Gunderson Maxi-I Repair

tjdreams Apr 23, 2023

  1. tjdreams

    tjdreams TrainBoard Member

    Earlier this week while moving a set of well cars from my test track to the show box I picked up the 2nd car (the one with out wheels attached) expecting it to lift off the pins but the end care came up with it and before I could react the end car came loose and fell hitting the edge of the test track Base on its way to the floor Breaking the little pin that the car mounts too clean off. Had it been one of the other 2 mid cars with one truck I could have just left that car out but being the end car with booth sets of trucks its needed so it needs to be repaired.
    After taking some measurements and thinking on it a bit I came up with a plan. Considering the size of the stud gluing it back on probably isn't going to hold so I flipped the car over and using the Bolster pin as a guide, I drilled a "63 (0.0370) hole straight up through the center of the bolster pin and the car itself creating a perfectible centered hole. Then using a 00-90 Taper Tap I threaded the hole in the car and just started threading the tip of it into the bolster pin. By not cutting a full thread into the bolster pin and drilling a smaller than the recommended pilot hole the 00-90 screw will be a tight fit on the car the bolster pin will work like a Nylock nut and help keep the screw from backing out.

    After test fitting the screw i found that the threads on the screw were binding on the mounting hole in the joining car so I stuck the screw in my lathe and removed the top couple threads and part of the screw head.
    I tried to remove more of the screw head but the 00-90 x 3mm screw was just too short to hold properly so I ordered some longer 4mm, 5mm and 6mm bras screws to try out. Being longer and made of Brass it will be easier to grip and remove the upper threads and the head leaving just a stud sticking up like the orignal

    Pin is broken off on the car to the right

    Drilled and Tapped

    Upper Screw threads removed

    Test fitting Screw

    The screw is too shiny

    Screw painted Black

    Looks better
  2. Zscaleplanet

    Zscaleplanet TrainBoard Supporter

    Always appreciate your level of documentation, as well as your ingenuity obviously.

    Kurt Moose likes this.
  3. JoeS

    JoeS TrainBoard Member

    Love the creative solutions! Question now is your solution better than original ;)
  4. CNE1899

    CNE1899 TrainBoard Member

    Agree with what Lance and Joe said. Great work!(y)

  5. tjdreams

    tjdreams TrainBoard Member

    Thanks for the Compliments Guys.

    At this point I'm going to have to say Maybe. I need to do some more testing.

    Other than the non prototypical screw head being visible it defiantly worked. I tried to run them at the Great Scale Model Train Show this past weekend with "Tried" being the optimal word. After cleaning the paint out of the pin pockets as described in the Z track video the cars swiveled back and forth freely and ran fine on perfectly Flat track but they kept coming apart as they crossed over the expansion track used to connect one module to the next And as they entered & exited the Mountain crossover module where one track raises up and over the other which dips down. The slight up and down movement forced the upper pin pocket to rise slightly causing it to slip up and off the pin which resulted in the cars coming apart.

    Running empty the well cars came apart more often than those with double stacked containers. Adding a small weight hidden in the end of the container helped keep some of the cars from popping apart at the expansion tracks but the longer the train the more it seamed to pull apart. The only one that didn't pull apart at the Mountain Crossover Module was the one I connected with the screw.

    I have a few ideas on how to fix the problem and do away with the unsightly screw heads but I'm still waiting on the additional brass screws I ordered to arrive.
    I think they must be on one of those "Slow Boats From China".
    Kurt Moose, CNE1899 and Kez like this.
  6. SJ Z-man

    SJ Z-man TrainBoard Member

    David, you’re on the right path. Been there! Most raw machine parts increase friction so a micro drop of teflon lube?
    These cast cars look great but even with large radii (13-15”) we’ve had similar issues.

    Use a setscrew to get rid of the head issue, if you can find a long enough one (might be easier to find in mm)
  7. tjdreams

    tjdreams TrainBoard Member


    Mistakes Happen.
    I had 2 other sets where the same cars kept pulling apart so this weekend I decided to remove the pin, drill and tap them too while I was at it. But unfortunately things didn't go as planned. Like last weekend not wanting to risk damaging the car by clamping it in a vice i held it on the drill press table by hand eyed it up and drilled out what I thought was the center. Wrong. I'm not sure if I eyed it up wrong, if the drill bit wandered or maybe I moved my hand, but as you can see the Hole is not centered
    Their is no way its going to work as is.
    20230507_170822-C.jpg 20230507_170926-C.jpg
    Great now I got to find a way to fix this F---Up.

    I have 2 more cars that need to be drilled out so I decided to make a simple holding fixture and drill guide so i don't make the same mistake twice.
    off to the mill I grabbed a scrap of Aluminum and started milling a grove down the middle about 5 hundreds of a inch deep taking a little off each side until the car fit then I milled a cross slot to even up the end and use as a stop to hold the car from sliding.

    20230507_172921-C.jpg 20230507_172754-C.jpg
    Next I used a undamaged car as a guide to Aline the bit with the pin. Once I had it all aligned I used a bottom cut end mill to remove the pin then used a hardened 000 Center drill with a 0.20 point to start the hole before switching to a # 62 bit in a collet to eliminate any runout from the chuck and help prevent the bit from wondering. After drilling this one I double checked to insure it was in the right place then drilled a hole in the fixture so i can realign it again if I ever have to do this to another car.
    20230505_160926-C2.jpg 20230505_162227-C.jpg
    (Note; A clamp that holds the container and car down in the fixture was removed for the pictures.)

    After successfully removing the pins drilling and tapping the other 2 cars I have a plan on how to fix the one I f--ed up. I am going to order a 1.5mm bottom cut endmill and try to use it to mill straight down vs drill in hopes that a hardened milling bit will be able to cut straight down with out bending and following the existing hole like the drill bit does.

    The screws I ordered are still stuck on that "Slow Boat from China" But some of the other upgrade parts I ordered have arrived.


    Yup I'm adding sound and a FRED to this set.

    More updates coming Stay Tuned
    gmorider, Kurt Moose, HoboTim and 3 others like this.
  8. CNE1899

    CNE1899 TrainBoard Member

    Nice machining work. Sorry about your F-up.:(
    Good recovery as well.
    Might you be able to drill out a bigger hole and epoxy in a thick walled brass tube?
    My two favorite metals to machine are brass and aluminum.
    Have you checked out or
    The brass screws I use for smokebox clean-outs are from MiniTaps.

    Last edited: May 8, 2023
    Kez likes this.
  9. tjdreams

    tjdreams TrainBoard Member

    Adding Sound and a FRED

    While working on the replacement connecting pins a couple weeks ago I noticed a few characteristics about the setup of the well cars that would lend itself nicely to being able to adding power pickup and run wires between cars unseen.
    Which got me to thinking. Every time a intermodal train came by when I was working down at Ravens Stadium We could hear the Flange Squeal and the Clickity Clack of the cars crossing the turnouts and road crossings from a long way off. and every now and then the very distinctive sound of a car coming by that had a wheel with a flat spot.
    And that's all it took I ordered a SoundTraxx Sound Car Decoder, a Keepalive, a Speaker and a red LED.

    Taking some time to plan this out I decided to put the parts in the bottom containers only, mainly to keep a low center of gravity but also because here in Maryland they are still using the Baltimore and Potomac tunnel which is too low for Double stacked containers, The tunnel first opened in June 1873 nearly 145 years ago. Trains were not that tall back in those days.

    Getting started the decoder fit in a container with and length but was too tall so I removed the shrink wrap and sanded the edges of the decoder down a little till I started to see a glint of the traces on each side of the board then I cut a slot in the bottom of the container floor for the edge of the decoder to fit into then using some Liquid Tape as a glue I glued the bord on its side to the container floor.

    Next using the car as a guide I cut out a small spot on the front and back end of the container for the wires to fit through Being under the deck they can not be seen from above
    20230507_163844-C.jpg 20230507_152804-C.jpg

    With the cars flipped upside down and the wheel sets removed you can see how the wires fit nicely between the truck and underside. Next I soldered a wire to a wheel wiper installed that under the bolster pin and fed the wire through the same hole on each end of the car then reinstalled the wheel sets making sure the insulated wheel were on the appropriate sides.
    20230507_154802.jpg 20230507_160148.jpg

    Likewise the Keepalive was a little too tall so I removed the shrink-wrap and covered the bottom of the circuit board with a piece of Kapton Tape. I also cut one of the angle braces on the bottom of the car to give clearance for one of the larger chips on the bottom of the board. Next I fished the connecting wire through the openings from one car to the next. running one wire on each side of the bolster pin mount.

    For the speaker i wound up using a TCS #1699 16mm x 9mm Micro WOWspeaker. After continuing the speaker wires through to the next car I cut a hole in the bottom floor of a container sealed the speaker in and wired it up. I used some black sewing thread to bundle the wires and keep them in place along side of the decoders.

    20230507_141649.jpg 20230507_161504.jpg 20230507_161623.jpg

    I plan to glue a couple small magnets inside the container shells and to the bottoms which should keep them in place while running, yet allow me to lift them off to access the decoder if necessary. I still need to make the FRED mount and connect the wires to it but that's a job for another day.

    gmorider, CNE1899, Kurt Moose and 2 others like this.
  10. tjdreams

    tjdreams TrainBoard Member

    Its no big deal it happens sometimes.

    I'm ordering a 1mm,1.25mm and 1.5mm bottom cutting end mills and am going to experiment on a old chassis to see if i can mill down straight vs following the existing hole like a tapered point drill bit of that size will. If it works I plan to use a tiny bronze/brass bushing and a longer self tapping screw to go all the way through to the bottom of the bolster pin which should hold everything together in their proper places.

    Yea I've bought from both Mini Taps J.I. Morris before, but $26.90 + shipping and tax VS $4.99 + free shipping from China. Well Slow Boat from China it is.

    CNE1899 and Kez like this.
  11. gmorider

    gmorider TrainBoard Member

    Model railroading. It's not just a hobby. It's an adventure!
    Kurt Moose and CNE1899 like this.
  12. tjdreams

    tjdreams TrainBoard Member

    Weekend Update

    I had some free time yesterday so I got started on the FRED or End of Train Device. I started with a 2.5mm Square strip of Styrene, cut off a small piece then drilled a no 70 hole through the middle at a slight angle, notched one end so the Red LED would slide down in the grove with the wire sticking through the hole, Next I cut a couple notches in the other end so it would fit over the end of a AZL Labs coupler.
    At this point it was getting difficult to hold onto the coupler for test fitting with out getting my big fingers in the way so I mounted the coupler in a old broken 89' flatcar truck. The long neck with fictional coupler box on the end made a nice convenient way to hold onto the coupler After test fitting and a little more trimming I used some UV Resin to fill the hole above the LED and to attach it to the coupler. I also wired the led to a 1.5v battery to keep it lit while I was working on it. I should be able to run the wires back under the truck above the axles and into the notched end of the container and connect it to the decoder. But first the size looks a little too big to me so I'm going to try to sand down the sides of the housing a little and paint it.

    20230514_100528-C.jpg 20230514_100909-C.jpg 20230514_101012-C.jpg

    20230514_103254-C.jpg 20230514_115442-C.jpg
  13. tjdreams

    tjdreams TrainBoard Member

    A little sanding and paint really changes the appearance

    20230514_132826-C.jpg 20230514_132929-C.jpg
    Kurt Moose, CNE1899 and Kez like this.
  14. JoeS

    JoeS TrainBoard Member

    Oh wow! That’s gonna be so cool to see at the end of train! Nice work!
    CNE1899 likes this.
  15. Kurt Moose

    Kurt Moose TrainBoard Member

    Wow, cool detail right there!(y)

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