Rebuilding a Black Widow, mouse racer style.

Here's the vid. My ear-tach thinks(hopes?) it might be hitting 19k. Let me know what yours thinks.

That sounds like a happy engine Rusty.
Thank YOU
for taking the time to do the work and write about.

Nice work rusty and thanks for the vid and tips, conclusions, ect.

Thsi is just a point of observation, so dont take it the wrong way. I see you have a filter on your filling syringe, and as you filled it out of the container it looked to be in place. Doing it that way traps dirt on the backside(fuel jug side) of that filter screen, then when you fill you push the possible trapped dirt into your tank. If I am seeing that wrong or if it is a different setup, please correct, but that was my first impression.

If you would like, you can bubble pack send me those burnt glow plugs and I will take some 60X digital microscope pics and put them up,,to see what we may.

PV Pilot wrote:Nice work rusty and thanks for the vid and tips, conclusions, ect.

Thsi is just a point of observation, so dont take it the wrong way. I see you have a filter on your filling syringe, and as you filled it out of the container it looked to be in place. Doing it that way traps dirt on the backside(fuel jug side) of that filter screen, then when you fill you push the possible trapped dirt into your tank. If I am seeing that wrong or if it is a different setup, please correct, but that was my first impression.

If you would like, you can bubble pack send me those burnt glow plugs and I will take some 60X digital microscope pics and put them up,,to see what we may.

I think it's a good build. I meant to add in my earlier post; considering my limited resources for matching and tweaking parts, I think that however fast it runs, it's probably as good as that particular combination of parts can do.

After I draw up the fuel, I try to remember to give the plunger a punch to blast any trapped dirt back out. Maybe I forgot because of stage fright. I do need to come up with a better method, but at least I filtered the whole bottle of fuel on Tuesday before I added castor oil to it. Thanks for looking out for me though.

When I get some time next week I'm going to sort out glowplugs and test them all with a new battery pack. So far the one in the Black Widow is still shiny. I'll put a couple of the frosted ones aside to send to you, thanks for the offer.

Gotcha on the flush before filling,,good idea.


Sounds good, I'll PM you my address Rusty.

Godsey3.0 wrote:The typical setup I see is where the Needle Valve is Vertical and the pylinder is horizontal. Usually to the outside of the CL ring.

CZ: Would that not leave the NV exposed in an inverted crash?

I was thinking about this and the found that I had missed this question. Sorry - but it got answered. The key is stunt tank.

Rusty,

She sounds great! Smooth runner. You did a fine job on that one. Perhaps it's time to follow suit with my own widow. Loved the first flip start!

Good job man!

Ron

cribbs74 wrote:Rusty,

She sounds great! Smooth runner. You did a fine job on that one. Perhaps it's time to follow suit with my own widow. Loved the first flip start!

Good job man!

Ron

Thanks Ron. I like quick starts too. I've wasted enough time flipping stubborn engines that don't want to start. I have rushed rebuilds before and it is not worth it. It never saves time. I'm 100% sold on bottom tapping the crankcase screw holes. I think more hair-pulling trouble lies there than anywhere else.

Rusty,

PM sent.

Bob

Hi Rusty,
Congratulations on a job well done. That's a nice presentation that one day I hope to be able to do...
Few get my name right, but you did. It's pronounced Gee-Boe. (Thx for the credit)
I believe I noticed the starter spring vibrating like mad. The fastest running engines don't do that.
Why exactly it vibrates is a good question! I'm suspecting a less than optimal c/case to shaft fit, but that's only a guess... Or maybe that particular RPM range...but I don't think so. I'll have to see if my engines starter springs do that when I run them in the Spring (assuming it comes...)
I hope it runs well on your L'il Satan. Boy, that sure brings back memories...!

Cheers, Paul

RknRusty wrote:I made a video that I'll post to YouTube later tonight. I meant to mention Paul Gibeault's article that I used for guidelines as I intended to rebuild a clean tight fast engine, but I forgot to ask how to pronounce "Gibeault." I'm guessing it sounds like "Gibow," but I didn't want to butcher it. Sorry about that Paul. I'll put it in the movie credits.

Paulgibeault wrote:Hi Rusty,
Congratulations on a job well done. That's a nice presentation that one day I hope to be able to do...
Few get my name right, but you did. It's pronounced Gee-Boe. (Thx for the credit)
I believe I noticed the starter spring vibrating like mad. The fastest running engines don't do that.
Why exactly it vibrates is a good question! I'm suspecting a less than optimal c/case to shaft fit, but that's only a guess... Or maybe that particular RPM range...but I don't think so. I'll have to see if my engines starter springs do that when I run them in the Spring (assuming it comes...)
I hope it runs well on your L'il Satan. Boy, that sure brings back memories...!

Cheers, Paul

It ran okay. I was worried about being rusty after the Winter so I detuned it by adding a shim and propping it with a 6x3. Turns out I took too much spunk out of it, but I'll have it running better next time. There is a video if it flying in this off topic thread from yesterday:
http://coxengineforum.forumakers.com/t1812-i-loaded-up-the-radio-flyer-and-went-to-fly

One of our generous members gave me an optical tach, so now we can put the official stamp of approval on the Mouse Racer Style Rebuild project. I always thought incandescent lights couldn't cool and reheat fast enough to register 120 pulses/sec on the optical sensor. But they do. I have to turn out most of the lights and use a Mini-Maglite mounted to my test block, to shine through the prop. It works great. I made a fumbley movie of me using my new tach, trying to work the engine and the camera too, but I got the goods, and a sore finger too.

As usual, I'm too impatient to wait for the movie to process and upload, so I'll tell you now, the little Black Widow holds a solid 19.2k RPM through a whole tank. That's within the low end of Paul Gibeault's acceptable results. Certainly within mine. And the tach test was with a 5.25x4 prop. It was the best balanced prop I had at the time. So with a 5x3 it might do better, but no matter. Like someone on the forum said, RPM are cool on YouTube, but... uh, nevermind. As usual, video evidence to follow.

The previous vibration was evidently the prop. The spring stands pretty still now, so there is a new prop balancer in my near future. I can see there is no way you can run an engine this fast without a well balanced prop. I thought it was going to shred itself with that other prop. Turning a 4" pitch this fast says to me it's pretty strong. I noticed in the Cox test charts that pitch slows some of them down more than an inch of length. I'll probably fly it the first time with a 5.5"x3". That's what hauled it around so fast and tight the day before I rebuilt it. But for now, I'm moving on to testing out the Li'l Jumpin' Bean with its new power plant.
I'd say that about wraps it up.
Rusty

EDIT 4/24/2012: Here's an update with some different props:

APC 5.5x2 - 21,500 That's the fastest test yet.
APC 5.5x2.5 - 18,300 3.300 RPM difference with only 1/2" increase in pitch.
APC 6x2 - 20,300... on a 6" prop. That's a first for me.
Master Airscrew 6x3 - 16,300

Rusty,
Mission acomplished!
Thanks for sharing some realy nice work.
Music to my ears.
Bob

Rusty,

Great work. That little engine sounds awesome!

Bob

what cylinder are you running on that black widow, and btw where do you get 2-56 screws that long at?

A #1 dual port cylinder that was on the original BWs. Its bypass ports are deeper than the dual port cylinder that came on some other Bees. Not all of my #1s have the number stamped on them, and some numbers are on the barrel and others are on an exhaust facing. I got the no-number ones mixed up once and had to identify them by comparing the distance across from port to port.

I don't remember where I got the screws, but Radio Shack sells stainless steel 2-56 assorted length screws, nuts, and an assorted washer pack that contains #2 washers.

i cant believe you got that many rpms out of BW cylinder, it the crank an original black widow item too?

Yes it is, just a standard Bee crank. I always get more RPM with those, but the heavy duty cranks will stand up to the punishment better. The #1 is a good cylinder, especially if you get a snug fitting piston.

how many rpm's will a standard crank take, how long will it take say 20,000 rpms? i know you can get great performance out of a good fitting cylinder and piston

In my opinion if you stay with 25% nitro you will never bust a crank, you will wear out the crankcase pretty fast running over 19K.
The most I ever got out of my Meeces on 25% was 20.5K the crank was fine, the case is toast in about 15 runs.

crankbndr wrote:In my opinion if you stay with 25% nitro you will never bust a crank, you will wear out the crankcase pretty fast running over 19K.
The most I ever got out of my Meeces on 25% was 20.5K the crank was fine, the case is toast in about 15  runs.

Makes me want to stick with my 6x3 props.

Phil