Sometimes I think I'm a liittle strange or something. I asked this question on the Scale Aerobatics
board but didn't get a single reply? Either I am not part of their loop, or it's a useless question.
Oh well, you guys will tell the story Here goes;

Whenever I mount a new, or remount an old prop, I check to see if it runs in
the same "plane" so to speak with an unsophisticated gizmo I keep in the
van. In other words I measure the difference in position for each blade on the
same side of the plane.

Does anyone else do this, and what do you do if it isn't true?
I just mounted a spank brand new wooden prop on a 150cc and it's less than
I'd hoped for )-:

I messed with it a bit and got it pretty good, but was wondering what you
guys settle for, if anything less than perfect?
What are the cons of a prop that runs a little out of "plane"
I torque my wooden props to 37.5 inch pounds, and cf to 40.
Thanks and take care_bob

Man, you got more time and patience than I do. I balance the prop, bolt the prop on the engine, don't use anything but a wrench, flip it over and fly. Don't care what plane it runs in. What difference does it make.
Just curious, what do you do if it's not in the same plane. How do you check it with the engine at full throttle under load,(where I would think it matters),Please don't tell me you move the tool until it hits the prop. Sounds like something a total perfectionist would do, and if that's the case you don't get to fly any do you. Cause there ain't no perfect plane out there.
You asked , you got.

If this is the result of the blades having varying amounts of stiffness and knowing that prop loads are not linear, they are going flex different amounts at different rpm. You would end up chasing your tail towards the end of the rainbow. If it is the result of the back of prop hub not being flat in the same plane as the blade tips, you could come close to getting it right with a little careful sanding on the rear of the prop hub. I'm sure others are more "experter" than I am on this though.

I went through the tracking thing on my first gassers -
tracking was awful-
So - I tried different spinner setups .
On single bolt engines, a crowned knurled spinner backplate grips well- but can cause a slight prop mis alignment.

On a multi bolt engines and a raised knurled backplate - the clamping pattern can really misalign tracking.
I have multi bolt an almost all my gassers (cept for the 35 Roto), so I now use only flat spinner backplates .
this pulls the prop flat to the backplate .
If the prop was drilled on a true drill setup , runnout should be zero -OR at least as good as it was from the mfgr.
Some props have grain differences from blade to blade which cause runout under load -
We use these for spatulas.

I'm not trying to be anal or anything. Those who fly 100cc and larger engines know what vibrations are present and the havoc they reak on our airframes and equipment.
I didn't mention that this is a static test only. No, I do not check at full throttle, or any RPM for that matter. It just made sense to me to start out as best as possible. Like I said, maybe I'm a bit strange

It probably would shake like crazy if it were out far enough. Before I took the time to check, this particular set up had a 5/16" difference from one side to the other.

Thanks Dick!

If the hub surface is not perpendicular to the crank the prop, any prop, will not track perfectly..All the engines I work on get checked with a dial indicator...All engines get set up vertically in my mill and have the hub resurfaced, that way if the prop is good there can be no runout...A small misalignment at the hub gets pretty big when measured 12 or more inches away at the tip of the blade..

Sounds like a good practice to me.
My engine has a good hub. Different props give different results at times. Most can be adjusted through the 6 hub bolts.
Thanks for the reply_bob

It is a normal procedure to track the wooden propeller on full scale airplanes. You start with the spark plugs removed and the bolts torqued to about 20% of the final torque, compare each blade by rotating to a stationary object and then tighten the appropriate bolts until the final torque is reached and the blades are in track, you should be able to get the blades within 1/16 inch track on a 72 inch propeller. The bolts should be checked for proper torque after the first flight then about every 25 hours.

Thanks! I knew I wasn't totally crazy[X(]

Take prop out of box, balance prop, stare at prop, bolt prop on, stare at once again, smile, and fly,, Hey Bob that is a common practice and a good idea but I do not have the patience,,[:'(]

Slow and steady wins the race...

that is true

Making some of the 6 bolts on a prop hub tighter than others is a very bad idea...[sm=thumbdown.gif]

It's not so much that some are tighter, but it's more in the sequence to get the track right.
Like I referred to in the original post, wood are 37.5 inch pounds, and cf are 40 inch pounds.

I noticed when I ran my 'BME' engine with a 'BME' 26x10 prop last fall it had about 1/4 inch difference between the blades tips. I haven't measured the difference when the engine is off. I don't want to induce any more vibration then I have to, but would this be considered normal?

I have limited heli experience, but there is a lot to learn by setting one up.

if you read the setup procedure for a helicopter, you will understand everything you need to know here, and more. just a few of the things I remember were:

each blade has the same mass--this will be close enough by static balance for a fixed pitch propeller,
each blade has the same mass moment of inertia about the spin axis--don't worry about this--it will be close enough as manufactured
each blade has the same mass moment of inertia about the longitudinal axis, and the axes of each blade coincide.--should be ok for propeller "as manufactured"
rebalance the assembly statically by adding weights in a manner that maintians the relationships established above,
run the thing after estimating the pitch angles, and fine tune pitch one side versus the other until "tracking true"--
At this point, you should be close for dynamic balance and thrust balance. fine tune the dynamic balance with small weights on the flybar. this is trial and error (unless you are really swamped with free time and have built a dynamic balanc machine)
Fix a propeller by shaving the blades to correct tracking AFTER it is mounted true to the spin axis. maintain static balance by removing material from the front of one blade and the back of the other. maintain the shape, and work on the tips primarily because you won't have much success reshaping-for-thrust in the middle areas.
This should only be necessary on very large or very badly tracking propellers. I would not accept anything over 1/4" (1/8 for small props). Nor would I concern myself with anything less.

Safety: if you don't fee comfortable with the amount of material you are removing, toss the prop. if you are viewing the tips to verify track, use a clear safety shield and test at various speeds and through acceleration/deceleration. if the disc oscillates wildly (like the old nylon props for small models), consider tossing it. When, not if, it scatters, it is a mess.

ms

I had never even thought of measuring this before. I checked my G23 with APC 17 x 6 prop, and my G62 with a Mejzlic 22 x 10. The APC was dead on the best I could measure it from the horizontal stab, and the Mejzlic was 1/16" off measured the same way.

Nogyro -> Tell me how you do the test with the stab? I use a pointer placed just at the end and at the rear of the prop on one side of the plane. I then pull the prop carefully through one revolution and note any differences_bob

bob_nj, This is very low tech, but I did it on both sides of the fuse and came up with the same difference each time. I turned the prop horizontal, stuck the end of a tape measure in the inside corner where the horizontal stab meets the fuse, and measured to the tip of the prop. Rotate the prop 180 degrees and measure the other tip. Worked for me.

Got It