coriolan

Started some work on the semi-scale 1/2A hydro, the main frame is complete but still a lot of foam carving to do! I reused the cowl from my old mono since it is about the right size and this one will run with a TD .049 with trottle ring. the skin will be all 1/64" plywood over the foam.

jetpack

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I worked on a vintage aftermarket Kirn Kraft 5 1/2 x 3 pusher prop tonight for a Silver Bee project I've started for my Lil' Swamp Buggy. Rough castings but it's a lefty and another pitch to try out. Hope it's one of my best ones...cause it took the most work..lol.

The motor I am building from a used 8cc tank version Babe Bee. The regular BabeBee tanks are only 5cc.

Basically starting with cleaning up the old backplate and needle, polishing the fuel bowl, fresh mylar reed (works better than the copper star reed), venturi seal and case gasket and a new crankcase/cylinder assembly. It has no sub-port induction being throttled but it is twin port. The Cox GTP heatsink might go into my TeeDee Atlas that was kicking around in the box.

I picked up the swamp buggy supposedly unstarted but the side doublers were already glued. No big deal though, it was bought more or less as templates.

I've been trying to think of a crafty way to route a throttle wire to the motor so there isn't a big loop of cable.

Attacking the crankcase is next it is full of bin damage and overall sharpies and burrs. A stainless washer will be fitted behind the brass drive plate when the crank goes back in.

The fuel bowl was checked and then lapped lightly into the backplate with some copper cream and should seal up with no leaks.

This has been about three nights work so far.

coriolan

The Sullivan goldenrod 1/32" and sleeve can be bent in very small radius for trottle applications, have used it for ailerons in .020 size planes.

jetpack

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A goldenrod isn't a bad idea. Used them in gliders before and yeah you can bend them down to an inch or so radius. I was maybe thinking of using a bellcrank tucked inside the engine pod wall with the servo pushing straight up to it, then a rod to the throttle sleeve from there. I'll just wait until I have the kit out again and look but it's been something that's nagged me about that kit.

Speaking of nags, I got one out of the way today after work. I hung out for a little bit and spun me up a starter pulley for my 1/2A's. I used 1" stainless round and eyeballed everything but the set screw hole. I didn't do too bad working by memory on the V groove to match a Dumas flywheel. I checked when I got home and I think its close enough to work.

There was really no room or strength for the stock starter cone you see next to it to be cut with a V groove so I decided not to touch it and just change it out.

After it left the lathe I chuckled to myself thinking it would have been easier to just start with a stereo knob...lol...because thats what it almost turned out looking like.

Your hydro project is great to see happening. [8D]

Hey Robot I bet you wish you had one of the starters eh

coriolan

A starter do makes life easier with 1/2A, have been very happy with my trusty old "Astroflight mini starter" and for bigger engines I use a home made unit unit based on a 700 size motor. The hydro is coming along, still need to form the sponsoon and top before skinning and I think the mini "Wild thing" will be finnished first!

zeroskin76

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hey guys new to rcu forums but was directed here to get some info on building and running a moddified cox on a dumas dv10

ive built a mount for motor and put in the drive line
ill be posting pics soon

are those .12 outrigger still available?

Will Sgarlat

What will you use for a belt? I use 1/8" diameter round nylon cord from the hardware store. The ends of a length of perhaps 14 inches are paired together and melted using a butane lighter. When the tips are molten, butt them together to fuse, wait a bit for the nylon to cool but not harden, then roll the joint between thumb and fingertip to make it smooth. If you like this idea, or at least don't hate it, make several belts because they don't last forever. You get better at it with practice! At about a dime per belt, it's cheap and easy. Note: a broken, oily belt may not be repairable at pond or elsewhere. Above all, have fun!

jetpack

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Hi Will, I lucked out we have all kinds of big O rings at work and we order them too so Im going to be trying those. Your idea might even be better. O rings if not the right material are gonna melt with fuel.

Will Sgarlat

Jetpack: Good idea using o-rings for 1/2A starter belts! They're readily availible at the hardware store, too. They may/may not be grippier in the vee groove and if so, less tension may be required than with an oily nylon cord.

jetpack

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Zero, good to have you along. Anxious to see your boat!

The riggers are JAE 12's and are still being sold but I dont have all the info but easy to get. If you need to contact them let me know and I'll find out who if nobody posts.

Here's a full line up of Cox engines and accessories for reference. No fun not to leave any pics. [sm=teeth_smile.gif]

coriolan

Zippkits(in New York) has the kit for them.
http://zippkits.com/~zippkits/index....2451a7c8bdfa00
Here is the manual for the .12 JAE:

http://www.zippkits.com/12G2.pdf

coriolan

Interesting new head with more fins for Cox .049/.051, uses cheap inserts and might be usable with Merlin glow plugs:
http://coxengines.ca/product.php?pro...&cat=13&page=1
Can also be mofified for water cooling if needed! I have a few Globee 1/2A heads from my DF days and wonder if they can be used too. The Globee and Merlin have the flat coil element which is more durable than the Cox head.
http://www.merlinglowplugs.biz/Merli...list_10-10.pdf

jetpack

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I'll be looking into making some water jackets for those Glo-Bee's. If anyone likes to putt around making mechanical drawings and has an idea (I just make windows paintbrush sketches) go ahead and get a start at it because if I make one, it's just as easy to make three. It's the machine setup and tool grinding that takes the longest with this kind of stuff. Material cost is nothing. Let's finalize a design, everyone can have their input.

The clamp ring would have to be incorporated somehow because I don't want to have to make the threads unless someone would like to drop off a nice little CNC lathe for me.

I have all three sizes of Cox engine cases to make engine mounting plates out of aluminum on the mill at work to at least get started on that aspect of my hardware packs.

The extra finned head is really sweet. I'm glad to see it being offered because before if you wanted extra fins you paid a premium price for having to buy the Texaco head which is out of production.
By removing the center fins of the Merlin to open it up for water passage, two nipples could be put into the top and a piece of good heat shrink tubing put over the outside to make the jacket. It will want to shrink too much in the center maybe? Not sure. Another way is to notch the fins, or drill holes through the top.

I think the Atlas and SK Jr. would be okay with just those and a Bee engine, but not something like the DV-10 or Ske-Vee where the engine is burried. Especially if you're thinking of using a TeeDee or something with a sleeve throttle. The TeeDee would get blistering hot if I didnt cool it with a dumas jacket running no throttle.

coriolan

Some more progress on the 2011 1/2A boat build! the converted outrigger is complete and ready to try. The semi-scale hydro still needs lot of sanding but coming along nicely! I might have found a usuable pond not too far so all I need is warmer weather Will get some of these "Texaco style" heads from Cox international, Bernie confirmed that thes use the same insert as Merlin and Globee plugs and will provide a bit more head sink effect,zeroskin76 was lucky enough to put his hand on a Norvel heatsink for the Lite machine 1/2A helicopter which make water cooling unecessary even in his DeepVee-10.
Never been convinced of the need for water cooling with small engines, they need to run hot, have tried the Dumas 1/2A cooling clamp and it seem to be cast out of depleted uranium judging from it's weight.
Have made a few head sink along the line of the Cox unit for cars out of aluminium, some even with added water passage and I see little benefit. Even the .21 size boat engines can easily be over cooled which is very bad for an ABC P/L(ex: the old Picco-21 in the 80's with head&cylinder cooling)and only larger displacement engines produces enough BTU for heat to become a problem.

jetpack

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I think I might try using foam. Not a bad way to build with thin, soft wood like balsa or that mahogany sheet I bought. Your hydro looks really light.

My two props came in and have the 1427 cleaned up. Looks like it would be good on the .09 stock, but could work good cut down to the 1" plastic prop profile. It would give another 1/2" of pitch.

coriolan

WOF is a very convenient way to build boats, it makes the hull very rigid even with very thin skin (I use 1/32" & 1/64" plywood)and a simple balsa frame for hydroplanes. As a bonus it dampen vibrations and noise and add built-in flotation with very little weight penalty. Just glued my deck this morning (1/64" ply. While the epoxy cure I'll start to do more work on the "Wild thing"!

jetpack

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Congrats on the deck, thats always a good feeling.

Here's an old aftermarket throttle that was made for Cox powered chassis for road racing by Penn Racing Specialties. Anyone run one of these before?

coriolan

Nice find, Cox car disapeared a long time ago, $ 12 was surely expensive at the time!

jetpack

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Coriolan what have you been using to cut and shape your foam? Seems I've tried once and I couldn't get a consistent "cut" with any kind of sandpaper.

coriolan

Pink and blue foam cut very well with a saw or sharp kitchen knife for straight cuts. A band saw is also good at high speed,but mostly I use hot wire cutters and templates for curved lines (the same way used to cut foam wings). For sanding #60 sand paper is the maximum I use with light pressure and then use #100 or #150 sand paper to get it smooth. For the hydroplane I just glued the foam on each side of the basic frame(including the rear of the sponson and transom) and then follow the frame on top and bottom as a template. Then I glued the pad under the sponson and tack a template on top to cut the angle on the side following the curve. For the "non-trip" chine in the rear I just follow a metal ruler tacked on top (2 side tape) and run the hot wire with a bow along the side,hot wire produce a very fine cut and if a flat surface is needed no extra work. For the top of the hull the curve has to be sanded since it is a compound curve but there isn't much to remove from flat so not a big deal! Its kind of harder to describe than to do, should have taken pictures along the way I use regular epoxy for my build, it gives more time to position things but take overnight to cure (actually several days to fully cure)and hold everything with lot of masking tape. I avoid having glue near where I will cut with the hot wire latter because it will mess the cut. WOF is good for hydroplanes and tunnel boats but not for mono hulls, it is ideal to make a simple airboat like the Dumas Li'll swamp buggy with just a cavity for the radio equipment. I am actually thinking of making a basic air boat hull to try different power configurations (.049,electric+prop or electric+Ducted fan) by using different tops on the same hull.

Will Sgarlat

Jetpack,
Regarding the Penn throttle gizmo: Very cool! The bottom of the cylinder fits into it and I guess the servo motion opens and closes the three exhause tubes. You have to keep the thing all together with the package and the wordy, over-explained directions. I love it! You have a collector's item there.

Ron Olson

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Dave, good news but it's not a Dumas! Zippkits is coming out with a little 12" 'rigger soon that could be ideal for 1/2-A power. Joe was showing off their latest 18" JAE which might be too much unless someone powered it with something in between 1/2-A and A (.12).

jetpack

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Ron that throttle I just was showing gave me an idea. There's a few things you can do with the .049 to kill noise but not as much for the .09's and the .15 size Cox. There's just been more made for them than the other sizes. This throttle might be the answer due to the idea of having tubing exits. Might be able to route some large ID tubing into a muffler box inside the hull.

It can help beat the noise restriction at races for the Cox.

I can machine any size version of this throttle.

The .15 Cox Conquest (K&B makes them now) is a killer engine and would love to be able to race those in a rigger. If you never looked into them before they are a tuner's delight with case shims and rossi sleeves.

FastBoater

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How about a Diesel Cox Engine with a aluminum carb...you should be able to turn a bigger boat prop...what do you think jetpack.

robot797

i would kill for a carb like that

it is freaking awsome
yea i am still alive
did not find time to sail my ship (stupid rain)
when it stopes i wil sail it and film it