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Reisenauer gearbox assembly problem.

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Hi,   My Reisenauer micro gearbox was mounted on to a cheaper 2838 3600kv inrunner for use on my 1900g Claymore F5J glider. 

I followed the instructions, first carefully cleaning the mating surfaces, then using Loctite 648 compound to fix the "hi-torque" pinion gear to the 3.17mm shaft. 

A feature of this motor (usually used for model cars, I guess), is that it has a flat machined onto the shaft. 

All appeared to go well.  Test runs were satisfactory and a day's outing with around 16 launches on the glider went without any hitches (at least as far as the motor/gearbox was concerned).     

Today, some two weeks after the gearbox was fitted to the motor and two seconds in the first launch/climb the pinion gear became unfixed and now rotates on the motor shaft.  

I don't know if there is a better choice of fixing compound for this application than Loctite 648 or whether the flat on the shaft has any effect on the joint strength.  I don't really know how hot the motor is getting.  From the smell of it on landing, and the appearance of the windings etc now it's out, I have no reason to believe that it has overheated.  

Before I have another go at fixing it, is there something that I could do to improve the fit of the pinion?  



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I've only assembled a couple of gearboxes but I've used 648 without any problems but there's no flat on the motor shaft. If the pinion is over that part of the shaft that has the flat you might always get problems, it's not designed to fill such a large gap. I've also read where someone used an old bottle of compound retainer and the pinion would let go easily, a new bottle of 648 solved the problem as I remember.

Here's the data sheet if this helps http://www.henkeladhesivesna.com/aam/Retaining_LT3770_AAM_Chart_Interactive.pdf

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John Minchell

I have heard of locking fluids going off. 

I have also heard (in the car racing world) of filling the flat on the shaft with solder, shaving the excess off with a sharpened brass tube of 1/8th ID and thus giving the locking compound a full 360* to grip onto and the solder won't move either because it is trapped by the ID of the gear and the flat on the shaft. 

Might be worth a try as a last resort as long as you can keep the heat out of the motor bearings.

John M

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If the motor/ GB was bought as a unit from a retailer, I'd explain to them the problem and see what they might suggest. I haven't seen the 'fill it with solder' option suggested on any threads I've read, so I can't really comment other than I can see that being a difficult job to get right. It sounds possible but it's a job I'd probably mess up, lol, good luck if you try.

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Thanks for your suggestions....     It's all because I'm cheap...  not bought as a unit. 

It crossed my mind to fill it with solder,   but then, why not solder the pinion on to the shaft?

Lots to go at.     

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Nothing wrong with trying cheap options, just a pain when they don't work. HET motors are ok, I've had front plates come unglued due to excessive heat, my fault for over propping or too long a flight/ motor run but otherwise they're ok. My problems with HET are on direct drive and not GB driven just to be clear. I like Mega motors, if you bend a shaft or burn it out you can send it for repair rather than throw it in the bin, but they are more expensive. 

I think a likely problem with soldering or attempting to permanently fix the pinion would be whether you'd get any interference with excess solder, and should it break it's bond you are risking damaging the gears of the GB if the solder breaks up. I'd be in the 'You don't want to do that' camp anyway, retaining compound has been developed for a reason.

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Hi Dave - the mating surfaces between the pinion and the motor shaft have to be scrupulously clean. 

Personally I always use acetone for this job to remove any traces of oil / grease.

Loctite 648 certainly has a finite shelf life. Expiry date is written on the bottle somewhere - old material will not work as well so always use material within its shelf life.

Finally  make sure you use a soft start and a soft stop when running the motor. this helps to give the GB and pinion an easier life.

Hope this helps.



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Thanks to All for your help.  

I have re fixed the pinion gear using the recommended method (without doing anything with the flat, this time).    

The Loctite does have a date of 09/20, so is near to it's end. This time I gave it a good shake and ran off some before using it. I gave it more time to cure before running the motor gently and will leave it 24hrs before running near full load.  



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