Big_Boy_Wales

I have a Variable pitch prop with a marx decaperm motor. Does anyone know where I can find variable pitch prop units these days??
Regards
Gavin

LtDoc

Big_Boy_Wales,
I'm not aware of any being made commercially, but that doesn't mean that they aren't available. I would think that it would be a custom made item, though. (Don't break the one you have!!)
- LtDoc

PS - Can I have it?

Big_Boy_Wales

Thats nuts, there has to be someone building these units if they were being done in the early 1990's. I had better look after mine well so I am afraid you cant have it! :-)
Gavin

LtDoc

Gavin,
Oh well. Guess I won't hold my breath then. What's the approximate size of you VP prop? I can't remember ever seeing one, especially for a boat (aircraft, yes...boats, no.). I can think of how a 'constant speed' prop might be made, but not a variable pitch. (Only one of several reasons why I'm not a millianaire!)
- LtDoc

Umi_Ryuzuki

Well I have some Ideas, but if it is that hard to come up with on of these propellers, then maybe I should develop it.

Who did produce your existing VP propeller BBW?

Big_Boy_Wales

Hello,
I will have to check the box, I believe it was a Marx as it has a Marx decaperm and reduction on it. I can tell you exactly how they do work as we had full size tugs with them in. They are very simple.
Regards
Gavin

Umi_Ryuzuki

Well actual plans would be nice, If you have access to them.
I figure anyone can "design" a variable pitch prop.
There's a poorly planned one in my head already.

The trick is finding a way to produce, or manufacture them at a really small scale.

Big_Boy_Wales

Hi ,
I will try a get a photo for you today of the unit I have. Its very simple. It has a hollow shaft with a pushrod through it. It presses against a thrust plate inside the prop hub. The hub is two plastic parts which when asembled capture the three blades. Each blade has an ecentric pin that is pushed against the thrust plate via spring preload. Its sprung posistion is full ahead and a servo connect via the pushrod gives it spring compression to move to neutral or reverse.
Regards
Gavin

Umi_Ryuzuki

Pictures would be nice also.
I would like to see how the servo operates that interior thrust plate.
I was thinking it had to be more like a swashplate on a helicopter, and move
the blade control pin on the outside of the main shaft
The spinning shaft would make it difficult to connect to the interior.
However, it makes more sense, to be inside the shaft.
So I am really curious how that piece works.

LtDoc

...Hmmm. Since the idea is to control the length of the pushrod, sounds like the easiest method would be to connect it solidly to the motor, then vary the distance between motor and prop. If the prop was mounted to the transom and not just on the end of the drive shaft, you wouldn't even need a pushrod, the drive shaft could take it's place. Fore and aft for pitch, spin for prop speed.
Or, mount the 'pitch' servo directly over the prop hub, run a shaft down to the prop hub to 'tickle' the thrust plate.
Or, mount an induction coil in the prop to control the thrust plate... 'course that would mean a bigger prop hub... ah, forget it.
- LtDoc

Kmot

My Feedback: (24)

Umi_Ryuzuki

Oh, ok I have it now,...

What your saying is mount the propeller on a fixed tubular hub, then run a rod thru the hub and mount it to a motor with an extended u-joint, or slotted tube. Then perhaps a disc mounted to the shaft could then be pushed in or out. That shaft would then control the pitch of the blades, and spin them around the fixed hub.

Another Idea,...

Gear drive a brass tubing propeller shaft around a solid push rod.
The tube shaft will spin inside the stuffing tube and around the control rod.
The motor will be mounted to one side of the shaft, so the servo can directly
contol the push rod, the thrust plate and the propeller angle.

Hmmm, now to get someone to build it.


Nice gif Kmot, but can you make it work in a miniature scale?

LtDoc

...Or, prop mounted on a fixed strut. Pitch control rod runs down through the strut to vary pitch of the prop. Use any kind of drive shaft and motor connection. Guess it just depends on where you want the 'complicated' part to be. Now that the hard part, thinking this stuff up (or stealing the idea), is done, all you have to do is find a mechanic to build it. I'll leave that to you! ;-)
- 'Doc

Umi_Ryuzuki

Hey, I'm no thief.
Well I do make my living on other peoples Ideas.
But only because I can build, for them, what they can only dream. And they pay me for it.


I have lots of ideas built on others theories, Some of them I see
mass marketed only one or two years after I prototype something.
Which just goes to show I have a slow mind. I figure it takes at least
six years to mass produce something properly.
And Out of all my Ideas only one has made it to market so far.

I must make about 30 bucks a month on that one.

So I wouldn't put much stock in seeing a mass produced
"variable" from me, but I would like to see if I can build a nice one.
Of course now that I have thought about it there should be one from Graupner, or Robbe in about two years.

(It actually took Graupner about 5 years to re-release the voith schneider I had been trying to build all that time.[I bought two]) The rubberband helicopter I built this Summer,...? There's a Frenchman mass marketing them now.[]

So now you know I have expectations for product in the future[8D]

Kmot

My Feedback: (24)

Hey there Umi, name some names! What have you designed that is now in production? BTW I think that's very cool!

Here is a plan for a variable pitch screw I found:

LtDoc

...You know what they say, "great minds think alike". Then again, with my 'C.R.S.', I probably saw it somewhere. Oh well, I didn't really wanna be a millionaire anyway...
- Doc

Umi_Ryuzuki

I think you misunderstand me, I have a lot of Ideas, but someone else
usually brings them to market right after I build a prototype.
Which means someone else had the Idea years before me.
The plans you posted kind of point that out Kmot.
I designed a lawn aerator, and gave a prototype to my
brother-in-law. It was designed to pop a "lawn plug" out of a
small yard and the home owner could aerate the lawn without
renting or buying a huge machine.
The next year the "weedpopper" came out. How annoying is that?
Same little design, but different use, and mass marketed.
I am obviously six years slow in the market place don't you think?
Think the "George Foreman Grill" is a new Idea?

However, I have a small model kit in production
A workbee from Star Trek.
It started off as a joke. I told a bunch of guys that they should make
little car bodies that looked like shuttle craft. Then that the shuttles
should be "Work Bees", so that they could have cargo races, or
play "hungy hungy Hippo" and see who could get the most boxes
to their side of the table.
They said, "Ha ha ha, you do it."

I came back two days later with a working model.
http://groups.msn.com/ModelersAndHob.../workbees.msnw

I got six e-mails asking if I was going to produce a kit, I said,
"No, it's too easy to do yourself." One guy was really persistent,
so I embarked on a mastering and casting endeavor. Once I got
started, it became evident that if all I did was finish the bottom of
the master to "model quality" I could sell kits also.

Suddenly it was a whole new idea. I decided to add manipulator arms, and
then I devised a way to attach the manipulator arms to the model with out
glue. Magnets and a small metal plate. It took two months to master, and
build the vacuum and pressure casting chamber. And once I had a
dozen finished I sent out three demos. One of the guys posted the
demo on a BBS system and now I make 30 bucks a month.

And it really was only a joke, "make an R/C star trek shuttle craft. "
Remember my slow mind?,... Those R/C ones, they don't sell!
But the people that got those versions as demos say they are
real show stoppers in their collection.

You can buy a kit though.
http://www.federationmodels.com/
ACEng Dual Bee

(Lt Doc,... I'm not a millionaire either)

Aimee

Oh, yeah,...

Bearing races, that's a good Idea. That design is huge 3/4" hub?
I wonder if that could be reduced now a days. Those look like old plans.
Of course trying to squeeze that and three propeller blades in
there might need all that space.

sailboater

I am not sure if this will help much but Loyal Hanna Dockyard makes controllable pitch props. I have never ordered one from them and I believe there is a long wait to get one because they have to be custom made. They have a pretty good selection though. Their website only has a few, but the catalog has several more not listed online. Their controllable pitch props are 4 blades ranging from 1.2" to 2.4". The only three blade they have is 2" in diameter. The link is http://www.loyalhannadockyard.com/PROPS.htm and when you go to it you have to scroll almost to the bottom to get to the variable pitch props. I hope this helps,
Bryan

Big_Boy_Wales

Hello,
I got one from westbourne models in the uk for 38 pounds. 60mm od 3 blade from Marx. It was the last of old stock.
Happy hunting all
Gavin

iflynething

go here ...[link=http://www.rcuniverse.com/forum/m_78268/mpage_1/key_flies/anchor/tm.htm#78268]Aerobatic Plane w/ Variable Ptch. Prop!!![/link]

I hope that works

A guy named Mec.....(or his s/n at least) made a turboprop for an aerobatic PLANE....It was on a plane but I'm sure that it has the same concept......the only problem is how would you couldn't run whatever was changing the pitch underwater w/o possibility of water getting into everything.............

Big_Boy_Wales

I will send a picture of the CV prop I have. Its very nice and very scarce!! :-)
Gavin

Kmot

My Feedback: (24)

Wow! When was that produced?

Umi_Ryuzuki

Interesting, My impression is that it is variable pitch, but you set it befor you run, and can not change it while running. Is that the case, or is it like some of the others that have been discussed, and presented?

Big_Boy_Wales

Look at the pictureon the box, at the opposite end of the shaft from the prop you can see the arm assembly that the servo connects too. So yes, I assure you it is fully variable forward and reverse. I have run it that way for 10 years . They were built up to 1992 by Marx in Germany, he has since retired but I did find one "new" old stock in Britain for 38 pounds. It was 60mm od and is identical to the one shown in the box. When I get a chance I will send a picture of the unit assembled. If you still dont believe me I will send you and .avi clip.
All the best
Gavin

Umi_Ryuzuki

It's not that I don't believe you, (boy people are so touchy around here)I was looking at the set screw instructions.
And it they seem to indicate that you can change the pitch by turning the screw.
Does that just set the maximums then?

[Edit]
Never mind, it is a set screw for the bulb itself that I was looking at, but the arrows on it seemed to indicate a pitch change. The arrows seem to actually be for the snap ring, and the bulb, on and off the shaft.

Oh yeah, I discussed this idea with my favorite machinist, and he doesn't think anyone would want one of these. He said there isn't market and people wouldn't pay for the cost to make these.
I guess, haven't quite conviced him, and He knows how much I paid for the Graupner Voith Schneider drives.