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View Full Version : Stratus driver / fan gap too big


Scrub
06-12-2007, 11:15 PM
I had a hot start a few weeks ago. I replaced my clutch and liner now I can't get the gap between the fan and driver correct. The closest I can get it is .035". I flew it once with this gap and literally tore up the dampners.

I'm confident I have everything installed correctly. I trippled checked everything, re-dialed my fan (I hate that part) but for some reason my fan/engine(os91szh w/pump) assembly seems to be just a bit too low.


Any suggestions on how I can obtain the correct gap?

Thanks!!

DavidH
06-13-2007, 07:12 AM
Just changing the clutch and liner should not change anything.

When you did the above, did you take the motor off the bottom plate?
If you did, are you sure you replaced everything as it came off the plate?
Was there a shim that went between the motor and mounting plate?

You had the fan off the motor. Are you sure you replaced any washers that might have been between the fan and the front bearing of the engine. This washer would have been on the crankshaft against the front bearing, then the lower collet would have been next.

Run out of the fan has nothing to do with gap distance. So re checking the fan for run out was not needed.

My guess since it is an SZ with pump, that you assembled the motor back to the bottom plate incorrectly. Check which side the bracket that holds the pump is on the bottom plate.

If everything is correct above. Only way I know to reduce the gap is to use washers between the back plate and bottom plate to raise the motor.

David

Scrub
06-13-2007, 09:12 AM
When you did the above, did you take the motor off the bottom plate?
If you did, are you sure you replaced everything as it came off the plate?
Was there a shim that went between the motor and mounting plate?
David


Thanks for the reply David. After the hot start I didn't disassemble or adjust anything form the lower assembly. I only seperated the lower and upper halves and removed the clutch stack. I'm positive I assembled everything correctly. After noticing the larger gap I even reviewed the manual to insure I put everyting back the same way. I don't have any shims between the motor and mounting plate. I do have the stock OS thrush washer between the fan and the front bearing.

After destroying the dampners on the first test flight I decided to remove the fan and re-dial just incase, re-assembled the motor mounts and bottom plate but for some odd reason I still couldn't achieve the same gap I had before the hot start.

The only thing I can think of to correct the gap is to add a something like a .015 washer under the fan.

Wayne
06-13-2007, 04:11 PM
My fan gap on one of my machines increased this year also, and it took a few days to figure it out.... After a mild crash (didn't break blades, how bad could it be....) I replaced the metal A frame part in the rear since that was bent, fixed my servos, and flybar, put new skids on, and thought I was good to go. It flew fine, but the gap for some reason was not the same, more like 0.035 or so. After a lot of looking, when I hit the ground feet first I put a very slight bend in the clutch machined aluminum part that holds the clutch assembly to the frames. (this is the sealed bearing/block right below the actual clutch) After a bit more looking, I saw that the carbon plate that holds the motor in place was slightly busted.. (Not enough to see at first...) After replacing those I'm as good as new.

So, in my case, and I think almost all cases, if the fan gap increases, you might want to check to see if something got bent/broken!

Wayne
www.flymha.com

So, is there any chance you may also have had a real hard landing that may have tweaked those things?

Scrub
06-13-2007, 04:48 PM
Thanks for the response Wayne. When I removed my clutch stack to replace the lining I did inspect all items necessary to remove them, upper and lower clutch plates and bearing blocks, etc. Using a feeler gauge I measuerd the gap between the driver and the lower clutch plates and that was fine as well. I haven't crashed (knock on wood) in awhile and the gap was fine until the hot start.

I can achieve the correct gap but then the holes to mate the upper assembly to the "A" Frames don't match.

I think I'll just try adding a .015 washer, if I can find one, under the fan to raise it.

.........funny I was just thinking, wouldn't it be crazy if after I add that washer the gap would turn out to be .015" to high.

wish me luck!!