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Post by tjdreams on Mar 5, 2023 21:07:10 GMT -5
Back in November I had one of my favorite Z scale Locomotives running on our layout at a show. It had been chugging along with out issue for a couple hours when another train on the same track had a breakaway leaving its cars behind. So we throttled down, reversed direction and started to back the runaway loco's up to reconnect with the cars it had left behind. No big deal it had happened a time or two before and the Challenger had no problem pushing its string of cars back. But wait My Challenger was not moving. I walked around the layout to where it was and as I got closer my heart sank. I could here the very distinct sound of a motor spinning and gears grinding but it wasn't moving. Yup something inside let go. Forward or reverse no movement just the sounds of a motor spinning free. The last run of my ill faded Challenger Just minutes before it's catastrophic failure. Fast Forward to last weekend when I decided it was time for me to do a exploratory. Taking it apart to get at the motor and drive train proved to be a real challenge. Several of the screws appeared to have paint on the threads which effectively Loctite them in. I was able to get them out but I wound up stripping out the Phillips heads on a couple of them in the process. Fortunately they are standard M1.2 screws which are available on Amazon. Then as I removed the rear truck/motor assembly from the boiler the Worm Wheel and Worm Wheel Shaft fell out on the desk. Which gave me a good idea of where the problem was. This being my first time disassembling a Challenger I can only guess at some of this but, It appears that the Worm Wheel Shaft was held in place between the side supports with some sort of rubber like glue. The remnants of which can be seen around the edges of the holes which are now egged shaped. Judging from what I'm seeing I believe the Glue failed to do its job which allowed the Worm Wheel Shaft to partially slide out of its mounting. Only being supported on one side the Shaft wobbled around egging out the hole till it was big enough that the Worm wheel (Gear) shifted to the point that it was no longer meshing with both the Worm Gear and Axle drive gear at the same time. The orignal Worm Wheel Shaft sitting crooked halfway in the egged out mounting
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Post by tjdreams on Mar 5, 2023 21:18:49 GMT -5
Here you can see the remanence of the rubbery glue around the edges of the egged out holes. Being that this is a rare Brass Challenger that sold out long ago I seriously doubt if anyone is going to have a spare rear drive truck/motor assembly they want to sell at a reasonable price. I would almost bet its more than likely others who have one of these may be experiencing the same problem. SO . . . . .... Stay tuned while I put on my Doctors Attire and take on the roll of Dr. Rudy Wells We can Rebuild it We have the Technology We can make it: Better (sounding) Stronger (no glue) Faster (DCC Decoder and keep-alive) We can bring it back to life!
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Post by Kez on Mar 5, 2023 21:29:04 GMT -5
And after this, my GS3 Daylight!
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Post by cwrr on Mar 5, 2023 23:11:13 GMT -5
Dang, sorry to hear about your Challenger! That's a heartbreaker for sure, ugh! Hopefully it doesn't turn into the "Six Million Dollar Loco"!
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Post by tjdreams on Mar 5, 2023 23:17:25 GMT -5
After thinking about the problem for a few days and taking lots of measurements I came up with a basic plan. Drill out the holes and make a new larger Shaft.
And so the Surgery Begins.
Fortunately the mounting holes were not egged out too bad. Using a set of soft plastic jaws I clamped the chassis to the mill table on its side and used the Worm Wheel Gear on a 1.5mm gauge pin in the chuck too center the gear between the worm gear and the drive axle gear. I must have clamped re-clamped adjusted and re-clamped it at least a dozen times before I got it to a point where I thought I could work on it and that's when I realized I had clamped it on the wrong side. 4 hours waisted. It took me another 2 hours to get it flipped over clamped and realigned again.
In order to insure proper alignment I was going to have to drill straight through both sides in one setup which is why I had to flip it over. The side with the smaller hole needs to be on the bottom. The hole on the right side needed to be enlarged to a 1/16th (0.0625") diameter. Just 0.0034 larger than the orignal hole. But a drill bit that small is going to want to wander and not stay true when going through that egged out hole. So I used a bottom cut 0.0625 diameter endmill to bore through both holes. The left side however needed a slightly larger 1.7mm (0.0669") to fix the egged shaped hole. Not having a 1.7mm drill bit or end mill I resorted to using a 1mm boarding bar to enlarge and true-up the hole. Happy with the results I cleaned up the mill put it away and got out the lathe for the next step.
Frustrated with my mistake and finally making progress I totally forgot about taking pictures of the setup.
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Post by tjdreams on Mar 5, 2023 23:30:53 GMT -5
With my Dr. Rudy Wells Lab coat on I went to work making a new Worm Wheel shaft. It took me a couple try's to get it right but I was able to turn a new brass shaft on my mini Lathe. The new shaft is 0.1800" long with several different diameters along the shaft The head on the end was turned down to 0.0955 D x 0.0215 L next a 0.0175 long section was turned down to 0.0667 to match the hole and thickness of the left side Next a 0.1005 section was turned down to 0.0635. then a 0.0175 section turned down to 0.0625 to match the thickness and diameter of the hole on the right side and the final section was turned down to a slightly larger 0.0634 diameter and rounded off. With the small end of the shaft being .0009 larger than the hole in the side mount it can be popped through the hole which should keep it from coming out on its own. Just like closing a snap on your coat. I know all those dimensions probably sound confusing to some, and the dimensional changes along the shaft are so small they are not visible in the photos so hear is a eradiated drawling showing the basic shape of the new worm wheel Shaft. And a picture of the new shaft in place
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Post by tjdreams on Mar 6, 2023 0:09:35 GMT -5
On to the next step Other than a little wear at the outer most corners on a couple of the teeth the worm wheel gear seamed fine. But the 1.58mm hole in the Wheel gear needs to be enlarged to 0.0645 +/- so it will spin freely on the new 0.0635" shaft. Again worried that a drill bit that small could easily wonder off center. And anything less than a perfectly centered hole would have the gear Wobbling rendering it useless. I chose to mount the gear in a small Pot chuck on my lathe and use a 1mm micro boring Bar to increase the size of the hole. Which I'm Happy to say Worked. Left side New shaft, Middle failed attempt (too short) Right orignal Shaft Bottom Gear with enlarged center hole Worm Wheel and New Shaft Snapped into place No Glue needed
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Post by tjdreams on Mar 6, 2023 1:05:50 GMT -5
After test fitting the head of the shaft was a little closer to the flange of the wheel than I liked so I put it back in the lathe and trimmed a little off both thickness and diameter then rounded over the corners. With everything looking good so far Its time to find out if the patient will live. I've ordered some Birchwood Casey Brass Black to blacken the New Shaft, and a new Sound Decoder So final Re-assembly will have to wait for the post office to deliver them and the new screws from Amazon
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Post by cjhayes2424 on Mar 6, 2023 10:16:57 GMT -5
Ausgezeichnet! Thanks for posting this!
Cjhayes
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Post by husafreak on Mar 6, 2023 11:00:54 GMT -5
Thanks for the description and pictures of your work, fascinating. Also for those of us with nothing but drill bits (no lathes or mills) it is good to know the limits of our tools. It would be a shame to attempt a fix and ruin such a special loco. Should I say this failure happened to the right person? Good job!
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Post by BAZman on Mar 6, 2023 13:03:26 GMT -5
Hans brought the prototype to a Zmod.no meet in 2008 that I was at. A wondrous mechanical marvel! But it drives only the inward drivers (as shown) and pushes the front complex articulated truck before it. How could this mechanical monster run on 195/220 curves? Not well . . .at all. Even on straights. A few years later, they were released for sale. Many of us bought them all up. Many of us have insane intentions an took them apart to put DCC/Sound in, knowing there are no spare part, no going back.
This takes the cake though! Well thought out and masterfully implemented.
Laos Thek of ZoCal was a jeweler, always trying to make small drive mechanisms (the concept long before SeaRails) and even a working Shay (you’ve all seen those crazy side open crank/piston shaft links). I’ve been in many clock and watch manufacturers replicating ‘Great Grandpa’s parts from the turn of the century, then reshaping them, as you did, to Regulate accurate timing.
Well done!
Oh, BTW: that YouTube vid WAS smooth as a well running watch !!!
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Post by tjdreams on Mar 6, 2023 20:18:26 GMT -5
Thanks for all the compliments everyone.
husafreak I'm still very much a beginner on the Mill and Lathe. I only just recently learned how to setup and use a boring bar had this had happened a year ago there is I good chance that I would have just screwed it all up trying to drill it out with a hand held Dremel
Jeff Its funny that you mention a Shay with working crank, side rods, and pistons. That just happens to be one of my other projects. The skills I learned while turning the Crank Shaft for my Shay project came in handy while making the Worm Wheel Shaft.
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Post by cwrr on Mar 7, 2023 0:15:25 GMT -5
Wow, just WOW!!
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Post by Deleted on Mar 7, 2023 1:23:03 GMT -5
Wow again ... At the present time, the smallest working model with live steam is N scale. I believe that in a future somebody will try to make it in Z ?
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Post by sjl on Mar 7, 2023 8:11:39 GMT -5
This is both massively impressive and a bit daunting (for those of us who had thoughts of buying a Big Boy or other big steam someday).
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