Author Topic: cox Pee Wee .020 tank mods (Read 5607 times)

Clancy Arnold · « **on:** May 12, 2007, 03:05:20 PM »

After reading Ray's comments about why the small metal tank on the Pee Wee .020 had been designed for FF, I now knew what was needed.

There have been pictures showing one hole being drilled in the side of the metal tank and a fuel line installed. It seems there should be a better way!

I decided to go about a weight reduction and also make it easier for use with an external tank.

Step 1. Layout where the ends of each slot should be in relation to the four mounting screws.

Step 2. Drilled 1/16 pilot holes, then enlarged them to 9/64, the diameter of the small fuel line I had in stock.

Step 3. Used my Dremmel tool and cut off wheel to remove the area between each pair of holes.

Step 4. De-burred all of the new machined areas to protect the fuel line. Cleaned the part to remove any metal chips.

Step 5. Pressed a length of fuel line on the fuel barb on the back plate and carefully reassembled the engine.

The big advantage with the modified tank is being able to inspect the fuel line all the way to the needle valve barb. It also makes assembly easier since you can see where the fuel line is in relation to the four screws. An added bonus is that you now have a choice of several places to bring the fuel line out from the engine.

One goal not realized was the weight reduction. The red metal tank housing weighed only 3 grams to start, and I only removed about 1/2 a gram.

Clancy

LARRY RICE · « **Reply #1 on:** May 12, 2007, 10:11:47 PM »

Back in the 70's someone offered a tank with several holes drilled in it for this engine (maybe Dale Kern). It seems that slots that you used should weaken the tank structureally, holes will not. Maybe I am wrong.
Larry

minnesotamodeler · « **Reply #2 on:** May 13, 2007, 05:39:34 AM »

I dunno, looks good to me...a guy could certainly take off too much material, but I don't think Clancy has. This is not a .60, after all.

A good feature, to be able to see the fuel line all the way to the barb. Don't know if you could do that with just a series of holes, but maybe so. With my current arrangement (one hole), I have to pull the backplate off to see whether the fuel line is still on or not. I like it!

--Ray

Bill Gruby · « **Reply #3 on:** May 13, 2007, 05:55:41 AM »

I have to agree with Ray (did I say That) the vibration and even the torque of this little "Jewel" is not sufficient enough to cause any kind of failure. YOU DONE GOOD CLANCY, let us know how well it works? Now if I could just figure out how to get you a "MILLING MACHINE" HMMMMMMMMMMMMMMMMM !!!!!!

"Billy G"

minnesotamodeler · « **Reply #4 on:** May 13, 2007, 06:43:29 AM »

Not neat enough for ya, huh, Billy?

You keep agreeing with me, I'm gonna start keeping score...

--Ray

Bill Gruby · « **Reply #5 on:** May 13, 2007, 07:06:49 AM »

I ain't been around for a while, how you boys doin Ray?

"Billy G"

LARRY RICE · « **Reply #6 on:** May 13, 2007, 07:44:22 AM »

I am sorry I did not explain, I crash more than you do I guess. A good hard rock, tree, or ground could bend the tank and offset the engine in ways that would not be good......or maybe not.

Larry

Bill Gruby · « **Reply #7 on:** May 13, 2007, 03:13:40 PM »

Larry;

Your thinking is OK.---------I look at that tank and see what looks to be about an .080 wall thickness there? You could litterally cut four slots in that tank leaving a 3/16 web at each bolt location and still have a unit strong enough to withstand a head on collision with a brick wall. The web width and thickness plus the stratigic location at each bolt will give you a tank just as strong as a full one. This train of thought comes from being a machinist for 40+ years. Again this is personal thinking and subject to discussion.

"Billy G"

LARRY RICE · « **Reply #8 on:** May 13, 2007, 03:30:18 PM »

well I'm out out of here. By the way the tank is pot metal not steel.
Larry

minnesotamodeler · « **Reply #9 on:** May 13, 2007, 04:16:21 PM »

I just don't think the engine has enough mass or speed either one to hit anything very hard. 'Course you could prove us all wrong, Clancy, by bouncing it off a concrete curb or something...I broke a Black Widow completely off its tank once (the tank bolts broke through the backplate, left the backplate still bolted to the firewall) but that was a BW .049, and a plastic backplate, and some pretty hard ground. I acquired some metal backplates after that. Got a picture somewhere...

Clancy Arnold · « **Reply #10 on:** May 13, 2007, 06:29:21 PM »

Ray
You stated that the tank is made of "pot metal", but it did not drill like pot metal. The markings inside and outside of the tank, makes it appear the it is a machined aluminum piece.

I Do not plan on flying it into a tree or concrete curb just to find out how strong it is! May happen anyway but not on purpose. LOL

Clancy

Bill Gruby · « **Reply #11 on:** May 13, 2007, 06:40:21 PM »

Clancy;

Look back, Ray did not say that Larry did when he left the conversation. Yes it looks like aluminum to me to, but I'm only guessing. You still did good. Now about that "Milling Machine"

"Billy G"

minnesotamodeler · « **Reply #12 on:** May 13, 2007, 08:59:35 PM »

No, it wasn't me who said that. If I were guessing, and that's all it would be, I'd guess (like Bill) the tank was some kind of aluminum, maybe spun? But what do I know? Now, the metal backplates, that may be pot metal. I know they're pretty brittle--I've broken some mounting lugs off. Still better than the plastic ones, though...

Robert McHam · « **Reply #13 on:** May 13, 2007, 10:14:59 PM »

I know little of what the tanks are made of or how they were made. I do know that pot metal is very brittle and like the lugs of the Cox metal backplates break easily. If indeed the Pee Wee tanks are indeed pot metal then they would be a poor choice to drill lots of holes in as it would weaken it immensely.
On the other hand pot metal does not lend itself well to machining whether it be turning, millwork or drilling due to its brittleness. That said, nonetheless it can be drilled and machined.

The metal tanks used on the Bees made by Cox do appear to be turned.

Robert

Paul Smith · « **Reply #14 on:** May 14, 2007, 03:54:18 AM »

Back in our younger days we did that to Babe Bees.

Only we went so far as to remove all the metal, all around, leaving the internal venturi tube supported only by the four naked bolts. It worked just fine.

In fact, all the bolt force was concentrated 100% on the O-ring seal, therby solving a nagging problem.

ps:
Given that the value of a stock Babe Bee tank was 0.0, nothing ventured, nothing gained.

Bill Little · « **Reply #15 on:** May 14, 2007, 07:27:21 AM »

Larry Renger can give us the skinny on what any part of a Cox engine is made of. How many years did he work there?? Oh where, oh where are you Larry Renger??

Larry Renger · « **Reply #16 on:** May 14, 2007, 09:07:04 AM »

I worked at C*x for a total of 9 years in two sessions about 15 years apart. Early 1973 to late 1977 and 1992 to 1997.

The engines are made of metal, plastic and elastomers. Or did you have specific parts in mind?

minnesotamodeler · « **Reply #17 on:** May 14, 2007, 12:31:56 PM »

Larry, I believe there was some question about the tanks being pot metal; others of us vote for aluminum...seems to be a consensus on the metal backplates, anyhow, as pot metal of some kind. Shed whatever light you can, please.

--Ray

Bill Little · « **Reply #18 on:** May 14, 2007, 12:53:36 PM »

Quote from: Larry Renger on May 14, 2007, 09:07:04 AM

I worked at C*x for a total of 9 years in two sessions about 15 years apart. Early 1973 to late 1977 and 1992 to 1997.

The engines are made of metal, plastic and elastomers. Or did you have specific parts in mind?

Uh............... how do I say this.......... YES!!!!!!!!

Look above in this thread. The question raised was the material used to make the .020 "Pee Wee" tank. Seems to be a difference of opinion as to what the tank is made of, and how.

Thanks, Buddy!

Larry Renger · « **Reply #19 on:** May 14, 2007, 04:36:23 PM »

Sorry, I really didn't pay enough attention. The tank is aluminum, it is a "screw machine" part which is turned down from an extruded bar of aluminum. Sounds wasteful, but the aluminum scrap is sold back for recycling at nearly the cost of the bar material. You essentially pay for the material in the final part, power and machine maintainance. I don't recall the exact specs on the aluminum, but it is pretty good stuff, well above beer can level. The crankcases are done the same way, except from a shaped bar (extruded aluminum) of higher strength material to withstand wear.

Sad to say, C*x has disposed of the Screw Machines, so you will never see an American made C*x engine again. I gather that CS tried to duplicate the engine, but couldn't make the quality. The designs are obsolete anyway.

Bill Gruby · « **Reply #20 on:** May 14, 2007, 05:09:20 PM »

Larry;

Thank-you, now that I know it is Bar Stock Aluminum, I am going to machine one of these as I said in my above reply. I will machine 4 slots 3/16 wide. I will leave a 3/16 web at each bolt position. I will put it in a ratcheting C-Press with a gage on it and see just exactly how much force it takes before it fails. This will be measured in lbs.Unless one of you has a better way to test it. I am open for suggestions here. If I do it my way it will be destroyed. You guys call it?

"Billy G"

Clancy Arnold · « **Reply #21 on:** May 14, 2007, 07:35:54 PM »

Bill
Don't waste a perfectly good tank. Larry has set the record straight on the machined tank. I might go back and "machine" some more off of mine just for weight reduction.
Clancy

Bill Gruby · « **Reply #22 on:** May 15, 2007, 05:36:21 AM »

To All;

Clancy is right, no sense in ruining a good tank for no good reason. This thought comes to me and you from none other than "BigIron 13" He suggested doing away with the tank entirely, just cut some tubing (Aluminum) the length of the tank and fit it over the four bolts and tighten them down. See there is more thn one way to skin the proverbial cat.

Clancy go ahead and remove all you want. I gave the tank to a friend who works in a "Metal Lab". He analyzed it for me, it is low end 6061-T6. That stuff has a ultimate shearing strength of 27 ksi. That's it I am done here see all of you later

"Billy G"

Larry Renger · « **Reply #23 on:** May 15, 2007, 08:26:21 PM »

Looking back at my last reply, I have to note that C*x produced more engines than the entire modeling community will use in our remaining lifetimes. All you have to do is find them!

The sad part of that is that there isn't a next generation who will be deprived.

minnesotamodeler · « **Reply #24 on:** May 16, 2007, 08:16:01 AM »

Quote from: Larry Renger on May 15, 2007, 08:26:21 PM

Looking back at my last reply, I have to note that C*x produced more engines than the entire modeling community will use in our remaining lifetimes. All you have to do is find them!

I suppose that's true...I've accumulated half a dozen .020s, plus misc. parts, without even trying.

--Ray

Clancy Arnold · « **Reply #25 on:** May 16, 2007, 06:15:48 PM »

Bill, Ray
I just measured the wall thickness on the Pee Wee .020 tank that I modified (Thanks for the new Calipers Bill!) and it measured .048 inch thick.

Clancy

Bill Gruby · « **Reply #26 on:** May 17, 2007, 07:32:09 AM »

Everyone;

A couple of things here;

1) It's been a pleasure hashing this one out with you guys, for the most part it was very informative.

2) Clancy, those "Digital Calipers" went to a good home, you are the only lefty I know.

3) Ray, you keep tallying up the score. I will be around.

4) Keep the chips flyin fellas I will be watchin ya.

"Billy G"

minnesotamodeler · « **Reply #27 on:** May 17, 2007, 08:47:46 AM »

Unbeknownst to you, Bill, you know another lefty too: me. (But I fly right-handed. But I start engines left-handed.)

--Ray

Bill Gruby · « **Reply #28 on:** May 17, 2007, 09:03:58 AM »

OK;

Thats cool, I'm right handed and fly with me left hand. I can lead the maneuvers easier. I am always ahead. Works for me. Thats why I sent Clancy the Calipers, they were for a lefty. I used to use them when training people on the lathe. I was always on the back side and had to read right handed ones upside down. Let me look in my tools I might just have another set, no promises, I will look.

"Billy G"

minnesotamodeler · « **Reply #29 on:** May 17, 2007, 02:18:55 PM »

Cool. I really wasn't hinting for one for myself, you know. But I would accept it with graciousness.

--Ray

Clancy Arnold · « **Reply #30 on:** May 17, 2007, 03:53:31 PM »

Ray
The Digital Calipers Bill sent me were in bubble rap as he did not have a case for them.

Now they do! The case was presented to me as a "Retirement Gift" when I left UMM Electronics, Quality Department. The case had the 9 inch ruler inside. Note the "Calibration Not Required" label.

Clancy

minnesotamodeler · « **Reply #31 on:** May 17, 2007, 06:32:48 PM »

I can't think of a much more useless tool than a 9" ruler, wooden especially. Nice case, though.

--Ray

Larry Renger · « **Reply #32 on:** May 17, 2007, 07:45:16 PM »

When my brother retired, they gave him a cheap Timex watch and a can of gold paint. Really!

Bill Gruby · « **Reply #33 on:** May 18, 2007, 07:12:37 AM »

Ray;
No lefts, got 7 sets of righthanded, will that do? If so PM me where to send them. GM was good to me when I retired.

"Billy G"

minnesotamodeler · « **Reply #34 on:** May 18, 2007, 07:32:05 AM »

Hey Bill,

Done. Now, you need any .020 parts? or anything else? Let me know.

--Ray

George · « **Reply #35 on:** May 20, 2007, 07:42:48 AM »

Quote from: Larry Renger on May 17, 2007, 07:45:16 PM

When my brother retired, they gave him a cheap Timex watch and a can of gold paint. Really!

If that paint is Krylon, it's probably not fuel proof either!

George