NR prop holes to tight

[avidflyer]

Hi all, I remember someone else mentioning this a year or two ago. I searched the archives and didn't find the post. The holes in the back of the prop were to small for the drive lugs to fit in. I finally got around to mounting this prop on my new Kitfox build, and if I forced the prop onto the drive lugs, I would need a hammer to get the prop off. I could push a drive lug maybe 1/16" into the hole with my thumb. My first NR prop didn't have this issue, I got it maybe 6 months before this one. Anyone remember what the solution was that NR said to do? I'll email them tonight, but sometimes it takes a while before they answer. Thanks, JImChuk

[Shadowrider]

Sounds like you have the spacer on wrong?

[avidflyer]

I'm not sure what you are talking about. What spacer? The hub has two halves, front and back. The back has the larger hole for the center boss, and the approximately 1/2" mounting holes that the drive lugs go into. I didn't have any problem mounting my other NR prop on my first Kitfox 4. I've mounted quite a few props over the last 23 yrs flying and putzing with these planes so I think I'm doing it right. I hung a spare warp drive prop on while I get this sorted out. But thanks for your reply. I've been wrong before :-) JImChuk

[jiott]

Jim, I believe Dustin is talking about the usual 2" or so aluminum spacer that goes between the prop hub and the prop flange. Very common on later models; don't know about earlier.

[avidflyer]

Ok, but I don't have a spacer between the prop hub and the prop shaft face. On a brighter note, I hung a spare warp drive prop on the engine and got it fired up today for the first time. Bit of a milestone. JImChuk

[alexM]

This supports my theory that NR, Luga and Meglin have some common "shared resources". The hub supplied with my Meglin 3 blade is also tight. To be fair, the first time I went to install my Sensenich prop it didn't fit either. I called my engine importer to ask him what to do. He was very opposed to the idea of taking a reamer to the holes, and suggested that because the temperatures in my hangar were below 20F I should try warming everything up.

I did that and got the Sensenich hub on - just barely - with some light tapping using a rubber hammer while making sure everything is going on the lugs perfectly straight. Now that it has been torqued and removed a few times I can get the Sensenich prop on/off. I haven't repeated the process with the Meglin hub yet but I'm looking forward to trying it out after I get my engine running.

[avidflyer]

When I tried to fit the NR prop, it was about 70 degrees F at the most, so I don't think expansion or contraction or expansion should be the issue in my case. I had no issue getting the Warp Drive prop mounted and used the same drive lugs. And really, why should they be super tight, the prop shouldn't walk back and forth on the prop shaft. JImChuk

[avidflyer]

Just a follow up on this post. I ended up machining a set of new drive lugs on my lathe. I milled the part that goes into the prop flange down about .005" less than the area that goes through the prop flange on the engine. These should work just fine I'm sure. The one drive lug in the pictures is an original Rotax one I pulled out and measured. JImChuk