ProBroJoe

Hi guys... sorry for this being kinda "outta the blue", but I finally got around to making a video of the geared cox twin that I built last spring and I thought some of ya'll might like to have a look. Here it is, filmed yesterday, spinning a Master Airscrew 8x4 at 10,500 RPM on standard 15% fuel. It has a 1.2:1 gear ratio, so each engine is turning ~12.7K...

Enjoy!
-Joe


I had to temporarily remove the video because some eBayer was using it to promote the sale of one of his items without my permission. However, the video is now back up. More info can be found in this thread:

http://www.rcuniverse.com/forum/m_4030265/tm.htm



[link=http://pws.cablespeed.com/~webster/Cox Twin.wmv]Geared Cox .049 Twin Video[/link]

BMatthews

Lovely!

But it occured to me that only one of "us" could enjoy watching a video of a prop spinning to the tune of snarly exhaust and enjoy it...

Dukester

My Feedback: (31)

Daddy likes

But it doesn't really look all that useful, so why don't you box it up and send it to me and I'll keep it for you..........

Did you use the guide that was posted on here last year to put it together?

Duke

brocja01

How do you start something like that? Do you start one side then just put the glow plug on the other side and wait for it to fire?

KidEpoxy

My question is:
Why did they stop at 2?
plate 4 of them on that bad boy! WooHoooo!

ProBroJoe

Dukester, nice try.... Yes, it's basically the same version that AJC posted plans in [link=http://www.rcuniverse.com/forum/m_1199286/mpage_1/key_/tm.htm]this link.[/link]

brocja01; Yep, that's exactly how you start it... and there's no mistaking it when the second engine lights!

KidEpoxy; In theory it could be done, but you loose a lot of power though the gears... as is, this is a +6 oz engine and the power-to-weight ratio is pretty poor. (I have a .10FP which weighs about the same and will probably turn the same prop at 12k+.) I will admit though, I've thought about a triple....

-Joe

BMatthews

Can you say Anzani? ..... I KNEW you could...

Let's face facts here. For our smaller model sizes no twin is ever going to match the power to weight of a single be it a geared twin like this one or a proper twin with a two throw crank. So it comes down to the appeal of uniqueness. And that a multi cylinder engine has in spades!

I'm not sure about a 3 but didn't Tazanos or some username like that have a 5 cylinder geared engine at one point? And the massively heavy old Gmark 5 cylinder was a geared unit with a light cast bell cover over the gears. On that one I seem to remember that the exhaust was ducted into the bell and outleted from there in order to provide lube oil to the gears.

Another geared project that would be kind of neat would be in inline twin Cox pair with the rear aimed backwards and the two gears coupled to a long fore and aft shaft. The center joiner could be custom made to provide a single carb to feed into an internal T to the two reeds. It would probably need to use either a fairly large diameter shaft or use a center ball bearing in addition to the two end ones. From there it would not take much more to extend the center manifold and backplate option into a double sided affair and bingo-bango-bongo you have a flat 4 running to a common shaft. At that point I'd offset the shaft a little to one side to allow the use of significant gearing down of about 1.7:1 or so and the turning of a 12'ish inch higher pitched prop.

subarubrat

My Feedback: (1)

I have said it before and I will say it again, wouldn't it be great if someone would do a production run of the machine parts and sell it as a kit. If someone would just tool off a run of plates and gears (or just provide the part numbers for the gears) to make that 3 cyl we could all go get our 3 pack of surestarts and build away.

combatpigg

My Feedback: (3)

That's *****IN' JOE! I would blow up a DNU about 125% and put those 2 in the nose.

KidEpoxy

It is not so much the Power to Weight, but the Freakin Awsome to weight is thru the roof.

ptulmer

My Feedback: (5)

Kid, you hit that one on the nose! Nice job Joe! I'm pretty much seething with jealousy.

MJD

My Feedback: (1)

I wish the video was longer. It's so soothing. I keep looking at my .010 collection and wondering.. nah, that's silly. But it would sound cool wouldn't it? So would a pair of gnarly combat .049's geared down. Hmm.

Hey ProBroJoe, is that a Pfeffer .036 in your Avatar?

MJD

av8rsodt

My Feedback: (23)

Joe,

What 3D CAD program did you use to create that triple-cyclinder engine?

I would like to learn more about going from 2D to 3D.

Thanks,
Brian

mgnostic

I ran my video player on loop till my wife threatened to beat me

ProBroJoe

Bruce... thanks... like I needed yet another project!

I'm pretty sure this is what you had in mind, of course missing is the front and rear bearing supports, the manifold, and various other bits... I've retained the stock reed assemblies by cutting down the backplates (thinking that the stubs would "plug" into the manifold with the RC carb attached). The whole assembly could be held together by running long studs front-to-back from the bearing mounts with the manifold sandwiched in between... of course it's still a pipe dream at this point.

-Joe

subarubrat

My Feedback: (1)

I am tellin ya, make a run of the plates and shafts for that tri-radial, or that flat four and we will round up the gears and bearings and engines and finish them off. I wish I had the skills and gear to do it myself but I don't and allot of us here are in the same boat.

build light

Hear! Hear! subarubrat, I second that!

mgnostic, Funny, your wife doesn't understand how wonderful that sound is.

Robert

ProBroJoe

subarubrat - I wish I could offer it too! I don't have the time (nor facilities) to pull off something like that right now... Heck truth be known, the project is stalled at the moment because of other priorities, but when I get around to finishing it, I'll drop back in and see what kind of interest there really is. At the least I'll make the drawings and part files available to those who want to have a go at it.

Thanks CP... I don't know about a DNU, but I'm definately going to have to fly that bugger in something, someday... I had planned on scaling down a Kadet Seniorita for my .10 FP, but I think I'll have a go at it with the twin first.

PT - If you ever get that lathe/mill, it would make a nice first project! Hint, hint, wink, wink....

MJD - The engine in my avatar is one that I designed and built, it's a .056 ci all barstock engine. You can read more about it here: [link=http://www.geocities.com/joby19672002/NGEZ-1/NGEZ-1.html]http://www.geocities.com/joby19672002/NGEZ-1/NGEZ-1.html [/link] There's a short video of it running along with a bunch of other pictures (and plans information).

Brian, I modeled the triple in SolidWorks - I'd be lost without it!

ROTFLMAO!!! ...and I thought I was the only one that did stuff like that!

-Joe

BMatthews

PBJ, that looks TO DIE FOR! ! ! ! ! I know it was just a case of building blocking the already CAD'ed set together for this but I'm impressed at how fast you reacted. Come on, admit it. I got you hooked, don't I.... [sm=wink.gif]

I like the idea of cutting down the stock Sure Start back plates even if it is just for the reed holders. I'm thinking that the manifold block plate could be a black plastic like black Delrin or similar to keep the plate light since it would need to be quite thick to provide the intake manifold path. Other than that I'm also thinking that a light tubular exhaust manifold that runs into a throttle restrictor would help deaden the whine of a Cox multi and also provide some back pressure to aid with a low and reliable idle speed. This would be backed up with an proper RC carb as well.

KidEpoxy

So 4 .049s running the geared shaft, and a .010 spinning a supercharger for the quad's manifold.

BMatthews

So the 010 would then be the APU for the main engine?

ProBroJoe

Uhhh, who? Me? I dunno what you're talking about.

You read my mind about using Delrin for the manifold - it will be a sizable piece. Here are more some basic, rough ideas... Probably go with some sort of beam mounting, add "ears" on the top side of the manifold to screw the front and rear plates into, add some sort of exhaust mainfold, rethink mountings & weight savings, etc...

Hmmmm... it's almost starting to look viable. (Scary huh?)

-Joe

KidEpoxy

looks like a fair amount of SwissCheesing can be done on the gear plates too

Looking awsome, except for the yello needle, we need it Cherry Red or Kickass Black to go with the coolness factor of the engine

ptulmer

My Feedback: (5)

Alright, I might me a little dumb, but I don't see how you plan on bolting the crankcases to the center piece. Other than that, I don't see why this won't work and supply a flyable amount of power.

Joe, I'm still trying! Maybe Uncle Sam will give me enough of my money back this afternoon.[>:] The NG-EZ is going to be my second project!

Dukester

My Feedback: (31)

Just drill the normal mounting holes all the way through the front of the case. Then use 2-56 all thread and some nuts to clamp the cases to the delrin block.

Duke (who is supposed to be working right now)