Thorp Air Command - T18.net

So....anyone here have any experience with this little gem?

http://balancemasters.com/ultralights/experimental.html

The logic seems sound - he is adverting it werkin on Lycomings. The 0-360 in my last plane ran really smooth at virtually all RPMs - the 0-320 I have now (with C/S prop) does so only in some realms of the green RPM spectrum - runs smooth at 2550-2700 and 22-23500 - in between it gets a little vibratory. Nothing major, and I've noticed it helps if I take my time dialing the prop down.

I'm tempted to try it out.....

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

Funny...and you can be funny at times ! I was just looking at this HooDeeDo the other nite ! I have not seen it on the Vans sites or any other sites ? I think we need an Engineer to weigh in here and help us evaluate this spinning disc of death ! Would hate to have the EPA on my rear when the Mercury hits the ground and kills the Northern Calif. Pup Fish ! More than a BIG BOOM !

RB

I paid a guy $100 to dynamically balance Homeys airplane. Made a huge difference.

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Lee Walton
Houston, TX
N51863,N118LW
KEFD

Maybe the bottom line is how much will this "Wheel of Fortune" "balance" a prop/engine ?" How far out of balance is too much for it to work ? Maybe Judge Judy has the answer ?

RB

Sounds about the same as the Landoll harmonic dampener that has been around for a long time.

viewtopic.php?f=48&t=7094

Bernie Fried
N18XS

I would recommend getting a dynamic balance job also, for a fraction of the price. I have a dynamic balancer, & here's what I see when balancing a prop that has a Landoll dampener - I still see imbalance almost always. Additionally, even after dynamic balancing, when re-checking there seems to be some out of balance condition for a short period of time after restart, regardless of what is claimed about the unit stabilizing in a balanced condition. In my opinion, this is extra wear & tear for a few seconds at least every time you start the engine after it's been sitting for awhile. I don't know how this particular unit works, but it seems like a similar principal.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Does all this JIB JAB pertain to wood or metal props ? Seems like the wood props would have more of a concern due to moisture content , "shrinkage" and a slight of hand to "warp ?" I don't know just asking the Holiday Inn Express Question ? >:(

RB

It pertains to both wood & metal. Wood is, of course, subject to change with time, but I have seen little to none with my own Aymar/Demuth over the years. I live in a dry climate, but a properly finished prop, taken care of can be very stable, balance wise. I've seen very few props, whether metal, wood, constant-speed, whatever, that we're perfectly in balance before dynamically checking them. Often, imbalance also originates from the rest of the rotating assembly - spinner, ring gear, etc. Get your prop assembly dynamically balanced, & you're probably good for a long time, unless you refinish, damage it, or change the spinner.

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Thanks for the info John ! I have not had ANY balance done to my AD prop ? In fact as a jet guy I do not really know what an in balance with a wood or metal prop really feels like ? I'll just have it checked out . It can only improve the situation ? BOOM to SMOOTH ! MY AD prop is well cared for as they no longer make them ! I even have sprayed the Stuarts ceramic coating on the leading edge of the prop to extend it's service life . It seems to help even in light rain . Only "slight" blade erosion/pitting on the super sonic tip !

RB

I did not have this one. I had the Landoll one. When we dynamically balanced my T18, we could not get the ips (balance) down to 3 with the Landoll unit installed. I yanked it and we balanced down to 1.2 as I recall.
Not a fan. I would like to find a steel ring if anyone has one.
Cubes

Have Zero experience with the Landoll harmonic dampener or Fraser's "little Jem" balancer.
However, I have several years experience balancing helicopter main rotor and tail rotors with 2,4 blade set ups and tandum 3 bladed Voyager (Sea Knight).

I recommend the following actions should be carried out prior to buying or getting a propeller balancing performed.
1. Perform a visual inspection of your prop. Does your prop exceed limits by the prop manufacture.
If the prop manufacture is out of business the EAA video series provides some guidance so does FAA Advisory Circular 20-37D
2. Is your prop out of track. Make aircraft safe and measure from a fixed point on your aircraft to the blade rotate and perform same for all blades should be within 1/16 inch measurements.
3. Inspect your spinner and backing plates for cracks missing hardware.
4. Inspect prop bolts for correct torque.

My EAA chapter in Ottawa Canada (245) uses a prop balancer similar to Aces Pro balancer http://www.probalancersport.com/ (prop balancing for members). This type of balancer dynamically balances a prop and obtains balance by adding weight (nuts washers and bolts) to either the starter ring or the spinner / backing plates.
Personnel experience has shown me that a statically un-balance prop can be fine tuned balanced using the dynamically balanced procedure. Note a statically balanced prop will usually require less work to get it to acceptable IPS readings but can be satisfactory done without. (impulses per second) (measurement scale of imbalance)
If you have a prop that has had a static balance weights added do not remove these weights. http://www.acessystems.com/downloads/manual-gpb/gpb.pdf further details info on dynamic balancing.
We have had success balancing in winds under 20 MPH, away from buildings and directly into the prevailing wind.
Here is a short video showing how simple the process is: http://www.youtube.com/watch?v=RyNIPsF-7Jg
The computer gives a clock angle, the tech determines the clock angle with the plate on the spinner and adds computer predicted required weights, usually a couple of runs can lower your vibration to .05 IPS or less imbalance).
One point to raise if you have a mechanical issue with your engine, out of round crank shaft, loose cylinder, engine mount etc prop balancing will not resolve these balance issues.

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Victor J Thompson
C-GIRQ
In memory of Dad

Lots of good advice, Victor. I don't mean to nit-pick, but you're actually measuring the level of vibration, not the rate... IPS stands for "inches per second", not "impulses".

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Thanks John read my submission over a couple times, your correct inches vs. impulse didn't catch the error.

Must have been distracted by a hockey game today,...

Our EAA chapter loves the little balancing rig.

We use this tool and others as a full Chapter membership benefits.

Even the old timers who experience lowered vibration levels in their birds speak more positive about the "new technology".

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Victor J Thompson
C-GIRQ
In memory of Dad

Since we're gettin persnickity pickity, I kinda figgered vibration was measured in units of acceleration. (As in....something is trying to "accelerate/increase" an out of round/imbalanced condition that is being held back or in place only by, for lack of better terms "mass and rigidity"). Acceleration is not just velocity, but an increasing velocity and hence is measured in inches per second per second. (inches per second squared)

Maybe I ain't thinkin right.....You injunears can speak up now ifya like.....

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

Since you asked, Fraser, vibration can be measured in several ways. What we're doing here is measuring vibration amplitude, and using an accelerometer to measure movement with velocity in inches per second PEAK (IPS for short). I didn't mean to get into all the terminology, but just wanted to make the point that we were measuring an event, not the number of events.
If that doesn't confuse you, then you're un-confusable. Huh?

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John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE