Dynamic balancing of small Continentals

[Robert Lees]

Thanks Tim for the info. I figured you would know. Besides TCDS data how else can an installer confirm power output? Are dyno results acceptable documentation? It would seem that with choices of engine age, tachometer accuracy, exhaust, intake, prop, and mag timing the actual power could be all over the acceptable range.

I probably will have my engine/prop balanced at some point. I've done that on a few other planes and it can make a difference in smoothness. It's ok now but I'd still like to know the IPS data in case it changes over time.

Gary

I'm also interested in dynamic balancing for the small Continentals. I've done it on large prop/engine combos with large diameter spinner backplates (to which you can add washers to balance the imbalance) but, with a small skull-cap spinner, and a small radius to work with, is there a way of effectively dynamic balancing a small Continental?

Rob
[edit for continuity: PA1195's post arose from this thread about Terry Bowden
Rob]

[PA1195]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

I'm also interested in dynamic balancing for the small Continentals. I've done it on large prop/engine combos with large diameter spinner backplates (to which you can add washers to balance the imbalance) but, with a small skull-cap spinner, and a small radius to work with, is there a way of effectively dynamic balancing a small Continental?

Rob

I believe (haven't done it yet with mine) that within limits weight can be added to the propeller's attaching hardware. Longer bolt(s) or washers could be used. It would depend on the level of initial imbalance and allowable changes to the attaching hardware.

I would first run the engine in a static mode to determine the level of imbalance. If desired, rotate 180* or re-index the prop providing the manufacturers haven't specified a prop position the crankshaft flange and retest to see if it changes the measuring instrument's data (any thoughts on this?).

The equipment I witnessed on other planes were Chadwick-Helmuth systems (http://www.dsi-hums.com). Weights (hardware and washers) were attached either to the spinner or bulkhead. I'm sure there's other systems now available, and my mechanic has a source in Fairbanks he recommends (mainly for Pipers with larger spinners). FWIW I just e-mailed him for his take on balancing my prop and will know more soon.

I see no reason why not try it with the T-Craft?

Gary

[PA1195]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

My mechanic replied yes let's do it when we put it on floats (soon). So I'll take notes, pics, and try to reply if and when it happens. Visibility in Interior Alaska is IFR/MVFR in forest fire smoke so It may be a few days until I can aviate to move the plane.

Gary

[astjp2]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

I use an Aces 1000 balancer. It needs a new photo transducer which is insanely expensive for what it is and feels like witchcraft sometimes doing a balance. I have done only 6 airplanes with it and spent $3700 for it. Not a money maker at all. The manufacturer also charges $700 to calibrate it every other year. Some day I will get to balance mine when I get the balancer calibrated.

I remember in 2005, the smoke was so bad in Fairbanks that there was only a half mile visibility for 3 months. The fires near Tok were real bad. Not much flying that summer. Tim

[PA1195]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

Prop and engine balance was done today by a local Certified Repair Station. Vibrex-Chadwick Helmuth unit with analyzer. An accelerometer gizmo attaches to existing bolt on top of forward crankcase and is wired to analyzer. A reflector stuck to rear of one prop blade is then read by flashing light taped to top of cowl facing reflector to determine clock position of any engine jump and rpm. The light flash is controlled by analyzer and accelerometer's movement.

Engine was run until warm then at static cruise rpm...2300 in my case was chosen as my tach reads about 50 rpm low according to the Vibrex and I want to cruise 2300-2400. Accelerometer reads vertical movement of the engine in inches per second and rpm versus tach rpm. The analyzer then determines a clock position to add a suggested weight to the prop assembly. Mine required about 40g at 10 o'clock relative to the marked blade. Weights are attached to prop as required for security and will be periodically monitored of course for continued airworthiness.

Initially my recently overhauled Sen M76AK-2-40 was moving 0.4 IPS, which the tech noted was normal for imbalance in his experience. Some get over 0.6 initially. It never felt that rough to me but...?
A couple of runs later with weight added resulted in 0.1 IPS which is good. I could first feel the reduced vibration difference in the foot pedals after the initial added weight, and the metal cover over the main tank and attached GPS mount now remain still from idle to 2300.

It's a worthwhile procedure and I feel has the potential for reduced wear due to lower vibration. I assume if the prop weight is ever changed through leading edge maintenance the balance will have to be reexamined. Not a bad idea actually, as the engine and prop mature together it's cost effective to have it checked.

Gary

[Robert Lees]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

Thanks Gary. Where are the weights attached?

Rob

[PA1195]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

Thanks Gary. Where are the weights attached?

Rob

To the arch brace for the typical small prop cap...large area washers held with AN3 bolt, washer, and nut. They could have gone under an existing bolt head, perhaps using a longer prop bolt, but it was determined for now to place them perpendicular to the prop face between the dome brace and the inside of that prop bolt head that fastened the brace to the prop. Sorta' locks the hardware in against metal to prevent movement. Periodic inspection will be conducted to maintain its continued airworthiness. I'll threadlock the spinner screw today.

Now if I were interested in a change, I'd consider an Ercoupe spinner if it'd fit. Then there'd be plenty of metal to pick a place for the additional hardware, and a larger radius to reduce the required overall weight for the same balance moment. Purists may disdain the look, but for me it may be an interesting mod that may improve cooling and airspeed.

Gary

[PA1195]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

I use an Aces 1000 balancer. It needs a new photo transducer which is insanely expensive for what it is and feels like witchcraft sometimes doing a balance. I have done only 6 airplanes with it and spent $3700 for it. Not a money maker at all. The manufacturer also charges $700 to calibrate it every other year. Some day I will get to balance mine when I get the balancer calibrated.

I remember in 2005, the smoke was so bad in Fairbanks that there was only a half mile visibility for 3 months. The fires near Tok were real bad. Not much flying that summer. Tim

It is witchcraft and the equipment is expensive. I offered to pick up a cable off the ground at the finish and was told to not touch the $1700 cable with MS***** ends. I do Ham radio and there's potentially nothing magical about wires and connections unless the vendor is the sole source...balanced current and controlled impedance costs extra I suppose.

Yes unless the volume were steady or a fleet was being maintained (like a Gov't or commercial contract) it'd be hard to recover the investment. Perhaps it's a way for some to help others and interact at the airport.

Our Alaskan smoke has been bad...even reaching hazardous conditions (full scale right: http://co.fairbanks.ak.us/airquality/). Look at the real time air quality map for a webcam pic of Fairbanks looking south if interested (click on the upper camera). The airport is at the upper right. Check out the Sun angle in late December...3* over the horizon.

Gary

[M Towsley]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

Last weekend was really hazy around here, our weatherman blamed the Alaskan smoke. I don't think that was it but you can keep it up north if you like.

Also, if you put that ugly Ercoupe spinner on wouldn't you have to re-balance again?

[PA1195]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

Last weekend was really hazy around here, our weatherman blamed the Alaskan smoke. I don't think that was it but you can keep it up north if you like.

Also, if you put that ugly Ercoupe spinner on wouldn't you have to re-balance again?

Lots of fires in Canada too...but the smoke can travel distances. Your upper jetstream flow comes from our direction.

Ugly? Ercoupes are beautiful and Fred Weick did a great job in designing a safe airplane. The spinner may not fit the Taylorcraft cowl. And yes, if anything changes in the engine/prop/spinner a rebalance is required. Same for prop maintenance if metal, or potential moisture ingress if wood. I'd like to have a Catto prop if they ever certify them.

For my $ anything I can do to reduce metal fatigue and component wear is valuable. Given the cost of maintaining old metal the balancing is a minor financial concern.

On one plane years ago (a C-185) we flew the instrumented prop through several power, airspeed, and ranges of load. The vibration level and clock node of the two-blade constant speed varied. We had to pick one power (MP/RPM) setting as a balance point. It helped to reduce vibration but ultimately a new motor mount solved the problem.

It may be worthwhile to periodically inspect and replace the rubber engine mount isolators on the Taylorcraft, as well as looking for any interference between the engine and cowling.

Gary

[M Towsley]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

You misunderstood. I called the spinner ugly, not the airplane. Lol

[PA1195]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

You misunderstood. I called the spinner ugly, not the airplane. Lol

Yes I misread your comment...apologies.

I wonder how much paperwork it would generate to approve an Ercoupe spinner on the Taylorcraft? How many dives to redline and climb at best rate for who knows how long, all the time recording engine parameters with digital sensors to later download and submit to engineering? Maybe it's not that complicated in reality. If so I may do it this winter just to fly faster and cool better.

Gary

[astjp2]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

I have an ercoupe spinner installed, maybe someday I will do some paperwork. Tim

[PA1195]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

I have an ercoupe spinner installed, maybe someday I will do some paperwork. Tim

The pics look good Tim. Not at all ugly and very functional. Lots of room for balance weights if desired. The Caribou cowl ornament finishes off the Alaska look nicely...just aim between the antlers and you'll never get lost. They just know the way.

PS: I have your seatbelt anchor system in my plane and it saves lots of room.

Edit: the T that I had 41 yrs ago had some of Bill Diehl's Arctic Tern mods...squared wing tips, ailerons, and cowl (N29694). It's still around somewhere. It was a 38 mph airplane. If you could get to that speed it'd fly on floats. It landed at that as well.



Gary

[Robert Lees]

Re: Terry Bowden still in busness ? or has the rain closed him down ?

To the arch brace for the typical small prop cap...large area washers held with AN3 bolt, washer, and nut. They could have gone under an existing bolt head, perhaps using a longer prop bolt, but it was determined for now to place them perpendicular to the prop face between the dome brace and the inside of that prop bolt head that fastened the brace to the prop. Sorta' locks the hardware in against metal to prevent movement. Periodic inspection will be conducted to maintain its continued airworthiness. I'll threadlock the spinner screw today..

Gary

Gary. I'm not sure I quite understand. Are the weights attached to the skullcap spinner attach bracket? If so, there are only two orientations to fit them. What happens if those orientations do not coincide with the bracket?

Sorry to be a pain, but if you have some pics of where the weights attach, that would help.

As an aside, I don't like the Ercoupe spinner; it's not original to the Taylorcraft and looks ugly, in my personal opinion.