Hi All, I tested a new Pulso 2826-10 motor (same as Cobra) a few days ago and was most impressed with the neat construction and smooth running. It is very close to the good old AXI 2826-10 and around 1/3rd the price. It uses a 15 mm ball-race at the rear and 2 x 10 mm ball-races up front. I decided to change the shaft so that I could use a bigger collet type of prop driver with an 8 mm shaft. It comes standard with a bolt-on prop driver with a 6 mm shaft and although this could have worked, it was a little short to get the prop in place. This was all fine, but I managed to damage one of the front bearings in the process. No problem........I had some good Japanese 10 mm bearings so it would be easy to replace the thing. That was the idea anyway. The bearings were in so tight that I damaged the others getting them out.

On the E-Max motors it's real easy to tap out the bearings, so the question now is....how tight should these bearings fit?? I know that on engines, very tight fitting bearings can be a problem as the heat gets up. I need to re-fit the new bearings now and I can make a tool to get them in dead straight but if they are so tight then surely the running heat will expand the metal a and squeeze them a bit?? Anybody have any suggestions? Thanks.

Keith R

Thanks William, the youtube video is a bit big for me to download. Our highspeed internet is expensive here in Darkest Africa and I have a limit on my monthly cap. I don't have a real problem changing the bearings usually and I've made things to press them in properly. They are now replaced. I was just keen to hear from the experts and how tight the fit should be. Thanks.

Keith R

Kieth,

Sorry to hear that you cannot view that video because it is a good one. When you say you tap the bearings out I wonder if that is hammer and drift punch?? The way I do it is to use a press (or in my case I use my drill press - not running of course). In the case of my Scorpion motors (may be a relative of the Cobra motors) the bearings come out easily so they are not a tight fit.

- that video shows removing bearing from scorpion motors, but they are IMHO too free (at least on my 3026), I had to glue them after few flights ... what I see on video I would say it goes out too easy ... however Keith you can choose lower quality so you can download it quicker also on slow connection

- bearing goes much easier if you heat motor to 100 dergrees C ... but do it ALWAYS with DISMOUNTER ROTOR (heat will damage magnets) ... I did it many times and removed even glued, it goes easy, if you have troubles, you can take 5mm metal rod and cut it lengthwise and open to something like Y ... so you can insert it inside the motor in direction of that uncut side and as it goes in, it will open inside the motor so you can use it for pressing in opposite direction

- bearing should fit by only hand, if the case is still warm and bearing cold, if you need press stronger, you will need tool to push outer ring and not inner, you risc damage of those small balls inside if you need press it by inner ring, those small 10mm bearing anyway does not survive too long

- I found it is not bad to open new bearing and replace grease by some very good high temp type, for example I use metanova F 1,5 and close it back ... or you can use liquid oil, with aditives (for example that sold by scorpion), which can be used also without opening, but it need periodical reoiling becuase that oil goes slowly out (and I hate oil in electric model :- ))) )

-when you close motor back, you shoud set axial free play at least 0,1mm (that is minimal) - that is for motors withou spring inside, for example AXI and MVVS, or you should use only gentle press if motor has spring ... too tight axial fit can stall heated motor (that free play gets tighter as motor heats up - it can kill bearing and cause burn of motor during one flight)

Thanks for all the suggestions and pics. Thanks Igor, you actually answered my question about the bearings being too tight and then causing problems when the motor heats up. Where is the spring in the AXI and MVVS? I must have missed that one.

Keith R

O.K. Thanks Igor, that makes a bit more sense to me now. My Pulso seems to be good again. I had a couple of flights today and it behaved well. It looks a bit small for that 12 x 6.5 EW pusher from Dennis but it runs fine with it. The weather is cool here now so I'll see when we get to Bulgaria in the heat.

Keith R