[klick0]

Diarmaid,

tractor and pusher basically can equate to clockwise and counter clockwise. I think this is primarily because gas engines spin only in one direction, and if you wanted to make a pusher airplane, you would need a prop that works that spins the other direction, but rather then say that, they call it a pusher. I have bought probably 14 propellers from zinger, i buy in pairs of pusher/puller generally, and they are clockwise and counter clockwise.

3 bladed:
http://www.zingerpropeller.com/3_bladed_Propeller.htm
All of the those have tractor and pusher, upto 28 inches on this one.

You can't spin a prop backwards, if that was what you are asking, it won't work. Plus visualize in your head what would happen if you flipped one over, the pitch would be the same. Running in reverse would probably produce 50% of the lift it would in the right direction, granted i'm guessing, but it would't be good.

As far as the conversion, not quite sure what they are going with there, most model airplane engines use cubic inch, to convert that to cubic centimeter, multiple it by 16.4. So a 1.60 cubic inch engine is like 26 cubic centimeters.. I'd verify with this: http://www.onlineconversion.com/volume.htm

If yer trying to figure out what prop to use, a lot of people use this:
http://freespace.virgin.net/barry.ho.../thrusthp.html
I've used it for a while, then put the prop on a test stand and gotten different results, clearly it's not perfect, but gives you an idea. For electric motors it's hard with out a torque curve type chart to help you determine what size prop with what power will hit what RPM.... after a while i just ordered a bunch of props and tested them all out for an electric motor i got, reality is much better. Just call zinger propeller on the phone, i'm sure they'll tell you what to get for the engine you tell em. zingers are meant for gas engines, so they had no sizing info for me, but they deal with gas all the time, so they should know.

Now let's see those CAD drawings man

Ross

[vulcom1]

If you do not know the engine size or power it is hard to reccomend a propeller. The comment on flipping it over is valid as the airfoil shape is off. Maybe you should be going to variable pitch as then you can adjust it to what you require. If you do a search you will find them from models up.
John

[diarmaid]

.

[fyffe555]

Tractor prop is simply a prop that pulls the thing along, hence is at the front. Pusher, pushes from the back. Nothing technical. A tractor or a pusher can be clockwise or counter clockwise, or even contrarotating...

Props are manufactured to rotate either directions, as are aeroengines and boat engines and for the same reasons. Some twin aircraft have engines that both rotate in one direction, some have counter rotation. It used to be a serious argument between designers and buyers about the handling qualities of both. Even then they argued about whether they should rotate top tip outward or inward. P38's used opposite rotations, some models top in , some models top out, the Brits in stuff like theexport P38 and Mosquito used the same rotation on both.

Back in real life, finding a matched propeller pair in the right diameter and pitch for your selected powerplant will be the trick. Not least since Props are usually optimised for a given flight speed. You're going to be almost stationary? Also Ross and John are right, you need two props with different rotation and you can't use or modify one rotation to the other. The Ross's link to the Zinger's site shows different options for tractor and pusher which could suggest different rotations or just different boss mounts - they have four bladed in either so give them a mail and ask?

[diarmaid]

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[fyffe555]

No - you need two *different* props of the same diameter and pitch - but different *rotations* ..I'd ask Zinger about thier pusher and tractor props in the same dia/pitch as they are likely, as Ross suggests going to be different rotations..

When I said props are manufactured to rotate in different directions I meant that a props are manufactured to rotate in *either* a clockwise or anticlockwise direction. the same prop cannot do both!

[diarmaid]

Does anyone know of a way I can move this thread out of 'HOBBY PROJECTS - RAMJETS' and into the 'HOBBY PROJECTS - HOBBY DISCUSSION' forum???

[diarmaid]

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[diarmaid]

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[Kipper]

I think it needs an ejaculation seat or some such device before you test fly it! btw i'm in no way volunteering to do this...However I will come over and video it :lol:

[fyffe555]

[B]2 In this scenario its much better. Shut down the engine if only one prop has failed and glide down. When I say 'glide' I mean a very steep descent! But when the altitude is low slightly pull back the vehicle until it slows a sufficient amount and then at the last moment wrench it back to verticle and pull your legs up to your chest. The vehicle will only actually 'fall' about 10ft and the structure should take the slight bang on the ground. Pilot escapes with a few bumps and bruises like falling off a wall!

Ah - no... sorry chap but I'd have a read about potential and kinetic energy and conservation of energy. If you're 'flying' at , say, 100ft and your lift system fails and you have no other means of reducing the rate of decent you will hit the ground at the same speed whatever path you might take. Your idea above ignores the fact that as you decend from a given height in your 'glide' your speed increases, when you turn back up you exchange speed for height once more , it will only slow to a 'sufficient amount' once it's back up to almost the starting point. The 'Almost' is due to the loss of energy due to drag, which increases with speed but even terminal velocity, where drag and gravity match, would still be lethal.

With a helicopter you can auto rotate and so have a fallback system, with your system you have no controlable fallback so you need to add one, parachute maybe...

[diarmaid]

Hi folks.

This entire thing has just been cancelled. I talked to some knowledgeable aero type people who explained to me many different, varied and upsetting reasons why my design wont work. Seemingly it was :bs:

The plans are (flame2) and I dont even want to talk about them so don't bother asking for details of what my idea was after spending so long working on it. I'll try to think of a new way to go about it, but its done for the immediate future. Im sorry to everyone who was following this thread.

If anyone has their own ideas feel free to continue the thread but Im done for now.

Thanks for everything

[keebler303]

I think it needs an ejaculation seat or some such device before you test fly it! btw i'm in no way volunteering to do this...However I will come over and video it :lol:

I believe you meant ejection seat. I'm not sure exactly what the other type would consist of.
:nono:

Matt

[diarmaid]

lol. This thread has really gone downhill! But while we're scraping the bottom of the barrel, maybe building an "ejaculation" seat could be a new project for someone (Please don't post any pics)!!

Although Im also slightly disturbed by this and really dont know how or why or what for that would be built.....

[Kipper]

Thread is finished (spoilsport) great idea though :yup: I just bit the waggers finger....cos i'm like that

[willw00ds]

Hey guys im kinda new to this but already i can tell you i like this website. My name is will and i am really glad that i stumbled across this thread on google. I noticed you were talking about pavs and rocketbelts. Ive been somewhat working on a design similar to the solotrek and i found this site while looking for a good site that sells ducted lift fans. I was wondering if anyone knew of any besides the one posted above. thanks.

[willw00ds]

hey guys im new to this site but i am glad i found it. Diarmaid i think you and fyffe's ideas are cool. I have been working on an idea similar to the solotrek. I was looking for a site (besides hoverhawk) that sells ducted lift fans for my idea when i stumbled across this site. I read one of your threads from last month about pavs and rocketbelts and i was very intruigued. If anyone can give me a good lift fan site it would be much appreciated.
-will

[diarmaid]

Hi will. The idea I ended up with was also an adaptation of the Springtail (Solotrek) which I believed would be not only cheaper and more simple to produce, but also have various other advantages. I could'nt find any site to buy a ducted fan over a few inches in diameter unfortunately but if I do I'll let you know. I deleted the text from a large number of my previous posts so you were probably unaware of the route I decided to go down which may have been similar to your own. Im sure you've seen this but here's the current Solotrek (Now called Springtail) site. http://www.trekaero.com/

[Geof]

diarmaid maybe you should be talking to these people:

Skyflyer Technology GmbH ("Skyflyer"). Skyflyer is a company based in Wegberg, Germany engaged in the development and commercialization of a one-person recreational flying device.

[diarmaid]

Thanks for the info Geof. A four fan adaptation of the aerotrek crossed my mind to allow 2 or 4 person capacity. It looks like an interesting and kinda unique design, although maybe a bit slow. But hey!...if it works...more power to 'em.

Here's the site if anyone's interested:
http://www.skyflyertec.de/en/the-idea/

Referance post 72, I don't give up that easy....I still have an idea in the works that unfortunately has to stay very 'hush hush'!