Rebuilding a Black Widow, mouse racer style.

Hey Rusty,
I just returned from a beach holiday & noticed your thread topic. It's excellent!
What you're doing is what I've actually always wanted to do. I've always though that a few short video clips of various phases of my Cox engine building/assembly would be a real help. But I'm not as far advanced as you are in that regard, so keep up the good work!
The whole Cox 049 RELIABILITY thing is based on sealing up leaks everywhere. I'm not sure if you sealed up the screw holes in the backplate (after the engines's all together) but if not, you should. Certainly when the engine doesn't needle properly you've got a problem that has to be fixed. Sadly, I've no way of trouble-shooting over the internet! The time-consuming way is to swap out parts & isolate the offending leaker. OR, use your intellect & attempt to FIX the offending leaker. Both ways work...
I'm not a great intellect/designer, but I do try to OBSERVE what's going on a lot.
One thing I observed was your comment that Sig 35% worked well on your TD but not with your reed motors. Something's wrong here. Induction style has nothing to do with how an engine responds to fuel type. You may note that Sig 35% was the selected fuel for the 2010 049 Tach Off & it ran well in all those entries... If I could, I'd like to take my Sig fuel over to your place & run your engine to see for myself. If only! So somethings's amiss there, but I'm not sure what exactly. You did however mention the condition of the plug. Now that's a clue. Not sure what the 'white haze' you describe is. I do know ANY "frosting" of the Cox element is not good & often is a sign of micro metal coming off somewhere. The real question then is WHERE?
It is possible your cleaning is not thorough enough, although that's a stretch. (i.e. not 100% of the grinding or polishing compound was removed...) Or, it's something else seen with a 10X magnifying glass. Or, none of the above. Very tough to diagnose over the internet!
You mention sanding the c/case to match the transfer ports. 25 yrs ago, I thought that was a great idea that made sense too. I did however OBSERVE that no Cox 1/2 speed flyer did that. They always positioned their exhaust ports sideways. So I deduced, they would do it differently if they though it was better, but they don't. I've OBSERVED on my best running mouse engines that the ideal port situation is neither front nor sideways, but at a 45 degree angle. I can't tell you why, but I know what I see...THIS is what makes these discussions interesting!
For bench running it's not critical, but for flying the fuel pick-up MUST be at the absolute most outboard corner of the tank. Your photo shows it's close but for me, it wouldn't be close enough. Your position (in the air) won't use all the fuel in the tank.
Mounting the engine cyl sideways has the benefit of more tip weight & more streamlining. About all I can say is do it carefully (whatever that means). I have seen some perfectly normal engines run very strangely when their owners moved the cylinders & tank around. It can work JUST FINE, I've seen that too, but one must be careful to OBSERVE, when these changes make things worse. One reknowned modeller claims his engine runs better (in the air) with the cylinder on the inboard side. Perhaps.
In any event, my method of operation is to start from square one & go from there. If a change is better, good. If not go back a step & confirm the observation. Speaking of which, I winch when knowing you're not using a Tach. Man, you gotta get one of those! I've got a spare for $30 delivered if you can't get one locally. Enough of my ramblings for now. Keep up the informative work.

Cheers, Paul



I did not know Paul G. was a member of CEF before I started this, but whaddya know, he's here. Now I better make it good. Paul, if you read this, I hope you approve. Or if you need to add some criticism, I'll welcome that too.

Thanks for the reply, Paul. I just came in from the shop, and I have it running as well as in the video I posted from yesterday. Trouble has followed that backplate around. I'm just now realizing that. So I put a real Black Widow plate on it(although it is plastic), and an OEM venturi gasket. It cranked and ran exactly the same during each of 5 runs. I can kill it by pinching the vents, although a little slower than It should. It needles at about 2.5 turns.

I wish I had read this earlier or I would have positioned the pickup tube higher. There is a little shelf at exactly the right place to prop the tube in a metal plate, but not on the plastic one.

When I run an engine all week on my Glowplugboy fuel, the glowplugs are fine. In fact since I was a kid I've only had 2 plugs fail until lately. And if after all that time on GPB fuel I can run a single tank of SIG through it and the engine will no longer crank. The ohm meter reads normal conductivity but it will not light. Something may be depositing on it that's more conductive than the platinum, shunting the current(in theory, unlikely. Platinum is very conductive), or shorting it to ground(more likely). A coating of fine steel or aluminum would surely do that too. But this is a problem across all of my reedies. I am ridiculously meticulous. I fiddled with those engine parts all week, and each time I re-bagged them, I cleaned them with alcohol or acetone. I inspect everything under my magnifying lamp before moving on to the next. I've been wondering if it's the batch of fuel. I have never bought SIG before I got this bottle of 35%. I have a bottle of SIG 25% also, but I'm too forgetful to keep straight if it's one or both of them. I Googled "SIG fuel foul plug" and came up with nothing. Maybe the TDs burn it off, I haven't a clue.

I did plug the backplate screw holes with black Permatex on the metal backplate. I didn't want to skip any steps that I didn't have to. Today I didn't seal them, but I will. Like I said, it's a little slow starving it when I pinch the vents, however it is consistent. After I open it up to move the pickup tube as you suggest, I will plug them then. If any more problems arise, I will also seal the crankcase with the same stuff. I have had two BWs I had to do that with and they became my fastest consistent runners. In fact this crankcase was from one of them. I figured the screws and shallow threads were the real problem, so I spent a lot of time with this engine getting that right. I expect my 2-56 bottoming tap will be in the mail tomorrow. I'll get it perfect. After learning your methods, now I can rebuild a dependable Bee much more quickly than the week of evenings I spent on this one.

If I was actually trying to build a mouse racer, I would have put a KB crank in it, and I would have tested it with a sub 5" prop. But its purpose is only to be a sporting workhorse for my fun and entertainment. Do you think I would see much difference if I had used a KB crankshaft?

After I move the tube and plug the screw holes I think this one will be ready to go back on the Li'l Satan.

Thanks for all the information, I'll be reporting my results.
Rusty

Hi Rusty,
Yes indeed, you may be coming to the right conclusion for the wrong reason. Certainly, if you OBSERVE a fuel doesn't run well, then by rights stop using it. I have no doubt that your particular container of Sig fuel is no good. Rare, but I have certainly seen & heard incidents of bad fuel from major fuel manufacturers...
Buying another new sealed quart would make for a good comparison. What's not answered is exactly what contaminant in your Sig fuel is causing the problem....that I don't know.

Concerning Killer Bee crankshafts. I'm not fastidious enough to say "the K/B crank gives 'X' more rpm than a standard crank under all conditions". One of the regular AMA mouse race winners never used anything but a standard crank. Personally, I've been able to go very fast with many standard cranks. When run really fast though, I broke them fairly regularly. I broke the original K/B cranks even faster until I started using a full length prop stud. The difference being in how precision a given crank was made. It was thought that in the earlier days of Cox (when people still cared) the general quality of parts was higher. Same holds true with the K/B cranks. Some run quite well & others are out of tolerance & vibrate or run poorly. Bottom line, for most sport flying you won't see much of a difference...

Looking forward to hearing more results & best of luck in your quest for high speed reliability.

Cheers, Paul

Are the KB Cranks lighter?

Godsey3.0 wrote:Are the KB Cranks lighter?

Yes. The web is trimmed down and the crankpin is hollow.

microflitedude wrote:

Godsey3.0 wrote:Are the KB Cranks lighter?

Yes. The web is trimmed down and the crankpin is hollow.

Your KB in the Tach Race would have undoubtedly spun faster if the prop screw hole hadn't been drilled crooked. You got burned by that piece of equipment.

Man, you all are wearing out my 'cut and paste' spies !!! We're gonna have to compile all this into a book or something ! Think I'll wait 'till tomorrow when my cloudy mind can wrap around all this great stuff !

Paulgibeault wrote:Hi Rusty,
Buying another new sealed quart would make for a good comparison. What's not answered is exactly what contaminant in your Sig fuel is causing the problem....that I don't know.

I've heard that too much anti-foaming agent will foul plugs. I think it's some sort of silicon compound. I guess they don't count a minute amount of that in their percentages, or it's included in the oil. or they don't use anything.

Kim wrote:Man, you all are wearing out my 'cut and paste' spies !!! We're gonna have to compile all this into a book or something ! Think I'll wait 'till tomorrow when my cloudy mind can wrap around all this great stuff !

Aw come on Kim, as you can see, I haven't overcome the engines' finnickyness. I'm just a monkey copying what Paul already figured out. He won the Bee category of the Tach race. My ear-tach says I'm not even close.

But I did like the way it cranked on the first flip. I swear I did not fake that. I'm going to tie up a couple of loose ends, move the tube position and plug the screw holes. Then crank it a few times this week. If it continues to be tight and reliable on the bench, it'll go on the plane for next weekend.

It was howling windy cold weather again today, so the Bean stayed in the hangar. It's new engine and fuel system is still untested.

I had some glow plugs with the "white haze" on the coil a few years back. Come to find out from a experienced racer it was from moisture absorbed into the fuel. Once I bought a fresh jug it went away. Every since then I have taken the fuel out of the clear jugs and put them into white opaque O'Donnell jugs. You get a greenhouse effect with the clear jugs if they are left in the sunlight or a warm environment. You can actually see water droplets form on the inside of the clear jugs. They always get put into a Igloo man purse/lunch cooler when going to the field on a sunny hot day.

PV Pilot wrote:I had some glow plugs with the "white haze" on the coil a few years back. Come to find out from a experienced racer it was from moisture absorbed into the fuel. Once I bought a fresh jug it went away. Every since then I have taken the fuel out of the clear jugs and put them into white opaque O'Donnell jugs. You get a greenhouse effect with the clear jugs if they are left in the sunlight or a warm environment. You can actually see water droplets form on the inside of the clear jugs. They always get put into a Igloo man purse/lunch cooler when going to the field on a sunny hot day.

That could be a problem. I keep the fuel in the house in the Summer, but it stays out in the drafty shop in the winter. I should keep it more stable. I'll add a cooler to my field gear too. Thanks for the tip.

I got my bottoming tap today. I'll thread those crankcase holes as deep as they'll go and use new screws. I'm ready to get this engine back on the plane.

My tap came today, so I ran out to the shop to play. First off, I fueled up the little Garnet and Black beast, still on the test bench. I've had such a rash of uncooperative reedie rebuilds lately, that I never trust an engine that ran fine yesterday to run at all today. So it stays on the bench until it proves it's worthy of flying. That, of course is what led to this project. I was happy to find that it started right up and ran smooth and fast at the same needle setting as yesterday. I burned up a couple of tanks, and can still kill it with a pinch, though a little too slowly.

Back apart and de-oiled, I cleaned all the old threadlocker gunk out of the Crankcase screw holes. The tap I'm referring to is a 2-56 tap I bought to extend the threads deeper into the existing holes. Prior to this, the screws would only go in between 4 and 6 turns. Here it is in hole number 1:

I used Marvel Mystery Oil. A little thick, maybe but probably good for aluminum. I worked the tap slowly and was able to extend the threads, so now I have between 9 and 10 turns on all of them. This is good because they aren't the tightest fitting screws in the first place. Here's my little reference again with the updated screw turns for each hole:

From 4.5 to 9.25, from 5 to 10, etc.
I would bet bottoming out the screws, or insufficient threading is probably what has caused every crankcase pressure leak I've ever had. I have high hopes this will increase dependability a lot.

I also went back to the aluminum pickup tube. I thought the plastic one was going to work, but when I repositioned it, it was too loose on the nipple. My aluminum tube(thanks to Microflitedude for the al) is a bit ugly, but it's clean and open and sits firmly in place with some fairly thick walled silicon tubing. I'll skip the twist tie this go-round.


I have some new screws for the crankcase and I'll check the length when I fit everything up tomorrow. And it should be ready for Mouse racer rebuild V2.0. As usual, I will make a video for your viewing pleasure.
Rusty

Thanks a lot for the green Rep points, whoever clicked it.
I only fiddled with glowplugs and filtered and spiked some fuel with oil today. It's too freakin cold in the shop tonight. I expect to have it running again tomorrow night. I have to solder up 4 new starter batteries too. I've been using the starter a lot lately, I drained a 4 pack of Energizers in about 3 weeks. And only flew once... badly.

Rusty,

There's no such thing as a bad flight. Some flights are just better than others.

Bob

fit90 wrote:Rusty,

There's no such thing as a bad flight. Some flights are just better than others.

Bob

You're very right, Bob. I did not break anything. Your old Tee Dee was involved until the bladder popped in mid loop.

Probably nonsense but I read somewhere that the rubber plungers on
the syringes we use can lead to minute traces of rubber in the fuel
which shows up as grey speckles on the plug element. Syringes with
nylon plunger would of course obviate this. Nonsense? Maybe.
But a great thread anyway, learning loads.
Now where did I put that 2. 56 tap?
john

proctor wrote:Probably nonsense but I read somewhere that the rubber plungers on
the syringes we use can lead to minute traces of rubber in the fuel
which shows up as grey speckles on the plug element. Syringes with
nylon plunger would of course obviate this. Nonsense? Maybe.
But a great thread anyway, learning loads.
Now where did I put that 2. 56 tap?
john

Dunno John
But if you can turn out some 2-56X1.25 bolts I'm your first customer...

proctor wrote:Probably nonsense but I read somewhere that the rubber plungers on
the syringes we use can lead to minute traces of rubber in the fuel
which shows up as grey speckles on the plug element. Syringes with
nylon plunger would of course obviate this.

Yes, rubber is not good for the glow plug. You should use dedicated glow-fuel syringes or plastic only syringes.

I replace them frequently. Even more often since this problem started. My son the chemistry expert thought the same thing. I bought a fueling syringe from Texas Timers, and a funny little priming syringe from some other glow plane supply. One of them was made by the same company as my old syringes, B-D, and the other was by Monoject, another medical company. They at least look the same. I'll look into it again just to cover all the possibilities. And we'll see what happens now that I'm only using one brand of fuel..

My favorite syringes have rubber stoppers....

microflitedude wrote:My favorite syringes have rubber stoppers....

I wouldn't toss em yet Matt, this would be a long term type thing. If you haven't had a problem already you are probably fine.

I've used them a long time with no trouble too. You never know if they changed the formula for the plunger though. I'm going to use them until I rule out thew fuel.

I reassembled it yesterday. There is one thing I noticed and thought I should ask about. Is it normal for there to be a slight amount of slop between the con rod and the crank pin when dry? I'm pretty sure I've seen it on older engines. When I polished the crank pin, I used a very light touch, I'm pretty sure I didn't tale off any significant amount of metal. I just noticed a click I hadn't heard before and when I looked, I could see a slight amount of play.

I'm going to mount it and crank it again today.