prole

My Feedback: (3)

So I have finially gotten it all together.

In hind-sight it seems really simple, but I am utterly impressed that Dickeybird has come up with this combination.

I am sure that you all know the premise, but the thread that this started in got long and I wanted to post some photo's along with what I had to do to get mine to work. This is my very first attempt at any sort of engine modification and I would have never been able to do it without Dickeybirds constant help and super concise directions.

I have only bench run it at this point, and without a tachameter I can't give any definitive results but it's obvious that it works beautifully. This engine at this point is the easiest Cox that I have to start, it is also the easist to get a strong needle. It runs consitently and is as fuel efficient as any Norvel.The throttle goes from a crawling whisper to a roar that is as loud and as strong as any of my stock TD's.

...and when you are idling and you hit the gas, you get it, no hesitation, not even a cough.

This is a picture of the whole thing showing the bushed down venturi, the throttle sleeve, the Texaco glowhead and the KK fine thread needle valve.

prole

My Feedback: (3)

here is a close up of the Venturi, it is two small lengths off K+S aluminum. one 1/8" and one 3/32" inside. The Venturi is drilled out just a tiny bit and all of this is JB Welded together.

prole

My Feedback: (3)

Here is a straight on shot of the front of the engine.

I started with three gaskets and settled on 5, the prop is a Cox grey 5x4 and I was using Norvel NVX 25%.

Everything else is exactly as Dicketbird suggested. The details are in this thread, just follow the link.

http://www.rcuniverse.com/showthread...57&forumid=161

I will post some more pics and a few other findings later, I just wanted to get this up early so Dickeybird could see it before leaving work for the weekend.

Thanks Dickey )

DICKEYBIRD

Ahhh, my heart swells with pride for you Tim! Glad to hear the little tricks worked for you. I have to say that these mods came about as a group effort, not all of 'em from this 'ol tired noggin. I have refined some of my ideas, Brian Pate (spindr) added his ideas and local engine expert Roger Armstrong helped as well. We just decided that we wouldn't stop until we got something that works!

Looking at your nice pix, I see you're running a grey 6x3 Cox prop? (Hope it's not a 6x4) Be careful, that's a lot a of load....if you have ANY trouble with sagging lean (hot) put on a 5x3...I run the black nylon 5x3 and the little critters love it.

HooRah!

ps: The stickers & Doculam went out in today's mail.

av8rsodt

My Feedback: (23)

Tim -

Did you use a lathe to turn down the venturi? I would like to get a setup so I can try this mod out.

Dickeybird - Can you post a pic of your "poor man's lathe"?

Thanks,
Av8rsodt

prole

My Feedback: (3)

Nope, no lathe...

I have a pretty basic setup, the only tools that I own that don't run off the power of my arms is a cordless Drill, a table top scroll saw(todays yard sale score 8 BUCKS !!!) and a dremel.

The aluminum bar stock that I used for the venturi mod is so soft that not only did I cut the pieces to size with a single edge razor blade, but I shaped it inside the venturi with a #11 xacto blade. I used a small buffing stone and the Dremel to smooth it out and did a few final shaping passes but other than that, it was mainly with the blades.

I used a small pen vice to drill the fuel intake holes through the new venturi. Those holes are small, not much bigger then the pins that I use to hold down my balsa work. It worked well. After that I just drilled out the main hole with a 5/64" bit and my cordless drill to get out all of the shavings and any of the JB Weld that had made it's way in there.


After doing this mod and seeing what my TD can do now, I would suggest that anyone who likes Cox's, and has a TD, should do it.

...and if you do decide to take it on, I had to get packs of the aluminum rod that you'll need. The LHS didn't sell these small sizes individually, so I have plenty. If you PM me your postal mailing address I'll drop enough for a couple venturi's in the mail for you...



just let me know, and you have to promise to let us all know how it goes


the prole

MR Flyer57

Hey Timothy,
I too have been following your progress and am very excited about your engine. This is the dream engine that I have always wanted and hoped cox would build.
I will make one of these up shortly and hope I have the same success you have enjoyed. These threads are long and I was hoping you could give me a list of which parts you ended up using and which engine they came off of, or maybe just a description of what to look for.
I will be waiting for your results and will be interested in the final package, to see how your plane flies.
Also did Dickybird have official stickers? Are these Dickybird engine stickers, because if they are that would be the frosting on the cake!! Please post a shot of the stickers if they are a Dickybird custom.

Still having engine envy,
Marshall

av8rsodt

My Feedback: (23)

Prole -

I will send a PM with my info - I would love to try this out.

I have been checking my TD's to see if they have the 2 channels inside the cylinder.

Av8rsodt

prole

My Feedback: (3)

MR Flyer57,

You have no idea how proud I will be to sport the "Powered By the Famous Dickeybird Cox" sticker on the rudder of the Lightning Bug. You're right, it's the icing on the cake.

I'll write out what I used and where I got it for you and Av8rSodt, and I'll send you guys some of that aluminum pipe that you need but just remember that I only copied what Dickeybird actually figured out. I can tell you guys how I did it, and what worked for me, but in the end he is the expert and he is the guy that you should go to with any questions on the theory of this engine.


...and DickeyBird, if you see that I have any mistakes here or have said something that is completely wrong, please call me on it. I am just trying to reiterate what I got from you, so just jump in if you see that I am screwing up...


***PARTS LIST***
1 Cox .049 or .051 TD
1 Texaco(5fin) or Baby Bee(3fin) Glow Head
3-5 head gaskets
1 piece of 1/8" K+S Aluminum Pipe
1 piece of 3/32" K+S Aluminum Pipe
1 Piston/Cylinder* Set
1 Throttle Ring (Ace or Cox?)

also-
JB Weld - available at any hardware store or hobby shop
Pin Vice with small drill bits

***ASSEMBLY***
As I see it there are two things that will take some effort, the rest is just either buying or finding what you need and putting it together. I was lucky in that I have spent way too much money and time collection Cox engines and parts. I had everything that I needed, but when I originally went through my collection looking for the cylinder I didn't find one. This is the hardest part of the engine.

***The cylinder MUST have 2 bypass ports and no Sub-Piston Induction***

That means that-
1. When you look through the exhaust ports as the piston goes up through it's cycle you SHOULD NOT be able to see under it as it passes through TDC

2. When you take the cylinder off the case and look into it from the bottom side you will see 2 small channels that run from in between the exhaust ports down through to the bottom. They are approximately 3/16" wide and 1/16" deep.

All of my TD's and Black Widows have 2 bypass ports WITH sub piston induction, all of my Baby Bee's and Golden Bee's have 1 Bypass port with no sub piston induction, For some reason I didn't even look at my Texaco's at first but when I did I found that they both have the special cylinder, and the needed glow head. I wound up using one from a brand new older Texaco that I had, it wasn't even broken it and it worked great.

However, before I found out that I was sitting on two of these special piston/cylinder sets I hit the eBay in search. Dickeybird had mentioned that there were cylinders that instead of having two big exhaust ports, one on each side of the cylinder, there were some that had two small pairs of exhaust ports. Those turned out to be not so difficult to find, I got 3 engines off ebay, not paying more than 10 a piece for any of them, all with the 4 slot exhaust pattern, and all of them turned out to have the special piston/cylinder set up. All of the ones that I got were on the "Product" engines, those are the ones with the plastic back plates with no attached fuel tank. In the beginning those were the only ones that I was looking at, but once I found out that my Texaco's had them I started looking on other engines as well. I found that on eBay just about all of the Texaco's had them, about 3 out of every 10 of the "Product" engines had them, and surprisingly about 1 in 10 of the Black Widows had them as well.

Unfortunately, eBay is the only place that I know where to look, my LHS sells Cox's, but only new ones and they don't stock much of any of the parts, just glow heads and glow clips. I would bet that if you could go to a swap meet or a show you could find a bunch. At the last swap meet in NC I got a handful of engines and Cox stuff for really cheap. All of my recent findings are from eBay. There are always thousands of Cox engines on there and if you just have to patience to sift through all of the crap, you'll find what you are looking for.


The 2nd step that takes a bit of effort is the Venturi Mod. Since you guys don't have to go hunting down the aluminum pipe you have one less thing to deal with. I has lucky in that my LHS has the whole K+S metal display with all of the music wire, sheet metal, and aluminum pipe and rod that I would ever need. You need to get two sizes, the smaller to fit snugly inside the bigger and the bigger to me the smallest size that will NOT fit through the hole in the stock TD venturi. The bigger size is 1/8" and it feels like you could almost push it through, you'll have to drill out the venturi with a 1/8" bit and make sure the aluminum pipe will fit through.

I cut 1" pieces of each. glued the smaller into the bigger, and then glued them both into the venturi. I set it so the bottom of the pipe was even with the bottom of the venturi threads and I sealed the gap on the bottom between the pipe and the venturi side with JB Weld. I let it dry for 24 hours, then drilled out the fuel intake holes on the sides of the venturi through the pipe that was now inside. There are 3 and they are tiny. Luckily I had a bit that small, but it was the smalled bit that I got with a "Micro Drill Bit Set" that came with my pin vice. You could probably poke through it with a pin. Once I got those drilled I drilled out the new hole in the venturi with a 5/64" drill bit just to clean out the hole and get out any shavings or JB Weld that had gotten in there.

At this point, I shaped the pipe that protruded in the venturi to match the existing angle. The pipe cuts easy and most of it came off with a #11 x-acto blade. What didn't I smoothed out with a small, fine grinding stone. I wiped it off, submerged it in gun oil and then put it in a small vile of denatured alcohol and shook it. All of that was in hopes that the oil would cling to any metal shavings that were still in there and that the alcohol would get it all off.

Now- just put it back together and fire it up.

A little experimenting is in order to determine how many head gaskets, and what prop will work best. I started with a 6x3 and 3 gaskets and settled on a 5x4 and 5 head gaskets with NVX 25% fuel.

WOW, this is really long. I hope this will clear it all up...

MR Flyer57-PM me your address and I'll send you some pipe tomorrow when I send out Av8rSodt's

the long winded prole

jboy381-RCU

tim, where do you find time to do all this stuff???all i have time for is work and sleep work and sleep.that is an awsome little motor.

are you ready to fly the lighting bug yet??i'm just dieing to use my video cam.i'll be takeing it with us to the fly in saturday.oh i almoset forgot PM me directions to your house ,if you still want to go.

we need to hook up one day so you can teach me about this 1/2A stuff.i like that i can fly in a field rear my house.the .40 size plane i have now is just to big.
talk to you later john

Big Al-RCU

prole
The one thing that I don't have in my inventory is the throttle sleeve. What is the tip-off in the e-bay descriptions that it is an engine with a real throttle sleeve? I have some 049s with mufflers like the QZ, and I see some 'R/C' 049s listed on e-bay but doubt that any of those are what we want. Some claim to have a 'R/C tank' whatever that is.
Thanks,
Al

DICKEYBIRD

Great job Tim....your spreading the word around is another step in my master plan to rule the world with Cox power!

Everything you've written looks good....about the only things I can add is that there are cylinders around that have no S.P.I. plus have the 2 extra smaller intake transfer ports like a TD. These give higher power on the top end but still idle and transition well. I've found that most of the later u/c RTF "Sure Start" engines with the grey plastic backplates and the intake extension tubes have them. They should be real cheap at yard sales.

The other thing is that I've been drilling the venturis to 3/32" (.09375') Yours being drilled to 5/64" (.078") probably gives you even better fuel draw and docility with just a little loss on the top end.

Anyway, this is your conscience speaking: "Step away from the nitro, get back to the building board!"

av8rsodt: Here's a pic of my "poor man's lathe", an old 1/2" B&D drill mounted with wood clamps to a plywood base with a switch/plug box to plug in my Dremel. A small adjustable light completes the rig. The bottom of the pic shows my rig for lightening pistons (oops, wasn't s'posed to let that one slip!) A piece of K&S brass tubing slit down one side is used to safely chuck the piston, a piece of 3/32" M.W. slid into the stub of brass tubing glued into the base holds the conn rod off to one side while I carefully grind off some metal from the inner side of the piston skirt. My TD's run smoother and faster with a 2.8 gm. piston instead of a 3.3 gm. piston. This is a trick I learned from my engine mentor Roger Armstrong. I just do it with my cheepo rig; he uses his fancy lathe! He's an ex u/c rat & mouse racer; they don't ever run out of things to try!

DICKEYBIRD

Found this pic of lightened piston:

av8rsodt

My Feedback: (23)

Wow, what a Plethora of knowledge... I am not worthy... I am not worthy....


Keep them coming!

Dickeybird - Thanks for the great hints! I know have a list a mile long of items I want to try. Wish I could make SMALL this year, but unfortunately I will not be able. Hopefully next year.

I would love to hear one of your engines run vs what I am used to: an 049/051 TD with some head gaskets, throttle sleeve, 10% cool power, and some fuel line over the needle valve.

Top of my list: tube down the venturi, proper cylinder, and now the lightening the piston.

1/2A Forever!
Av8rsodt

DICKEYBIRD

Hopefully, I'll get the "Gyrator" lightened up enough to fly better so that I can post some video on bipeflyer's website in the Design Contest section. I was planning on including a few seconds of start/idle/transition just to show the Norvelites that a Cox CAN idle and run well.

Your TD probably has at least the same or better top end than one of mine but with the venturi mod and cyl. change the idle speed, transition and fuel draw is much improved. I had a validation of the fuel draw improvement recently when I changed the cyl./piston ONLY in the "Cornbread" looking for more power to help in the hover and climbing flat spins. I used a known good (old style with the 2 extra transfer ports per side) TD cylinder with about .014" S.P.I. and found that the mixture change in nose up vs. level attitude was terrible! Very hard to "get a needle" that would work. I changed back to the cyl. with no S.P.I. and instantly the problem was cured. Go figure!

prole

My Feedback: (3)

Hey Dickeybird,

I got the stickers and the doculam, thanks I will wear it with pride.

I am beginning my 2nd Dickeybird Cox and have begun to stockpile the special pistons and cylinders. This one is in a .049 case too, but the next will be a .051.

I'm gonna try to thin out the piston too, this one is going to be a present for someone whom I owe big time, I want to make it even better than the first one.

I'm also wondering if you ever tried to remove the little piece of metal that separates the exhaust port into 4 small ones. Do you think I could take that out leaving just two big ones? Maybe better top end? What do you think about that?


Man, I got to get cracking on that plane, I'm all distracted by all of these New engines all over my shop...

Focus tim, come on man get it together...


timothy.....

DICKEYBIRD

Be careful with the piston lightening Tim....make sure you have enough spares around that you can afford to ruin some! Back in the local u/c reed valve racing days, I was lightening the piston on my BEST engine....you guessed it, I cut the skirt too thin and it crumbled. Couldn't sleep well for days I was so mad at myself! Just like setting a good needle, there's a fine line between improvement and failure.

The same thing applies to the "twin slit" exhaust ports. I do remove the bridge between the slits and I think it does increase the top end some but I don't have any numbers that would back up my theory. I have a CNC router and a special jig to hold the cylinder so that I can precisely grind the bridge out with a Dremel cut-off wheel. I can't in good conscience recommend trying to grind it out by hand. One slip and your cylinder's ruined.

My suggestion is to run & enjoy the engines you're building and wait 'til later to start expanding the envelope.

ps: Just got an email from Al Clark (met him at the Tullahoma S.M.A.L.L. event last year)....he's done up a "DickeyBird" engine as well and he's getting great results too! I guess this stuff really works!

MR Flyer57

Hey Dickybird,

I have a dumb question that after you answer it, I will wonder why I didn't know it already. What is (TD cylinder with about .014" S.P.I. ) S.P.I. ?

Years ago there was a lot of talk about balance of engine parts. There was a school of thought that some motors where left a little out of balance, the piston being light.
This was to allow for the weight of some carbon on the top. When you got them they was slightly vibration and after a few flights the motor got better when the carbon build up on the piston started to accumulate and would balance out the engine.

I always thought this was nuts, but I remembered the debate when I saw you trimming material from the piston.

Now with that long winded thought heres the setup for the obvious question. How can you cut material from the piston and not get a bad vibration?

Are the motors counterbalanced some how from the factory or is the whole thing just put together and left to shake?
I don't see how they could be balanced at all but I thought you might have been down this road, and I would like to hear your thoughts on vibration and balance in general.

One more little request, if I get one of the motors up and going can I get a Dickybird sticker? I would be glad to send you some cash for any expense involved.

Have you made a .09 throttled engine, and how did it turn out? any pictures and venturi sizes?

MR Flyer57

DICKEYBIRD

Hey there Mr Flyer,

S.P.I. = Sub Piston Induction or alternately called "Free Porting" It is used on cylinders that were made for higher power/rpm like TD's, Black Widows and the like. You can tell by the slight amount of opening under the piston bottom edge with it at Top Dead Center. These cyl's are fine for non throttle sleeve equipped use but to get a low idle, good transition and fuel draw, you need a cyl. without S.P.I. Apparently the mixture dilution caused by the use of a throttle sleeve on a cyl. with S.P.I. causes the problem. I have had some stock TD's that idle OK and run well with a throttle sleeve but for consistent running, I've switched all my throttled sport TD's over to cyl's without S.P.I. Cox guru Larry Renger has mentioned this in his articles on Cox power in Model Aviation a few years back.

The .014" refers to the size feeler gauge that will slide in under the piston at TDC. This is checked right after a piston/rod reset. The measured amount varies from cyl. to cyl. and case to case. For all out speed on a non throttled engine, you can increase the S.P.I. by carefully removing a few thou off the top of the crankcase, running less prop, more nitro and a pressurized fuel supply. Seems like I have run as much as .018" S.P.I. on my fastest runners. This is the kind of thing that requires much experimentation to get the best run on a particular day.

Any production engine is a compromise as far as balance goes. Some Cox pistons are lighter than others. I just remove some metal until they match the lightest stock piston I have ever measured....2.8 gms. I'm not sure but the Venom piston may be slightly lighter.

Never done an .09 but a friend has a .09 Medallion and it throttles great!

As far as the stickers go, sure let me know when you get an engine modified and running well and I'll send you some. Gotta get some more stickers out there to demoralize the Norvelites!

ajcoholic

My Feedback: (10)

You guys are making me jealous... I have lots of cox parts to fool with but so many projects currently on the go I cant try this one out... YET!

When I get my Whizard built I was going to use a Gmark 061 I found at a swap but now I am gearing back towards a Cox TD or Medallian as thats what I flew it with when I was 13. Cool!

AJC

MR Flyer57

Back at ya again Dickybird,
Thank you for the information, but as often happens an answer often leads to a follow up question. I got the S.P.I. now but when you talk about .014 under the piston at top dead center, what and where are you measuring?

When you refer to " after a rod/piston reset, i'm lost. I have a reset tool and no instructions on how or when to use it. I have just used it to eliminate extra slop in the rod/ piston area (where a wrist pin would be on a larger engine). Is there any rule of thumb as to how much slop is required here and is this the .014 that you mentioned earlier? If it is please give a quick how to, for measuring it. I can't think of a real accurate way to make that happen.
And thanks for the sticker info,,,, I am getting the parts together now!!
Mr Flyer57

MR Flyer57

Got one more quick question for ya Dickybird. Is the S.P.I a difference in the cylinder or the crank - piston - rod combination. I guess that what I mean is when I find and trade the stuff around would I need just the barrel or the complete set of parts changed?
Are all pistons/rods the same for the different engines of the same size?
MR Flyer57

prole

My Feedback: (3)

Hey Marshall,

I think I might be able to jump in here and clear up the first question until Dickey the Great comes to clear all else up.

Allow me to reinterate that S.P.I. can be viewed by looking through the exhaust port as you move the piston up towards TDC. You will notice as the piston get's just about to the top of it's cycle the you can see through the cylinder as the bottom edge of the piston goes up over the bottom edge of the exhaust port.

Go grab your closest TD and look. As the bottom edge of the piston comes into view you will be able to see clear through to the other exhast port under the piston.

The .014" is the measurement of the gap between the bottom of the piston and the bottom edge of the exhasut port. It is the size of the opening meausred by the largest feeler that you can fit in there.

DB is talking about making that space bigger by grinding a little off the cylinder. This in effect brings the bottom edge of the EXHAUST PORT down in relation to the bottom of the piston. The more you take off the bottom of the cylinder, the bigger that gap will get, the better hi speed performance you will get up to a point.


Does that help????


t.

MR Flyer57

Yes it is, I had the cylinder off while trying to find a why to get a measurement!

Also No gap is the one that is needed for the throttled engines, and some, to lots is good for a non throttled all out top end flier.
The cylinder is the difference and can be affected with a little grinding on the bottom of the cylinder.


Thanks, I hope the fog clears and I can keep up with all the information floating around.

Things are looking good again!!

Thanks for all the help
Mr Flyer57

Did you get my e-mail with my address? I would like to pay for any tubing that you send plus postage. You probably won't break even but you won't be supporting my habit as well as yours!

prole

My Feedback: (3)

MR FLyer 57,

I did get it, check you Private Messages, I wrote you the other day.

Av8rSodt- You check your PM's too, there are a few sitting there for you too.

You know that you can set it up so you get an email sent to you when some one writes you a PM, you can even set it up so you get a pop up message the next time you log on the RCU after you get a PM. Good features, I use the PM's a lot


sorry, I strayed from the topic, ... killer engines .... yeah!!! ....