Slipping yoke on Kato RDC

[MK]

3D printing?

[narrowminded]

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.  

[narrowminded]

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.

[peteski]

$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.

[narrowminded]

$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.    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.

[peteski]

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.

[narrowminded]

Not a problem, Pete.   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.   And all is good!

[peteski]

Wow, we have some really touchy people here. I got down voted for stating my opinion and even for my apology!! 

[Bill H]

$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

[peteski]

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.