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  • Thunder Jet Chassis Warped

    Any suggestions on fixing this Thunder Jet Chassis? I even used a taller tire on the right front still won't touch the track car runs really well but does do a little bouncing in the front might be easier to just find another chassis?
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    Jeff Fitzpatrick
    Troy, New York

  • #2
    Hello, Jeff. Glad to see you're still having FUN with the HO stuff!
    There is a precision fixture used by the FRAY and other HO racing organizations that secures the chassis into the fixture with two drill rods through the axle holes. Then the chassis is boiled and cooled, supposedly correcting any twist you may have. It is intended for original Aurora Thunderjet 500 chassis, I don't know what would happen if you boil a Johnny Lightning or Auto World Thunderjet chassis! I've never used one of these fixtures, so I'm not sure of the exact procedure . I believe they cost upwards of $40. Search around for more info, that's about all I've got off the top of my head. Good luck, stay safe and healthy. Enjoy! -- Ernie

    *** I would suggest you start you search at RT HO, they have many precision tools for the T Jet chassis. Happy hunting. - E

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    • #3
      Seems like all of my JL chassis" are warped

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      • #4
        I understand about warped TJet chassis, having been in TJets for many years, and that chassis straightening jig mentioned above works so well, you'll be tempted to try a few other chassis, just to be sure.

        But, looking at the picture, I think the axle hole may be drilled incorrectly on one side. Is there any other reason to think it is warped? The photo could be fooling me.

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        • #5
          I am seconding the incorrect axle hole location. Both photos seem to show the axle at a slight angle. Only fix for that is tire height.

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          • #6
            Aurora Thunderjet or Johnny Lightning/Auto World Thunderjet? There is a fix for the original Aurora T-Jets included in this article: https://drive.google.com/file/d/1msY...ew?usp=sharing . Warped JL/AW chassis cannot be fixed by the method outlined in the article. The chassis will start to melt and become even more distorted if you try to heat it.

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            • #7
              Holy Cats! There's some good advice from the modern, contemporary HO guy! Be careful! Old farts like me can give dangerous advice, it seems.

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              • #8
                Whats the chassis number? If it's a 4, thats the problem. Notoriously cockeyed. There used to be a list of preferred chassis, and those which were undesirable and the reason. "Fo" is the only one I remember, because it was #1 on the bad juju list.

                A warped chassis presumes that it was once reasonably straight and could possibly be boiled straight, but boiling isnt intended to correct the kind of whacka doodle you've shown. Plastic memory is such that it will always want to be a straight chassis with misdrilled holes.

                Some chassis just are what they are. The quick fix is to flute-ream the top out of low hole until the chassis settles somewhere near level. It'll take a few strokes . Stay patient, take your time, and concentrate on staying square. The idea is to only remove material between 9 and 3 o'clock as you move up to 12. With the chassis load above, axle will naturally saddle into the top of the bore and ride along peaceably for the most part. Once you get it close, then you'll be able to grind a tire to fit, if you still need to make up a smidge. I think you'll be surprised to see what you can actually get away with!

                Hint: I like to use a pocket mirror when I'm trying to get all the corners to touch. Try to slide a feeler gauge under the wheel(s) in question.

                Good luck,

                Bill

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                • #9
                  Originally posted by Model Murdering View Post
                  Whats the chassis number? If it's a 4, thats the problem. Notoriously cockeyed. There used to be a list of preferred chassis, and those which were undesirable and the reason. "Fo" is the only one I remember, because it was #1 on the bad juju list.

                  A warped chassis presumes that it was once reasonably straight and could possibly be boiled straight, but boiling isnt intended to correct the kind of whacka doodle you've shown. Plastic memory is such that it will always want to be a straight chassis with misdrilled holes.

                  Some chassis just are what they are. The quick fix is to flute-ream the top out of low hole until the chassis settles somewhere near level. It'll take a few strokes . Stay patient, take your time, and concentrate on staying square. The idea is to only remove material between 9 and 3 o'clock as you move up to 12. With the chassis load above, axle will naturally saddle into the top of the bore and ride along peaceably for the most part. Once you get it close, then you'll be able to grind a tire to fit, if you still need to make up a smidge. I think you'll be surprised to see what you can actually get away with!

                  Hint: I like to use a pocket mirror when I'm trying to get all the corners to touch. Try to slide a feeler gauge under the wheel(s) in question.

                  Good luck,

                  Bill
                  The Chassis is indeed a "4" sounds like other than swapping out the chassis itself think I'll try to open the axle hole upward a bit maybe that will be enough to get it running a little smoother even with the crooked front end it still runs comparable lap times with the rest of the Thunder-Jets I'm not sure exactly where i got that chassis from but I'll be sure to put the "4" on the bad list do you know where to find that list? I'd be curious to see what else is on there thanks for the help.. Jeff

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                  Jeff Fitzpatrick
                  Troy, New York

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                  • #10
                    Thanks for all the help on this guys!
                    Jeff Fitzpatrick
                    Troy, New York

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                    • #11
                      The list? Oh boy, it was waaaay back on H0 World or Hobby Talk.

                      Check on that rear axle too, most of the journal is exposed inward, so the outer splines are riding in the chassis. That rim looks kinda close to the frame rail anyway, and might bind under side loading. I'd reset the axle and make sure you have some visual clearance between the wheels and the frame rails.

                      I grind the stock T-jet tires all the time. It's almost mandatory. Especially for the front. Usually it just takes a touch. No fancy Hudy machine needed. An old inline magnet car chassis for a slave/grinder, some 180 or 220 grit paper, and drop through tire gauge or calipers. Well, admittedly I need some 'readers" to see what the heck I'm doing.

                      Does the bounce occur all the time Jeff? I'm always suspicious of after market rims until they are proven to be true. It's a never ending job around here. It sounds kinda persnickety, but the primary handling issues for ALL pancake cars are whacked wheels and tires, and goofed up shoe geometry.

                      Bill

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                      • #12
                        Originally posted by Model Murdering View Post
                        The list? Oh boy, it was waaaay back on H0 World or Hobby Talk.

                        Check on that rear axle too, most of the journal is exposed inward, so the outer splines are riding in the chassis. That rim looks kinda close to the frame rail anyway, and might bind under side loading. I'd reset the axle and make sure you have some visual clearance between the wheels and the frame rails.

                        I grind the stock T-jet tires all the time. It's almost mandatory. Especially for the front. Usually it just takes a touch. No fancy Hudy machine needed. An old inline magnet car chassis for a slave/grinder, some 180 or 220 grit paper, and drop through tire gauge or calipers. Well, admittedly I need some 'readers" to see what the heck I'm doing.

                        Does the bounce occur all the time Jeff? I'm always suspicious of after market rims until they are proven to be true. It's a never ending job around here. It sounds kinda persnickety, but the primary handling issues for ALL pancake cars are whacked wheels and tires, and goofed up shoe geometry.

                        Bill
                        I see what your saying about the rear axle think it's time to remove it for cleaning anyway I'll get that in the right spot is there any video's of the tire sanding love to see that done I have a Tire Razor for the bigger cars never sanded the smaller ones and it doesn't bounce all the time and never on a straight
                        Jeff Fitzpatrick
                        Troy, New York

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                        • #13
                          You don't have to remove the rear axle to get rid of any lint or hair that might have gotten wrapped around the axle. If a wheel is snug up against the chassis you should use something like the blade of an X-acto knife to pry it away from the chassis a little. Hair wrapped around the axle between the chassis and the wheel can be removed by wrapping a couple of turns of string or dental floss around the axle and pulling on one end. You might have to do that several times. Hair caught next to the crown gear can be scraped away.
                          I bought my first Aurora T-Jet when they were first introduced in 1963. I had at least a dozen of those and every one ran perfectly straight out of the box. Some aftermarket wheels are injection molded just like the original Aurora wheels were. A person that I know had reproduction wheels made and the samples that I have examined have been good. Those wheels are sold by JAG Hobbies and other dealers. A fanatic might want to consider using CNC machined aftermarket wheels.

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                          • #14
                            Fitzy,

                            I doesnt really matter who makes it or sells it, it's our job to verify by checking; because the supplier doesnt check them! Here's the no-buck quickee H0 tests, that you can keep in yer back pocket, to help you weed out the culls. The hardest part is coming to grips with condemning parts that look fine statically, but are not fine at speed.

                            1. For rears: Block the chassis up in a hands free fashion, apply minimum power and watch the rim. If you can see the bead ride up and down or wobble side to side, it isnt straight; and no amount of wishful thinking will make it straight.

                            2. For front: Take the guide out and run the fronts across a mirror or a chunk of glass. Grip the car so that your index finger is lightly on the hood. Gently roll the front back and forth across the surface. If the car pulses against the pad of your index finger, or wobbles side to side, something tire or wheel isnt right.

                            3. The spit test: A bit of light oil works too. With the pad of your index finger wetted, ease it under one running rear tire, then the other. A good set will fry the liquid right off, and dry your finger. It should feel smooth and progressive, as the tire finally grabs traction on your finger. Typically a bad wheel-n-tire combination will thrum/vibrate rhythmically against the pad of your index finger.

                            This all presumes that the axle bores are square and running clean, and that the body isnt binding or rubbing a tire.


                            Last edited by Model Murdering; December 2, 2020, 12:07 PM.

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