Microlighters

I have a potential problem. I have no idea if it has always been like this, but after a flight my gearbox on my Rotax 503 gets flippin hot!
I know they are meant to get hot but I cant touch it for long beacuse its so hot!!
Is this a problem or is it normal? How hot should it get?

Generally speaking,the average human hand can touch 60 degrees celsius for short periods but you will find it very uncomfortable. 65 degrees is not touchable for more than a very brief period and then it will make you sore. So if you can touch it at all then it is safe to say that you are on or near these numbers. 70 to 90 degrees is a nice number for most gearboxes and we consider 100 degrees borderline too hot. Here is a gross check that we use, spit on it when it's hot, if the spit boils, then it's too hot. If it simply evaporates relatively quickly and just leaves your DNA stain behind, then it,s OK.
If the gearbox is getting too hot, and the heat is being generated from within the box as opposed to heat soak from the combustion chambers, then you need to fix this soon as it will fail fairly quickly. Make sure that the box has the correct quantity of oil in it as a low oil level will contribute greatly to elevated temperatures and ultimately will cause elevated blood pressure.
In the case of the 912, the gearbox on this motor uses the same oil as the engine so whatever the oil temp on the engine is, then that is the temp you will get on the gearbox case. It is quite normal on these engines to measure gearbox temps from 80 to 120 degrees. If you want to be more scientific, a laser guided infra red thermometer works great for checking external engine temps.
Hope this helps

There is a heat strip that you can stick on the gearbox that turns in couler if it gets hot . Captain Biggels have them for sale.On this toppick is it possoible to fit a heat gauge to a gearbox .

A fluke multimeter has a temperature probe. Measure the temps and follow tandemtod1's advise

This seem to be a typical case of "sagte handjies, harde gat", (Just kidding), this seem to be a problem, I can not recall that my 503's gearbox ever got so hot that I can't touch it, do you perhaps know what the viscosity of the oil is that you have in the gearbox, if you try to move the prop sideways, does it have any play on the axle??

Luckily there's no pervert here who's tempted to pull the p!ss out of this one.

Tumbleweed wrote:Luckily there's no pervert here who's tempted to pull the p!ss out of this one.

Apparently all the perverts are on their way to Petit and Aeroden to watch Skin doing his 500hr flight kaalgat!

First pervert

Her gearbox does get hot but only on the long strokes

Thanks all of you who replied!!! Glad i got all the info before it turned pearshaped!!! Thanks again. So much valuable info on this site from everyone.
have a good weekend all!

Bushpig

oh yes i wont forget to spit on her gearbox and to check if she has enough lube!!

thanks again.

Sorry kalahari....... I use Caltex final drive oil. I can touch the box , but only briefly. ill check next time I fly if there is any side play on the shaft. I think ill drain the oil anyway and see if there is anything in the oil and replace with new oil.

... trust andy
blerry tramp

You are all a bunch of bush pigs ......... sis

Bushpig wrote:Sorry kalahari....... I use Caltex final drive oil. I can touch the box , but only briefly. ill check next time I fly if there is any side play on the shaft. I think ill drain the oil anyway and see if there is anything in the oil and replace with new oil.

Good choice ,

And if I offended anyone with my last comment,


















I dont care

you see ...

Gotta luv you Leftseat!!!