Loose motor magnet

[Zflyer]

I have just returned from the field having had a shaft come loose on the motor, Overlander T2830/09. Having taken the motor out and upon examination it appear that one of the magnets has come adrift. I note from an earlier topic epoxy has been used to reattach the magnet. I am considering doing the same. Anyone know if its been successful or recommend an alternative?.

[Kevin Fairgrieve]

I used some of this on a motor that had displaced a magnet. Three years later it is still going strong.

Loctite

Just my 2p worth.

 

Kev

[ken anderson.]

Hello ZF...I've read to your pm..

 

Ken Anderson...ne...1...epoxy dept.

[Andy Stephenson]

This kept happening on a 60 glow equivalent size motor . I pushed several loose magnets back into place and flooded it with cyno, they never came loose after that.

[Philip Lewis 3]

Problem with epoxy is it has a very low melting point (low enough to melt with a hairdryer) so if your motor gets hot it is likely to happen again, the loctite or cyno solutions are likely to be far better alternatives. 

[Outrunner]

15 hours ago, Philip Lewis 3 said:

Problem with epoxy is it has a very low melting point (low enough to melt with a hairdryer) so if your motor gets hot it is likely to happen again, the loctite or cyno solutions are likely to be far better alternatives. 

But if your motor gets hot the magnets are ruined anyway

 

[PatMc]

23 minutes ago, Outrunner said:

But if your motor gets hot the magnets are ruined anyway

 

That depends on the how hot - most commonly available epoxy will almost certainly give up (not melt) at a lower temperature than would damaged the magnets.

[Paul De Tourtoulon]

Is it worth the risk crashing, grilling your controller or worse burning out your battery and setting Britain on fire for £19 ?.

[Masher]

Could get a couple of 148's for that 😗

 

[PatMc]

52 minutes ago, Paul De Tourtoulon said:

Is it worth the risk crashing, grilling your controller or worse burning out your battery and setting Britain on fire for £19 ?.

Yep, the risk is between no more than with a new motor & infinitesimally greater but only because someone has suggested a greater risk exists.    

[Geoff S]

17 hours ago, Philip Lewis 3 said:

Problem with epoxy is it has a very low melting point (low enough to melt with a hairdryer) so if your motor gets hot it is likely to happen again, the loctite or cyno solutions are likely to be far better alternatives. 

 

What do you set as a low melting point?  We used to pot electronics in epoxy for the short range telemetry systems in gas turbines and they were tested at 125 deg C and there was certainly no signs of any softening.

[PatMc]

Geoff, were you using modelers quality, off the shelf epoxy ? 

Edited August 27, 2022 by PatMc

[Don Fry]

I would say, don’t bother. 
Geoff in work will likely be in a professional environment, materials scientists on call, who access data sheets for how long cured epoxy can take a certain temperature without degrading? Aircraft grade products have data sheets. That why they COST. You don’t REALY know these numbers with household glues. But epoxies common or garden, can start to degrade at 80°C. How long they hold up is not known. What is the rate of loss of performance?
I reckon the maget will last better, but a guess, look up Curie Temperature for neodymium magnets (temp where the material loses it magnetism), and it can be as low as 100°C. Also no data on what that magnet is in that motor. 
Might work, might not. Shell out for a new motor, probably end of problem. 

Edited August 27, 2022 by Don Fry

[Andy Stephenson]

Please, guys, enough about epoxy, CYNO WORKS.

[Don Fry]

If you substitute cynoacrlate for epoxy, and read it with the substitution it’s still correct. Even the temperature is not faraway. 
It worked for you, it might not work for a different brand. No data. 

[PatMc]

23 minutes ago, Don Fry said:

I would say, don’t bother. 
Geoff in work will likely be in a professional environment, materials scientists on call, who access data sheets for how long cured epoxy can take a certain temperature without degrading? Aircraft grade products have data sheets. That why they COST. You don’t REALY know these numbers with household glues. But epoxies common or garden, can start to degrade at 80°C. How long they hold up is not known. What is the rate of loss of performance?
I reckon the maget will last better, but a guess, look up Curie Temperature for neodymium magnets (temp where the material loses it magnetism), and it can be as low as 100°C. Also no data on what that magnet is in that motor. 
Might work, might not. Shell out for a new motor, probably end of problem. 

I would use a version of Loctite as Kevin suggested, you can check them by their published data sheets.

The Curie temp of neodymium magnets is actually higher for the cheaper types but isn't really an issue here.

   

Edited August 27, 2022 by PatMc

[Geoff S]

1 hour ago, PatMc said:

Geoff, were you using modelers quality, off the shelf epoxy ? 

 

No idea. It was a long time ago (early 90s) and I wasn't responsible for the potting - just for some of the design.  There were very few (or even no) temperature or G (20k G!) issues.