adjustable propellers

[tawadc95]

I read about an adjustable pitch propeller (ground I believe) that is being made for small continental engines.
Can anyone help my memory with the manufacturer name?
Thanks in advance,Chris

[jstall]

Re: adjustable propellers

If you could find a BEECH ROBY propeller they were air adjustable with a screw cable crank assembly that went out to the engine and propeller mechanism. Sure would be a cool deal, but they are very scarce.

JS

[Ed O'Brien]

Re: adjustable propellers

Actually they're building the Beech Roby's again. Now called Tarver Props - see here: http://www.aeromatic.com/sb2000_001.htm

Good luck. If you buy one -- let us know about the perfomance.

With regards; ED OBRIEN

[VictorBravo]

Re: adjustable propellers

I have no experience at all with them, but have heard from experienced old-timers that the Beech/Roby propeller is all gimmick and no performance. I don't know if/what the mechanical problems or risks are, but it sure seems like a lot of monkey motion for little or no gain. The blades do not look very efficient from a modern prop design standpoint to my eye. I'd bet that a modern well designed fixed pitch prop executed in wood/ composite would outperform it on a Taylorcraft. It wouldn't seem to be a winner to give up a metal fixed pitch prop for one.

[jstall]

Re: adjustable propellers

Opinion:

In a/c that don't have a super large takeoff/climb/cruse envelope, and won't hardly overspeed the engine in level flight full throttle, the varible pitch is kinda an over kill except for the initial power up on takeoff and a very
steep i.e. VX climb otherwise the extra weight and complication probably not worth it, thats why they didn't or weren't very popular.

Conversly, in a/c that this envelope is quite wide i.e. 80 mph up to 200
one would almost have to have, a varible pitch or the engine would be way out of its limits, and one couldn't manage the horsepower envelope at all as matched to the airframe performance

I climb my BC-12D at 80 mph indicated and full throttle, that gives about 2200 rpm, keeping it up on the horsepower curve and giveing a nice climb rate, in fact it climbs as good at that setting as it does at 60 in ft/min. and you are going somewhere.

Cruise is 2150 at 95 mph/indicated at 2200 I get 100 mph indicated
all in level flight

JS

[tawadc95]

Re: adjustable propellers

Ed,
aeromatic is the name I am after,a friend wants an adj for his 135 h.p. super cruiser and all he knew of was the old beech prop but I knew I had read somewhere of a new design.
aircraft spruce I saw last night is selling an electric prop.
THanks guys for the quick response!!!!!

[Ragwing nut]

Re: adjustable propellers

Tarver Aeromatics are not cheap. I have flown behind Aeromatics on Bellanca Cruisairs and they are worth their weight in gold, climb and cruise performance. Tarver also owns the Roby TC's as well. I have always wanted to fly behind one but have not had the chance yet. I do have an Aeromatic for a Swift 85hp that I think would be cool on the front of a Clip Wing. Someone on here said they were buying a Tarver prop for their float equipped Taylorcraft.

[tawadc95]

Re: adjustable propellers

4,800 bucks!

[1938BF50]

Re: adjustable propellers

been one on E-Bay for a while now. Item number: 160178921048. There is one on a Taylorcraft on floats in Chet's book.

[Ragwing nut]

Re: adjustable propellers

been one on E-Bay for a while now. Item number: 160178921048. There is one on a Taylorcraft on floats in Chet's book.

The one is Chet's book has a Freedman Burnham on it I am almost positive. Those are very rare and ground adjustable. I have had a couple hubs for those but never an airworthy one.

[Ed O'Brien]

Re: adjustable propellers

Tawadc;
Good luck on the prop. Since you're in Yuba City, CA. and the Beech Roby guys are in Fallon, NV... provided the pass ain't snowed over in 10 ft. of new fluff stuff... it should be an easy trip to go see Tarver. (Not far from Reno)
I'd recommend you take a look see before you buy. It seems that none of us know enough about these adjustable-props for a T-Craft to give you a knowledgeable recommendation one way or the other. If you do a go see, you'll be, either the resident fountain of wisdom, light, and truth, or... the Tibe's village lab rat. At least go give'em a look. Tell us what you find.
With regards;
ED OBRIEN

[tawadc95]

Re: adjustable propellers

Ed,
it won't be for me,I was asking for a friend of mine.
He has a 150h.p. pa12 he wants to put it on for a trip to Alaska in June.
He will be going to visit them next month
May seem like an odd reason but I don't want one on my bird as the blades are rather ugly shaped and out of place on an L2,just me though.
The fella with the pa12 is going with my dad who is flying his pa14,they are going slow and just looking at the ground below themfollowing the pipeline up ,wander Alaska for awhile then take the coastline back to norcal.

[Ed O'Brien]

Re: adjustable propellers

Tawadc95;
Not that I got too deep into the subject... but I'd done a
sketchy analysis built on this reasoning... That for a 65-85HP engined T-Craft... ground adjustable props made no sense. This is because of the weight penalty and initial price of the thing. BUT, when you start talking about a 150HP Cub (in your case)... In my analysis I used a Citabria
(7GCBC) the adjustable prop made "some" sense. BUT -- You'd have to fly it a bunch of hours to get it to pay-off.
It made a lot of sense if you were flying backcountry tight, maybe on floats and needed extra safety margins. BUT, flying mostly to airports -- not sandbars -- or little lakes --
a good match metal blade fixed pitch was fine... atleast for me. Good luck to you and your friend and do let us know what he finds.
WIth regards; ED OBRIEN

[Ragwing nut]

Re: adjustable propellers

Tarver is not making Roby blades at this time unless something has changed in the last few months. What do you want to know about them? I have quite a bit of flight time behind one.

[Pro from Dover]

Re: adjustable propellers

Clarification on adjustable propellers

There are several "older" propellers out there that have been installed on various Continental powered ships such as the Tcraft.

First, the Beech Roby is an adjustable propeller, in that it can be adjusted from the cockpit to a range of pitches. Sort of a poor man's constant speed, but not a constant speed. The Beech Robys utilized laminated wooden propeller blades. Beech Bonanzas utilized a later version that was adjustable through an electric motor. Technically these propellers are orphans.

Second, Aeromatics (or Koppers Aeromatics) are an "automatic" shifting propeller. The propellers shift automatically to either a high or low pitch depending upon load and RPM. These are fabulous propellers. Lots of old wives tales with regard to these propellers mostly proffered by folks that are unfamiliar with their workings. These propellers must be set up properly in order that they shift properly. If they don't shift at the correct setting the aircraft can actually have reduced performance in certain conditions. These propellers fell out of favor due to their blades being of laminated wood constuction and replacements were not available. Tarver bought the Aeromatic propeller assets and is one of the first owners to actually supply new blade assemblies. There are oodles of hubs available (due to blades rotting in the past from being in the weather) so he generally overhauls existing hubs. Yes, $4800 is a lot of money for a propeller. Note: A Hartzell for an E-225 Bonanza was priced at $25K before Hartzell stopped quoting them! I have heard very good reports of Tarvers work and workmanship in addition to delivering on product.

Third, ground adjustable propellers are just that. Optimized for only one setting. Numerous ultralights utilize these types of propellers. Sensenich is building ground adjustable propellers that are used on Rotax 912s. Sensenich will also be producing a series of ground adjustable propellers for the new O-200 powered Cessna 162 Skycatcher. Before you jump up and figure you can bolt one of these babies on, remember that the Skycatcher is being certified to ASTM LSA criteria and not FAA Part 23 basis (Which the Tcraft falls under, actually CAR 3). I have yet to see an airworthy antique flyable ground adjustable propeller being used on a four cylinder Continental. Doesn't mean they aren't out there, just rare... again think about that when you are trying to get it repaired.

Now a quick note about wooden propeller blades in metal hubs. There is a lot of urban legend and general misinformation out there with regards to wooden blades slinging off of hubs because they are just held in place with lag bolts. Yes, blades have been slung (is that the right word?) off of these types of propellers. Blades have also jettisoned off of Hartzell, McCauley, and several others. Yes, the wooden blades are held in place with lag bolts. Not Home Depot lag bolts but, rather, special machined bolts. These bolts have been tested are are very strong. The weak link is the wood. Many of these older aircraft were stored outside in the old days and suffered wood decay in addition to adhesive bondline delamination as you would expect. Poor maintenance practices are no reason to give any piece of machinery a bad rap. Interesting note here is that MT propellers built in Germany utilize "Natural Composite" in their propeller blades which is, well, wood. These propellers are the choice of most every aerobatic pilot out there.

In closing, if you choose an Aeromatic it is a fabulous propeller. If you find one in a closet somewhere and decide to install it please have the propeller gone through by Tarver or someone approved to repair Tarver/Aeromatic propellers.

Hope this helps,