Aerial Madness

I need to install a 20x10 prop (I chose the 3W) on my Moki 2.1. My fabulous Tru-Turn spinner uses a hefty adaptor. The adaptor actually fits through the prop. Therefore, I need to enlarge the hole on the prop from what looks like 1/4 inch to just over 1/2 inch.

I'm getting kind of anal these days concerning precision (as compared to the good ole redneck days of "hold my beer and watch this) and would like you guys to comment on how you drill out props while maintaining true center. My experience has shown the center line to "drift" some when opening up hole sizes.

I appreciate your comments.

Aerial Madness
From the Hills of Tennessee

FlyinHigh

Well, I've never done it with a prop, but the theory with keeping on center would be to step up in increments with different size reamers. If you have a quarter inch hole to begin with, buy a 3/8ths reamer with a .250 pilot. The pilot tip guides the rest of the reamer through the hole. Depending on how large your eventual hole size will be over the original, you may have to "step up" with two or three different reamers.

Otherwise, as you suggest, just opening up a given hole size with the eventual size drill will stretch and perhaps oblong the hole. (Here.... hold my beer and I'll show ya.)

RaceCity

Throw the prop on the bench and work on the beer.


"24hours in a Day...24 beers in a case.....Coincidence?"

-Steve Wright

w8ye

My Feedback: (16)

Twist drills are bad about not drilling to size, roundness, or on center. It would be best to use a reamer.

However, in the hills, you don't always have access to reamers. If you have a drill press, align the prop under the center of the chuck with the smaller bit. CLAMP the prop down and then go through the succession of increasing drill sizes until you achieve your desired size.

Enjoy,

Jim

Hobbsy

My Feedback: (102)

You can also get a drill bit from B&B that has 1/4 in. pilot but a drill press is a must.

FlyingPilgrim

My Feedback: (26)

Take hobbsy's suggestion. Spend the $12.99 and invest in a stepped drill from B&B. It is a must have for the Tru-Turn adapters.

scalebldr

My Feedback: (7)

i have always used a step reammer that fox sells someone should be making this available in the larger sizes these days.

Aerial Madness

Thanks guys for these tips. I'll look for a reamer large enough to do larger props. I've always used them for the smaller ones.

I went ahead and used my drill press last night with a drill vise to hold the prop perpendicular. I had purchased a new drill bit (boy these dudes are expensive) and it was very sharp. Once I had the prop centered under the chuck, I made the hole (17/32") to be exact. The TrueTurn adaptor is 13.3 mm, so I was real close. From the looks of it, the hold is still in the center.

I'm not totally satisfied with this method, I think reaming would be better.

At least I can now test run the Moki 2.1 on the Fourth of July ! Let the fireworks begin.

BillHarris

> From the looks of it, the hold is still in the center.

You're still approximate on the centering of the drilled hole. You can't eyeball to within .004" (half your clearance).

The best thing to use a prop drill with a pilot.

B&B Specialties stocks a 13.4mm drill:

http://www.bennettbuilt.com/page9.htm

hilleyja

My Feedback: (3)

Fox does have a step reamer for this size.

Tower Hobbies: Fox Step Prop Reamer Metric 10 & 12mm for $14.69.

http://www2.towerhobbies.com/cgi-bin...?&I=LXNL18&P=7

If you have the TRU-Turn adapter that fits inside of the prop then you want to ream the entire dept of the prop to 12mm.

If, like me, you have the standard adapter for the Moki (I have the 180 -- same size as 2.1) then you need to be a little more creative.

1) Ream the Tru-Turn Spinner backplate to 12mm
2) Ream the entire dept of the prop to 10mm
3) From the back, ream 1/2 of prop dept to 12mm

Both the Moki 180 and 210 have 12mm prop shafts. The threaded part of the shaft is 10mm and the unthreaded part of the shaft is 12mm. Why they did this I do not know. The dept of the shaft that is 12mm is slightly more than the thickness of the spinner backplate and therefore requires the prop to be partiall reamed to 12mm.

ajcoholic

My Feedback: (10)

One thing I find that works extremely well, is the stepped "unibit" drills that are carried at better hardware stores and most if not all machine tool supply houses.

They have a number of different diameter steps (allthough the steps are only about 1/4" long, they are used only to start the hole for the second bit which you drill straight through) and are really designed to drill sheet metal... BUT do a wonderfull job of enlarging holes in wood and composite materials.

I drill down to the step size I need, then switch over to a wood twist drill which is them guided by the proper hole size allready in the prop.

Done on a drill press your hole gets in the exact centre each time.

Due to the nature of the cutting edge, the unibits do not wander, chatter or go off centre, much like a reamer they "scrape" rather than dig in.

AJC

hilleyja

My Feedback: (3)

Actually, if you look closely at them they are designed exactly like reamers.

w8ye

My Feedback: (16)

You would be very fortunate if the original hole was within .004" of true center. Most props are notorious for having the hole off center a little. The Windsor prop balancer is actually a device to locate a new center hole for the prop that will balance it.

Be sure to rebalance the prop when your done.

Enjoy,

Jim

scalebldr

My Feedback: (7)

what about props that have the hole not perpendicular to the back of the prop.this was a problem in the past with wood props as the blade tracking was off and on larger props a 5 bolt adapter was used to keep the blades tracked properly and i even ended up buying a tool from rhom that would square the prop hub to the drilled hole.

Aerial Madness

Guys,

I spent my Independence Day breaking in the fabulous Moki 2.1. I mounted it to a test stand. I ran a gallon through it (Omega 5%).

Anyway, the props that I drilled, simply by using my drill press did not seem to have abnormal vibration. I ran the Menz 20x7 for break-in, and once I got the engine on the plane, I ran a 3W 20x10. Wow what a prop. The vibration was abnormally LOW. I was astonished. I was only able to taxi it around the yard some (my honeydue list was too large !).

The test flight will be Friday this week.

Thanks for all the discussions on prop reaming.