to original shape) better than mild steel.
     
  17. 64 DODGE 440
    Joined: Sep 2, 2006
    Posts: 4,317

    64 DODGE 440
    ALLIANCE MEMBER
    from so cal

    True, but how many homebuilders have the capability to heat treat or normalize properly.

    The KISS theory goes a long way towards making a safer car. In "the spirit of the bug" concept we should try and use techniques that allow for that.
     
  18. vectorsolid
    Joined: Apr 28, 2008
    Posts: 498

    vectorsolid
    Member
    from Montana

    Who at the track is looking at your cage and asking, has this joint been "normalized"?
     
  19. Old6rodder
    Joined: Jun 20, 2006
    Posts: 2,529

    Old6rodder
    ALLIANCE MEMBER
    from SoCal
    1. HA/GR owners group

    True enough, and it's only your butt on the line.

    It is however, their insurance lawyers who'll be getting their medical payouts money back from you personally when their inspection credits your injuries to your ignoring the rules. :D
     
  20. vectorsolid
    Joined: Apr 28, 2008
    Posts: 498

    vectorsolid
    Member
    from Montana

    Never seen how the joint is handled as part of the rules to welding a cage. never been asked about it at the track. Maybe it should be asked.. I don't claim to know. :eek:
     
  21. they cannot tell unless part of the chassis cut away and put in a press to see when it will collapse, the frame will develop stress cracks but it is your ass on the line.
     
  22. vectorsolid
    Joined: Apr 28, 2008
    Posts: 498

    vectorsolid
    Member
    from Montana

    Maybe I don't get out much, I've never heard of a major frame shop that advertises that they do that. Doesn't mean it's not a good idea.

    Mind you, the whole cage debate for the HA/GR cars is that a few builders aren't willing to put in more bars for safety, so going the extra effort on the joints on a cage that doesn't meet spec seems kinda pointless. :eek:

    I don't want to build to meet safety requirements, oh yea, let's anneal these joints. Or whatever it is that you do to them. :) I suspect if a person was truly worried about safety (relative to an HA/GR car) they would build and work around the NHRA safety rule. As you mentioned, it is your ass on the line. :)
     
  23. 64 DODGE 440
    Joined: Sep 2, 2006
    Posts: 4,317

    64 DODGE 440
    ALLIANCE MEMBER
    from so cal

    It's not a case of not wanting to build a safe car, it's using materials that are easy to work with in a backyard build environment to build the car, rather than using stuff that the average builder can't be sure about.

    A safe car could be built using 4130 and an Oxy-Acetylene torch in skilled hands, (that's how many aircraft structures were made in the past and are still made today), but that doesn't mean that tech would approve it.
     
  24. iagsxr
    Joined: Aug 26, 2008
    Posts: 159

    iagsxr
    Member

    Found out that the engine I was looking at is actually a 235 out of a 1960 big truck. Not stuck, ran when pulled, missing starter, carb. Has bellhousing, clutch, clutch slave. What's it worth?

    The transmission that I believe came off this motor looks like it has the same input shaft as a Saginaw 3-speed, but the mounting pattern looks a little different. The engine's on a stand so I couldn't really look at the bellhousing. Could anyone shed some light on the feasibility of mating up a later model trans to this engine?

    Is this a good engine choice?
     
  25. ThingyM
    Joined: Sep 4, 2006
    Posts: 812

    ThingyM
    Member

    Oh come on guys,,, Do you think that ALL the T/F and F/C guys would waste all the time and money on Chromolly if it wasn't the safeist way to go..You didn't see Forces car shatter like glass and fall apart. True, It broke in half, But under those circomstances so would any thing else
     
  26. vectorsolid
    Joined: Apr 28, 2008
    Posts: 498

    vectorsolid
    Member
    from Montana

    monster trucks are a mixture of moly and mild steel. Can you think of any racing vehicle that takes a bigger, and more intentional, beating?

    If you can TIG, moly it up! :)

    And if we're worried about the "backyard environment" of building, where's your stick welder? A welder is something you're gonna own for a long damn time. It's okay to buy one. :)
     
  27. "backyard environment" the two cages I referred to were "PRO" built and I've seen some nice work come out of backyard, it all depends on how qualified you are.
     
  28. 64 DODGE 440
    Joined: Sep 2, 2006
    Posts: 4,317

    64 DODGE 440
    ALLIANCE MEMBER
    from so cal

    Case in point.......if you look at where it broke, that shouldn't have happened. It didn't break on impact, it broke while running down the track.

    The main reason they go with chromoly is the lighter weight they can get because they can use thinner tubing.
     
  29. buffaloracer
    Joined: Aug 22, 2004
    Posts: 806

    buffaloracer
    Member
    from kansas

    vectorsolid,
    Chrome-moly is stronger than mild steel so thinner tubing may be used. That is why the pros use it. Like a grade 8 bolt it tends to sheer under pressure instead of bending like a grade 5 will do. A pro chassis is no longer built in the backyard and must meet all of NHRA's specs. This includes normalizing all welds.
    Pete
     

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