Electriceddie

Hello OS Max Support,

I have a brand new OS Max .FS91 II Surpass engine. I went to break it in on a test stand and when I put the prop on I noticed there was a problem, the prop was spinning freely. Upon further examination I found that the woodruff key was missing from the drive hub. I ordered a new woodruff key from "Tower Hobbies". When the woodruff key arrived I put it in the shaft and added the drive hub. However after I placed the prop and spinner on the engine and tightened up the prop nut, the shaft would not turn at all. Now I did not tighten it anywhere near tight enough to fly with but tight enough to spin the prop over. I removed the spinner and tried with just the prop alone, and I had the same issue. I then removed the drive hub and woodruff key and I could feel from experience that the shaft by itself was turning fine. I replaced the woodruff key and drive hub and the shaft still turns fine. Then I replaced the prop again with the washer and prop nut and slightly tightened it down, and now it wont turn. I only tightened it slightly out of fear of doing any damage to the bearings or whatever. However I could not turn the prop clockwise and when I tried to go counter-clockwise, all I did was spin the prop nut loose. What is the problem with this engine? The woodruff key I ordered from Tower Hobbies was - (Your # OSMG9360) which is in their parts list, listed number as number - 29008219. Please explain I need help as to what is going on. I have had a lot of engines in the past and have never experienced any issue like this.

Thanks a bunch

Ed

Oilsands

Would you have a picture of it? It may help others to see the problem you may be having.

Electriceddie

Hello,

I dont think a picture will help. The woodruff key and the bearing fit together fine and turn fine on the shaft. Now put the prop on it and it wont turn. Not sure what to take a picture of or if that would help?


Ed

Ace9

Electriceddie; I don't know if this helps, but make sure that there is a thrust washer located directly behind the drive washer (hub) after you slide it off the crankshaft. Here is a link to the part I'm referring to. http://www3.towerhobbies.com/cgi-bin...?&I=LXCW52&P=Z

Oilsands

A per the above reply, that is what I was thinking of and what it sounds like (that you are missing a spacer or thrust washer). This is causing the spinner plate or propeller to come into contact with the engine case when you tighten the bolt.

Bax

My Feedback: (11)

Very likely, you are missing the thrust washer, which goes onto the prop shaft first. Then you install the woodruff key and drive washer. The thrust washer rides upon the front bearing's inner race, and the drive washer rides upon it. Without the thrust washer, the drive washer will move back as a prop is tightened and touch the case. That prevents it from turning.

Here's the part you need:

OSMG9136 46120000 THRUST WSHR FT120-160 US$2.29