Need help with prop tracking...
 

<div style="text-align: left; ">Hey guys,
I've been into nitro for about a year now. I have an OS FL70 and a Saito FA62A both in very good condition, no crashes. The FL70 has been on an airplane for over 60 flights so far, and the FA62A has been run 3 times on a bench. As I was setting up my Saito, I decided to check blade tracking by putting my airplane on a stand with a solid point on the ground (an oil can) and I rotated the propeller to see if the distances were correct. The tracking was 1/8" off (by the way this is with a 13X6 APC, brand new). Because of this, I tried another 13X6, also brand new, and this time mounted it with the stock prop bolts that came with the engine, only to get a similar tracking.
I then looked at my FL70 for comparison. This one has already flown over 60 flights, and uses an APC 12X7. Upon looking at the tracking, same method, it was a whole quarter inch off!</div><div style="text-align: left; ">I had noticed that plane shakes like crazy, but figured it was the 4 stroke...
Just for one more comparison, I looked at the propeller on an electric of mine, which is a 14X7 mounted with a nitro prop nut on its adaptor. This plane has hundreds of flights on it. It also had 1/8" difference between each blade. I had noticed even that plane shook like crazy but thought nothing of it.

Clearly, something is really going on here. Every propeller is APC, and properly balanced. They are all attached using hardware from Tru Turn and OS. I always ream to the correct size, using a standard reamer.
Is there a way to adjust the tracking? I have no clue what I've been doing wrong all this time...
Please help, for now I'm groundng all my airplanes until I figure out what's up.

Thanks in advance
Mike</div>

RE: Need help with prop tracking...
 

Get rid of the spinners and mount a prop on the engine hub. That will rule out or in the accessories.

RE: Need help with prop tracking...
 

Thumbskull, that's a good idea. I did that with my Saito just now, still 1/8" tracking issue. I'll go try it out with my FL70, I'll get back to you.

Mike<br type="_moz" />

RE: Need help with prop tracking...
 

You need to use something ridged and straight like a metal ruler in place of the prop. Mark the back plate so you have a reference, and make sure bearing play is not skewing accuracy.

RE: Need help with prop tracking...
 

The FL70 improved by 1/8" after taking off the spinner, but the tracking is still 1/8" off :/

RE: Need help with prop tracking...
 

I'd lay the props on a bearing or something true while it sits on a flat table and measure the tips to the surface.
That will check the props tracking.

RE: Need help with prop tracking...
 

Bad tracking is caused by either the engines drive washer or the flat of the rear of the prop hub. Not usually the drive washer. I have had to sand the back of some prop hubs to get the tracking right. Biggest trick is keeping the surface flat as you remove the side which brings the tracking back on line.

Another thing. When I check tracking I always make sure the plane is firmly secured so it does not move at all when turning the prop. Also, I remove the glow plug to make turning the prop easier.

One problem I found with the nylon props is if you have a prop strike it will sometimes bend a blade, and it will stay that way.

Just for the sake of experimentation, when checking one of your props that shows being off, bend one of the blades forward or backward and see if that doesn't correct the tracking. If it does. check it again the next day to see if it stays that way.

In my opinion tracking can cause vibration, but I don't believe it is as critical as balance.

Just my two cents

RE: Need help with prop tracking...
 

Tacx, actually I have had a lot of prop strikes with the FL70, come to think of it, at least once every time I go to the field... (short gear, bumpy grass runway. I've been thinking of going to an 11" 3 blade to add clearance). I put my spare, never-run propeller on, without the back plate (stock plastic spinner), and saw that it was about 1/16" tracking difference; I think that's acceptable, but what do you think? I then put the backplate back on along with the new propeller and the tracking was back to about 1/8"...
As far as the Saito, I realized that I've been using the wrong reamer (7mm crankshaft, and I've been using the standard reamer. I am such an idiot sometimes...) so I'll have to buy a metric reamer and try again. I'll get back to you all on that.

So again, is 1/16" difference bad for the FL70? If I go ahead and get another Tru Turn spinner, it may stay that way. I need a spinner; I use an electric starter and I like my fingers too much to hand start.
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RE: Need help with prop tracking...
 

Don't use an APC to check the prop tracking they are notorious for having the hole drilled crooked through them.

RE: Need help with prop tracking...
 

Ditto...............use a pice of al bar stock that you know is true.
a piece of 3/4 x 3/4 al angle stock is perfect for this.

the APC will have you chasin demons all day long.

RE: Need help with prop tracking...
 

Should I not use APC on my airplanes then? The only reason I'm checking prop tracking is to get a smoother running plane without all the massive vibrations that I've been experiencing. I have no doubt that my drive washers and crankshafts are straight; these engines have not been crashed and the Saito has only been run twice on the bench; otherwise factory new. Should I switch to a different propeller and try again?

Thanks for the replies
Mike
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RE: Need help with prop tracking...
 

I chucked my stepped reamer along time ago. Now I use nothing but a tapered reamer. First, you don't have to worry about having a SAE and a Metric on hand. Second, When the stepped reamer gets dull you cant' sharpen it without changing the diameter of the steps. With my tapered reamer I have sharpened it several times, and it doesn't change it's usefulness.

When I ream my props with the tapered reamer I go from front to back. I ream to the point to where the rear of the hub fits snug on the crankshaft. With the front of the hub ever so slightly larger than the rear it allows the back of the props hub to fit flat against the thrust washer but still keeps the prop centered on the crankshaft.

As Hobbsy says, A prop with a severely crooked hole is going to throw everything off. The crooked hole is trying to keep the hub crooked and the prop nut is trying to press the hub flat against the washer. This causes stresses on the prop, thrust washer, and prop blades which can cause bad tracking.

That's why I like to use my tapered reamer. It eliminates the fight between the crooked hole and the drive washer/crankshaft.

As for how far off I am with the tracking, it somewhat depends on how big the prop is. I have props from 11 to 18 inches. If I get them to 1/16 th I'm happy.

RE: Need help with prop tracking...
 

Tacx, that's actually a really bright idea... I never thought of it that way before. Everything stays square then. I think I may try out the tapered reamer before I go and get another step reamer.
After trying this, do you know of any way to adjust the tracking? Sanding the hub seems a little sketchy... I'd be afraid to take off too much or too little...

Thanks a lot of the tip!<br type="_moz" />

RE: Need help with prop tracking...
 

are you serious?..................it's not the hole even though that is the obvious suspect.
you need to make sure the back of the prop hub is true first. any prop can be off, and you need to learn how to check that first........but still, using a prop to check for tracking is pointless whether it's reamed out correctly or not.............when you tighten a prop down it has no choice but to sit flat on the drive washer does it not?...........

RE: Need help with prop tracking...
 

Sorry, I'm still a real novice at this. Can't avoid sounding dumb every now and then.
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RE: Need help with prop tracking...
 

Just came across this thread...... Have I been doing something wrong ?

I've been flying for some 22 years now, and not once bothered to check for the "tracking" of a prop, although I do spend alot of time balancing each and every prop that comes in before it goes on the plane.

So how critical is this ????? I fly only sport-for fun only, no competition. I do want the most out of my planes and equipment though. Guess I'll go home and track all my propellers now. Great googly-gock !!! Something more to worry about !!

OK So now I want a tapered prop reamer. Cannot find one listed-Only step reamers. Where can I get one ?

RE: Need help with prop tracking...
 

Mustangman, I'm no expert, but I do know that incorrect tracking can cause more vibrations in flight than normal and also can cut down engine performance. Tracking is pretty important to competition pilots, but for me personally I just want a smooth running airplane for my sport flying.
Do a quick Google search and you will probably find a few different online hardware sites that sell them.

Mike<br type="_moz" />

RE: Need help with prop tracking...
 

Thanks Mike:

I think we're on the same page here. Something can be gained by having a properly tracking prop. but don't want to lose sleep over this. When I go home tonight, after school, I'll check several engines.

Cary

RE: Need help with prop tracking...
 

A tapered reamer made for tubing works as well as the ones sold specifically for RC. I paid $4 for mine and it works great.
An out of track prop is going to cause some circular vibrations which will mostly stress your engine mount and firewall, but I suppose could show up as tail wiggle. Sanding the hub is the right fix, and it's not hard to do. Lay the sandpaper flat on a table, then apply pressure to the high side of the hub and sand it. Go slow since you don't have to remove much material to make a noticeable difference. If you go too far, just turn it around and sand it the other way.

RE: Need help with prop tracking...
 

i realize this, and you don't sound dumb at all..in fact you are smart to at least show and ask about your methid here.
checking things like you show in your pictures can produce twice the error you really have if you have one at all.
i did a check on my engines in these pics a week ago and have a more precise setup, but since i am running these engines today i used the test mount to setup a way to show you how things really need to be measured............knowing that not everyone has depth micrometers, calipers and more so a dial indicator as is in the pictures to do exacting checks, you can do a very consistent job of checking by mounting the engine in a solid device to eliminate any movement that will give added false readings. then take a straight edge (the bar from a Robart incidence meter will do) and drill a hole in it, mount it like you would the prop.
starting from one side of the compression stroke with a block up against the str. edge, then rotate it thru to get the other side of the edge to line up with the block you just started with. if that shows a difference, then note it, and then loosen and rotate the straight edge 180 * , retighten and check it again. if the St edge is true you should have the same results........if different, then the straight edge is not straight. get another straight edge and try again.

last but not least is to surface the prop hub, and there is an easy method to do it too.......it just hasn't been posted yet.

RE: Need help with prop tracking...
 

Summerwind...
All good info, but you are referring to checking the engine drive washer and shaft. I think we are mostly discussing the prop. If you have a prop that has a rear hub surface that is not perfectly parallel to the prop blades then that prop is not going to track correctly. The only way one can check a prop for tracking is to use a prop. I understand the fact that if the crank or drive washer is out of wack this would cause a tracking problem,but most guys don't have the proper equipment to check the precise measurements of an engines components.

Mustangman,
I wouldn't lose any sleep over tracking. Like I said in my previous post. I believe it makes a difference, BUT not as critical as a balanced prop. I always check for tracking only because I want the system to run as smooth as possible. Do allot of guys check tracking? NO, most guys I talk to have never done it.

Now that you are aware of it check some of your props just to see how far off they are. You may be surprised.

By the way, I bought my tapered reamer at at my LHS. The owner who has been in this hobby for many years suggested it. It's the only thing he uses.

RE: Need help with prop tracking...
 

Here you go http://www.thompson-aero.com/index.p...d=62&Itemid=32 also how are you balancing your props? Simply balancing your prop in the horizontal position is not enough and wont show you if you have a hub thats heavy on one side. You need a good balancer http://hobby.dubro.com/videos/1/tech-tip-videos Check out these videos. Good luck

RE: Need help with prop tracking...
 

Didn't you say you have prop strikes nearly every time? That'll damage your bearing and even your crankshaft more than a crash in the dirt.

RE: Need help with prop tracking...
 

Will do..... Thanks for the good info. This is just something I never realize existed and will check.

RE: Need help with prop tracking...
 

Ditto on the tracking. Props have a slight tendancy to distort while turning anyway. And the aerodynamic characteristics change dramatically from the center to the tip.

I have never seriously considered a tapered prop reamer due to the very large probablity of error. And wearing open the hole. I have two stepped reamers, one standard and one metric. That way my hole is the correct size through the entire hub - and if I screw up I throw it away.