TheRailwire
General Discussion => Product Discussion => Topic started by: Bill H on July 09, 2017, 04:40:26 PM
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Group,
By yoke I mean the plastic part immediately attached to the motor slipping on the motor shaft. Has anyone found a lasting cure for this? Short of buying a new motor assembly? I tried CA, it worked for a while, but eventually loosened.
Kind regards,
Bill
changed joke to yoke in title -gfh
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A good two part epoxy like Loctite used in place of the CA should work. Clean any oil or grease that may be present.
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Epoxy and you may want to rough up the shaft a little to give it something to grip.
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That coupling cracks causing the slippage. I have several of these - seems like a common problem on them (and surprising type of a failure for Kato).
That plastic doesn't take glue well (and I like to over-engineer things anyway). I took a piece of thin-wall brass tubing slightly larger than the small diameter part of the coupling. I then cut teeth on the end of the tube (making a miniature hole saw). Using that "tool" I created a circular groove in the coupling. Then I sliced a short piece of the same brass tubing and glued it into the groove (using CA glue). That makes it a permanent repair since now the cracked plastic part has a brass-reinforced collar. When the coupling is not installed on the motor shaft, it fits tightly again.
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Pete,
How about a picture
Thanks
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That coupling cracks causing the slippage. I have several of these - seems like a common problem on them (and surprising type of a failure for KATO)
Pete,
Checking my RDCs all four I have -have both couplings racked, but this is the only one that is slipping on he motor shaft. Indeed a very common problem.
Kind regards,
Bill
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Budd sternly warned RDC owners that pulling other equipment with them would void the warranty. Perhaps Kato should have done the same?
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Pete,
How about a picture
Thanks
Yeah, I know, that would be helpful but I didn't take any photos. :oops: Next time I fix one of those I'll take photos.
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Budd sternly warned RDC owners that pulling other equipment with them would void the warranty. Perhaps Kato should have done the same?
I recall my reading about this several years back. I have a number of these and none are showing the problem Y-E-T.
I have not tried running them with trailer cars. Usually, I operate them in pairs, which the prototype's builder allowed.
I seem to recall that the M&StL used to use them to pull trailer baggage cars all the time. M&Stl had problems with them, which Budd repaired a few times as a courtesy, but kept telling M&StL that it would not continue to repair them if it were going to keep pulling baggage cars with them. Eventually, M&Stl sold them to the C&O. If the C&O used them to pull trailer cars, I have never seen a photograph of it.
I did see a photograph that showed a CRI&P RDC's pulling a boat tail observation that had been converted to a passenger/baggage combine. The baggage end was the observation end. That would be considered funny by many, in fact, I recall a snide comment in the magazine's caption of the photograph. You must consider, though, that the only door for passenger access would have been at the opposite end. Had CRI&P put the baggage section at the other end, there would be no door for passenger access to the observation end. The photograph was taken in Kansas.
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I did see a photograph that showed a CRI&P RDC's pulling a boat tail observation that had been converted to a passenger/baggage combine. The baggage end was the observation end. That would be considered funny by many, in fact, I recall a snide comment in the magazine's caption of the photograph. You must consider, though, that the only door for passenger access would have been at the opposite end. Had CRI&P put the baggage section at the other end, there would be no door for passenger access to the observation end. The photograph was taken in Kansas.
Or, you could run the RDC as the observation car:
http://bcoolidge.com/Amtrak_71-75_Boston_Pix/%27The%20Night%20Owl%27%20with%20RDC%2072%20Back%20Bay%20Station%2010_72Edited.jpg (http://bcoolidge.com/Amtrak_71-75_Boston_Pix/%27The%20Night%20Owl%27%20with%20RDC%2072%20Back%20Bay%20Station%2010_72Edited.jpg)
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Or, you could run the RDC as the observation car:
http://bcoolidge.com/Amtrak_71-75_Boston_Pix/%27The%20Night%20Owl%27%20with%20RDC%2072%20Back%20Bay%20Station%2010_72Edited.jpg (http://bcoolidge.com/Amtrak_71-75_Boston_Pix/%27The%20Night%20Owl%27%20with%20RDC%2072%20Back%20Bay%20Station%2010_72Edited.jpg)
Push-pull?
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Does anybody have a picture of what this "yoke" looks like? Sounds like more than a few of these are around with this problem. Maybe time for a new one that stays together. :)
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EDIT: I was going from memory and I didn't remember correctly.
I just take a quick peek at the RDC universal coupling (yoke) and it is different that the one if the photo below. The RDC driveshaft has a smaller diameter ball on its end and the coupling also allows the shaft to move in and out of the coupling. So the part shown below is not a good substitute. Similar, but different. :(
It is the sea-foam green colored part. They are still available from Kato, as a part of the worm assembly - they don't sell those separately.
[attachimg=1]
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It is the sea-foam green colored part. They are still available from Kato, as a part of the worm assembly - they don't sell those separately.
(Attachment Link)
Are both ends hex drives or is the assembled end a cross yoke type?
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Are both ends hex drives or is the assembled end a cross yoke type?
Cross-yoke type. The assembly in that photo is not for the RDC - I only used it to show the yoke part. I don't have the model handy but IIRC, both the worm and the motor ends have the greenish yoke and the (much longer) drive shaft doesn't have a hex-end. But it is not the shaft that is the problem - it is the greenish part - it splits on the metal shaft side.
This would take a bit more time consuming to machine than the washers/grommets you have made in the past. Especially in larger quantities. I'm sure you realize that the Kato part is injection-molded.
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3D printing?
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Cross-yoke type. The assembly in that photo is not for the RDC - I only used it to show the yoke part. I don't have the model handy but IIRC, both the worm and the motor ends have the greenish yoke and the (much longer) drive shaft doesn't have a hex-end. But it is not the shaft that is the problem - it is the greenish part - it splits on the metal shaft side.
This would take a bit more time consuming to machine than the washers/grommets you have made in the past. Especially in larger quantities. I'm sure you realize that the Kato part is injection-molded.
Yes Pete, I assumed that. I am machining just such a part for some of my configurations. Don't know that I will use it but the option will be in the kit bag, tried and proven. :) It takes a few special ground cutters and special fixtures but isn't the end of the world. It is more costly to make but if they are failing it becomes a decision of a few dollars less for something that doesn't work or a few dollars more for something that does. That's been my approach for pretty much my whole professional life, designing and building machines that work. ;)
I could probably manual run those pieces for under $5 each in lots of fifty or so pieces, with the tooling done, so max $20 for a four piece set. If needed in quantity it becomes a "big shop" job in a CNC machine. In the CNC it would be less (as much as half) IF the quantity is there to justify making the tooling and the set-up. That would probably start at a quantity of at least 500 pieces and better at 1000+. Those quantities might be hard to assure. Seems like an easy decision to me but not always obvious to the world who likes to buy their parts by the pound. ;)
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3D printing?
Not accurate enough nor the proper stress resistant/ tolerant materials. At least not that I'm aware of. Quite excellent for many cosmetic parts but not where there are press fits involved. This needs to press on to the shaft without overstressing the material which means the proper materials and then, with an interference fit and tolerances less than .001". I'm sure that's where the problem lies with the current part.
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$4 a piece?! That's crazy! Especially when you can currently purchase a pair of worms and bearings, with 2 of those yokes included from Kato for $4! Then just use the yokes and have bunch of spare parts leftover (which you could probably resell). Those worms are perfect for the LifeLike SW1200 upgrades (and those don't need the yokes).
Or I can do my fix for almost no cost (other than just some of my free hobby time).
The best option would be to lobby Kato USA to run a batch of just the yokes and have them sold as a separate part (for low price). They probably already know that those are prone to cracking, so that would solve a big problem for everybody.
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$4 a piece?! That's crazy! Especially when you can currently purchase a pair of worms and bearings, with 2 of those yokes included from Kato for $4! Then just use the yokes and have bunch of spare parts leftover (which you could probably resell). Those worms are perfect for the LifeLike SW1200 upgrades (and those don't need the yokes).
Or I can do my fix for almost no cost (other than just some of my free hobby time).
The best option would be to lobby Kato USA to run a batch of just the yokes and have them sold as a separate part (for low price). They probably already know that those are prone to cracking, so that would solve a big problem for everybody.
But all of the parts in the world when they routinely fail are of what value? :| ;)
But crazy, Pete? :? Making anything machined in a piece or two or twenty quantities, at any single digit price, is what's crazy. And I really shouldn't even offer to do it. But if it would help someone out I'm willing.
It's not crazy when you're the one who has to make the tooling, do the drawing, set up the machine, make them, package and ship them, two, four, or even twenty at a time. And holding real tolerances in the machining. But for a max of five bucks a known problem can be properly fixed using Delrin bar (not molded) at proper tolerance and it won't fail. That part from Kato, who produces them in the thousands and tens of thousands at a time and over multiple runs, which at any price has a reputation for failure pretty much every time, makes it worth... what? AND... given those quantities, I could make that part too and easily in that budget except for the "it breaks" part. ;)
What was being offered (offered, meaning there's no obligation to do anything :)) was a proper part using expensive tools, skills, and time and at a VERY legitimate price which, in these quantities could NOT be offered if I was actually trying to make even a meager living at it. If you've got someone who can or will do that at what seems less than crazy to you, I could use them as a supplier and at those prices could even offer a per piece royalty to whoever found them. But that supplier also has to be able to remain in business for the future orders, too. 8) There's a reason you can't get high tolerance parts, one or a few at a time, at mass produced in China (or anywhere else for that matter, including China) prices.
Calling that "crazy" drives me just a little crazy. ;) :D
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Sorry that I upset you narrowminded.
The amount of custom work required to make this part, and the price that reflects your craftsmanship is out of my price range, especially when I can fix the factory-made part for few pennies, or buy the original parts for half the price. So that is why I said that it seems crazy to me, but that is my opinion and might be a bit strong of a word. But that is how I am. Sorry.
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Not a problem, Pete. 8) The choice of words did hit me a little and it struck me as suggesting it was exorbitant for the work being discussed and at the level it was being discussed, basically one off custom machined parts.
I was throwing that out as an alternative in general to those who were experiencing what seemed to be a common problem, not a solution directed specifically to you. It wasn't suggesting that you or anyone else who had the wherewithall would or should use that as an alternative, just a very real option with a budgetary number and an alternative that I don't think exists presently. Another way to fix it, I think permanently, and at what cost.
Honestly, I don't necessarily want to do those things. I'm not one who is having pure fun, thrilled with my new toy, enjoying my newfound hobby machining. I do enjoy this work or I wouldn't be doing it but I'm not so enamored with making little parts because it's really old news for me, a big part of what I did professionally for decades. When I've offered it, it was when I saw something that looked like it could be done at a tolerable cost and I know the feeling of helplessness that some of these kinds of problems can present because I've been there. And finally, I only offer it when it fits easily some of the tools I have and I could coax the necessary part tolerance from. An option that I'm sure few have at their fingertips. That's all. 8) And all is good! :)
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Wow, we have some really touchy people here. I got down voted for stating my opinion and even for my apology!!
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$4 a piece?! That's crazy! Especially when you can currently purchase a pair of worms and bearings, with 2 of those yokes included from Kato for $4!
Pete:
Are you saying that the yokes on the worm gear set for $4 have the same inside diameter as the yokes on the motor - i.e. will fit the motor? Have you actually tried it - as you noted you had a different fix for your own RDCs.
Kind regards,
Bill
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Pete:
Are you saying that the yokes on the worm gear set for $4 have the same inside diameter as the yokes on the motor - i.e. will fit the motor? Have you actually tried it - as you noted you had a different fix for your own RDCs.
Kind regards,
Bill
Well yes an no. The motor shaft hole is the same diameter (since it is standard Kato motor), but the ball-joint part of the $4 part is slightly larger. I went back and corrected my original post. I was going from memory and now I actually checked both parts. So, the greenish yoke cannot be used for replacing the RDC yoke.
But I just opened up another one of my RDCs and fixed 2 cracked yokes. I'm planing on covering the procedure in a short magazine article, but in the meantime please PM me if you want some photo-instructions.