railandsailWhy this particular epoxy, and why this partcular color of their epoxies??
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I use Blue/Green Kneadatite for all kinds of modeling work, so I always have it around.
This product has lots of positive atributes. It has an incredible amount of adhesiveness, and it has a long working time. It can be worked with normal sculpting or dental tools easily, it is fully non-toxic, and it does not attack any plastic I have ever used it on. When fully cured it is 100% inert, and it does not change dimension when curing.
Loctite "Plastic Weld" two part epoxy would probably work as well, but it had a shorter working time and it is more difficult to shape.
-Kevin
Living the dream.
SeeYou190 Then put a small bead of Kneadatite Blue/Green epoxy putty where the gear meets the shaft and be sure to press the putty into the slots and/or holes. -Kevin
Then put a small bead of Kneadatite Blue/Green epoxy putty where the gear meets the shaft and be sure to press the putty into the slots and/or holes.
Why this particular epoxy, and why this partcular color of their epoxies??
Brian
My Layout Plan
Interesting new Plan Consideration
I hear a lot of suggestions to use Loctite.
When most people talk "Loctite", they are referring to one of three products, 271 "red", 242 "blue", or 290 "green". None of these are plastic compatible. I would never use one in a model. Also, they are intended to lock the threads of fasteners to prevent screw walk out. Not gears on shafts.
The correct LocTite product to use would be RC-609 which is specifically made for cylindrically fitting parts, but again, is not intended for plastics.
I have fixed this problem like this:
Just outside the gear seat area, make a hole, or file a shallow slot in the shaft. On the side of the gear, make a hole or file a slot. Put the gear into position. Then put a small bead of Kneadatite Blue/Green epoxy putty where the gear meets the shaft and be sure to press the putty into the slots and/or holes.
Allow the epoxy putty to cure overnight, and you will have a firm mechanical connection between the shaft and gear.
I just read back over this excellant subject thread, and remembered some things I had forgotten,....ah, memory recall these days
to the forum.
We don't close nuthin' around here unless it goes off topic or political.
However, there is no charge for you to start a totally new thread as old threads often have dead links and comments by people who have moved on.
Your first handful of post are moderated which means we never get spam. Don't just sit back and lurk, step up to the plate. Sometimes that means you find out that you knew less than you thought you did. That's a good thing.
Henry
COB Potomac & Northern
Shenandoah Valley
Just joined the forum only to say "thank you everyone." I stumbled across this thread today and learned so, so much!! I'm happy it wasn't closed. I enjoyed reading and learned from ALL the posts, 2011 or not.
When I was young, Pliobond was the best adhesive for strong resilient bond, or when some vibration damping was needed. The only real drawback was the stink, and if you spilled it on anything stainable that was pretty much it. But my grandfather loved it for general repairs and so did I.
It’s just not good for smooth metal shaft slip-fit into a slick plastic gear, at least not without thinning and very extensive ‘drying’ time as it can’t be applied as contact adhesive for that fit.
I was just always a fan of the rubber based adhesives due to their basic 'elasticity'
Think of Pliobond as industrial-strength rubber cement. It does not have the right characteristics for gear-on-shaft even if you get a reliable thin film on the two mating faces and press them together without twisting ... which you can’t.
Note that the ‘balloon trick’ referenced above is the equivalent of putting much better structured rubber molecules in the joint with the proper geometry to load them in compression without tensile separation on any part of the ‘bond line’ that finds itself loaded in tension...
It's "Pliobond", and it's too soft for that application. Tim Warris, of Fasttracks fame, recommends it for affixing his laser-cut tie templates under his style of turnouts.
PiobondWhat about this rubber based adhesive piobond??
To put in some potentially helpful material that was only partially addressed in the ‘old’ thread:
”Real” Loctite is an anaerobic-curing material, meaning it will only set up if the joint is not exposed to oxygen. An upset shaft may only produce this if it cuts corresponding ‘keyways’ in the gear, which may facilitate splitting, but the advantage is that it will not set up before the gear is actually pressed into the equivalent of perfect or interference fit.
Cyanoacrylate cures by exposure to moisture. That may be difficult to ensure in a tight joint. As noted the basic crosslinked ‘result’ is brittle and may not bond effectively to some materials (and I do think some of the Delrins are in that category) ... more on that in a moment.
Epoxies are time-delay chemical cure, so are ideal for mechanical joining ... but depend on a relatively thick layer of bond for full strength, very different from the situation with regular CA. For a shaft with gear you might want to open up some of the joint while keeping enough of the shaft OD and gear ID intact to preserve alignment in both ‘wobble’ and runout.
For shock loading, you want more of an elastic bond than an initially strong but brittle one. Epoxies inherently provide this; I believe it is a characteristic of at least some Loctite. I think the CA formulation that is loaded with tiny elastomer (rubber) particles is intended to provide elastic bond, and some of you with firsthand experience with it might comment. Notably, the stretched-latex-membrane technique that reanimated this thread is inherently both self-locking and highly elastic without ‘bond failure’ at all in torque loading.
There are surface-activating techniques other than mechanical roughing that can be used for better bond strength; perhaps the most applicable here would be to use an ‘activator’ in the hole of an otherwise-slippery gear to enhance “bondability” there. Has anyone here experimented with etching ‘primer’ for plastic pipe, or the ‘activator’ in one of those rear-view-mirror reattachment kits?
Now, the next fun thread will be about how to fix the situation when a gear does split...
You could get a knurling tool from Micro Mark but expensive for one shot. Not sure how to do this in home workshop. There are some videos on you tube about knurling. I did this a few times when I was a machine mechanic but on a larger scale.
I would rough up the shaft and each side of the gear near the shaft location and use five minute epoxy.
Red loctite might work between the shaft and inside the gear hole as I believe it expands a little when setting. I remember pulling a couple bolts many years ago that red was used in.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
I've found that the epoxies only have a limited time to stick to the plastic gears, particularly if they are put under heavy torque loads.
And I feel it is primarily because of the type plasic those gears are made from. The epoxy will stick to the shaft, just not the gear if I remember properly (been quite awhile since I worked with the problem).
I have been here on this forum for about 13 years. I can't tell you how many times I have read anguished posts from guys who have found that one of their gears has split on its shaft. It means a complete replacement of that shaft, or else a gear that will withstand the pressing into place without also splitting.
If you wrap a shaft with anything that will widen it, and attempt to press a used/old plastic gear onto that thickened shaft, you stand a greatly increased risk of splitting the gear. It may work, it may not. That is why using an epoxy or suitable adhesive is a better idea. The fluid will find voids and fill them, but also stick to surfaces such that the gear will no longer rotate on the shaft. If you split the gear, it will rotate freely and cause either no motion from the drive or a thumping and hitching motion in the locomotive.
Just sayin'....
About old threads being resurrected. Why the heck not? Maybe I have learned something in the interim, something that should be shared. Maybe I have since disabused myself about the efficacy of epoxies in this type of repair. Maybe someone else has an entirely different method that works. Maybe a new supplier has parts, better ones. Maybe there's a handy video since added to youtube that shows a workable solution, and shows it very well.
Why the heck not!?!?
What is this aversion to older subject threads?
We are not very far apart in our views at all. I agree that some threads are bodies of "how to" knowledge and timeless. I also agree that newbies and old timers too, sometimes miss the date of a thread. The post made a contribution to our knowledge and I said so.
I was gently calling his attention to the fact that not all old posts are still relevant. Obsolete is a good term and weighing in with a "me too post" in a thread started by someone who hasn't been in the forum for 10 years is just noise.
Admittedly, this post is noise too. Now back to our modeling.
railandsail rant over...ha...ha
rant over...ha...ha
Look at it this way, Brian, your point of view prevails since the forum does not lock old threads.
Alton Junction
Many subject threads are NOT about solving a particular problem, but rather they document various views, dwgs, etc on subjects. So they don't neccessarily go obsolete. And these are often valuable. look at the number of subject threads that have been rendered almost useless by the latest shenanigans by Photobucket.I find that many of us (particularly the younger folks) don't bother to look up any history of a subject, but just immediately go to posting a new but same subject....I guess I would call it the 'instant gradification' generation,. just pop it on your cell phone and get an answer. Or ask a question of your cell phone.
I grew up (now 75) going to libraries to do research. Granted the internet is a GREAT alternative to the old library, but there are lessons to learn from studying the history of a subject,...ie going into an unadvised war (how did it or they happen), etc, etc.
railandsail BigDaddy But it is a 6 year old thread. Just sayin'.... What is this aversion to older subject threads? There is often a lot of good information locked up in those older discussions,...that might get ignored if the person just starts a new subject thread. I often praise the person that takes the effort to explore what has come before on the subject rather then just creating his own new thread.
BigDaddy But it is a 6 year old thread. Just sayin'....
But it is a 6 year old thread. Just sayin'....
There is often a lot of good information locked up in those older discussions,...that might get ignored if the person just starts a new subject thread. I often praise the person that takes the effort to explore what has come before on the subject rather then just creating his own new thread.
I got a kick out seeing my old thread revived here, but I have long felt that the forum software should automatically lock a thread after one year of inactivity.
What often happens, as in this case, is that a new forum member will revive an old thread as his first post. Truth be told, he probably doesn't even realize that in his search he has uncovered an old thread. He provides advice or suggestions or other commentary for an issue that was long ago resolved. In this instance, I successfully solved my problem back on February 15, 2011 and said so in my then final reply to the thread that I had created. Case closed.
What I have often argued for is to start a new thread and reference the old thread, if need be, with a link to the old thread. It would be locked but still available to read, just not to reply. This would eliminate a lot of confusion, especially when it comes to giving advice on a long ago solved problem.
It would also prevent newbies from unknowingly reviving old threads.
That is a reasonable and novel contribution to the discussion. But it is a 6 year old thread. Just sayin'....
Instead or using messy glues or epoxies try this. I googled this problem and tried all other suggestions I could read on. Then I got an idea:
Clean both the gear hole and metal shaft with rubbing alcohol to remove all dirt and/or old glue. Cut a small piece of a latex balloon big enough to fit into the gear hole with just a small bit extending once the shaft is inserted. Use 120 grit sandpaper on the shaft part that the gear will be attached to, no more, no less. All you want to do is roughen up the shaft. (Do NOT roughen up the gear hole, just be sure it is very clean). Place the latex piece centered over the gear hole, then press the shaft into it. It should be a very tight fit, nearly impossible to move the shaft within the gear hole. If it is still quite movable, then the shaft is sanded too much (or worn) or the gear hole is worn from slippage). Try a double layer of latex to tighten the grip. If you don't succeed at this, keep trying. It didn't fit right the first couple times I tried it, but after I go it, I had great success.
I built a working model farm windmill with a reciprocating pumping rod gearbox at the top. The output gear slid too easily on the metal shaft and there was no clearance to apply any glue or epoxy. I could hold the pumping rod while the the gear slid on the output shaft. Now I can actually stall out the drive motor if I hold onto the pumping rod! It's enough torque to actuate a working handpump at the tower's base.
Hope this helps.
I have always gone by the advice; -If nothing else works, use green Loctite!
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I agree, Wayne, it may not be very strongly adhered to the metal or the slippery nylon (?) gear, but its actual structure filling the gap acts more like a whole bunch of those keys we were talking about, or maybe more like a weird-toothed inner gear in its own right that forces both the axle and gear to rotate fully synchronously.
Crandell
I think that regardless of whether you use Loctite or ca, neither is acting primarily as an adhesive but rather as a means of increasing the "fit" between parts - applied after the gear is in place, it's drawn into the minute and irregular gaps between the shaft and the gear's bore, creating a rough equivalent of an interference fit.
Wayne
bogp40 Congrats Rich. The use of CA is fine for the application of the machine shop/ structure. I would only like to add, that CA is a brittle joint. If this was to be used on holding a gear/ part that would see torque, shock and other stress, as an axle shaft for a loco, Epoxy or Loctite is a better choice.
Congrats Rich. The use of CA is fine for the application of the machine shop/ structure.
I would only like to add, that CA is a brittle joint. If this was to be used on holding a gear/ part that would see torque, shock and other stress, as an axle shaft for a loco, Epoxy or Loctite is a better choice.
I use a product that contains cyanoacrylate ester, so I refer to it as CA glue, rightly or wrongly.
Also, Loctite is a brand name for a variety of products, but I thought that the principal ingredient in Loctite adhesives was cyanoacrylate.
Which Loctite product are you recommending? Does it contain something other than cyanoacrylate ?
Thanks.
Modeling B&O- Chessie Bob K. www.ssmrc.org
Excellent! And you have your loco back in service, or will have shortly. Very good news.
SUCCESS !!!
Here is what I did. I lightly roughed up the metal rod surface with a metal file, then applied a coat of CA adhesive and inserted the gear. After letting the glue dry for several hours, I used the pointed end of an Exacto Knife blade to apply JB Weld epoxy on either side of the gear where it touches the metal rod. I let the epoxy set and cure overnight, then tested it today with the motor torque, and it works !
Thanks guys for all of your help and advice.