Re: Testors/McCoy .049 smoked...

Marleysky Wed Oct 11, 2017 8:08 pm

roddie wrote:I have absolutely no experience/knowledge with these engines. It seems that both the AMF/Wen-mac and Testors/McCoy .049 engines utilize that heavy fly-wheel on the nose of the crankshaft in the form of a starter-spring assembly.. or otherwise. Was its purpose to keep the engine within it's design-rpm limits? Maybe the extra mass was needed for sustaining rotational-inertia to keep the engine running?

:huh:It's a heavy piece; to be fitted to such an otherwise lightweight engine-design.

I've always wondered why the designers put that heavy flywheel along with that extra heavy bolt and nut! Way back then building balsa models, trying to keep them light, and Testors comes along with this "nut job" airplane engine, tank and mounting conglomerateration!

gcb Wed Oct 11, 2017 10:39 pm

Jason_WI wrote:
Old-timers may remember the term, "slag engine." There were several engines made in the USA in the 1930s-1940s, sold mostly through a big store in New York City, that were junk right out of the box. They seemed to be made of the debris that floats on top of molten metal (slag), thus the name. Thor and Deezil were two of them.

Actually I had both the Thor and the DEEZIL. A slag engine was originally defined as an engine that both the piston and cylinder were made from the same material. In the case of the Thor, it was aluminum...very short-lived. It had space for a ring, but I found out it was for lubrication.
The DEEZIL was not a slag engine. From what I understand, the first ones ran fine. Later one were assembled without the skills needed for good fits so some ran and some didn't...mine didn't. I bought a replica with excellent fits and it is a good-running diesel.

George

roddie Tue Dec 05, 2017 6:26 pm

I made this bench-mount weeks ago.. and posted it somewhere.. (I thought..) Huh...

but not in this thread.

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What a mess my bench is.. Embarassed

Anyway.. I needed a tank-mount/shelf.. and found a bracket that's been kicking-around my work-table for days.. Rolling Eyes

So I decided to put something together. I used my trusty old B & D rotary tool with a cut-off wheel to shorten some screws.. and cut a matching piece of poplar-stock for the tank-shelf.

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I'm better-off getting these things out of the way beforehand. I may not test-run the Testors/WenMac engines anytime soon.. but when the day comes.. it's now just a matter of shimming a tank and running a feed-line. The mount is all set to screw-into a post on my deck out back.

I'd like to make bench-mounts for "all" of my engines. Most of them will be beam-mounts. It would be a good Winter-project. I like the idea of "dedicated" mounts.. rather than a universal-mount. I enjoy working with wood.. and making fixtures. Smile

rsv1cox Wed Dec 06, 2017 8:11 am

I made a similar one with poor results.

Despite being cinched up tightly in a vice the engine vibrated so badly due to the length of the board to the securing point it foamed the fuel. I think it happened on a Wen or Testors engine like yours. At first I blamed the engine (bent crank?) I finally resorted to commercially available mounts.

I posted about it here a year or two. Rod, Ron, or somebody recognized the problem and set me straight.

Edit add:

This might have been the culprit.

Testors/McCoy .049 smoked... - Page 3 Wen_ru11

Of course, yours looks a whole lot better screwed together than my hastily constructed example so it may work fine.

Bob

roddie Wed Dec 06, 2017 12:15 pm

rsv1cox wrote:I made a similar one with poor results.

Despite being cinched up tightly in a vice the engine vibrated so badly due to the length of the board to the securing point it foamed the fuel.

Of course, yours looks a whole lot better screwed together than my hastily constructed example so it may work fine.

Bob

In your photo, the mount isn't "centered" in the vise-jaws.. which would amplify the "spring-board" effect. You can see the difference in the jaw-gap on either side. The wood appears rather "thin" as well. A short-arm commercial mount will lessen the effects of vibration.. but if the engine or prop has a bad-enough balance-issue.. it's going to cause problems in a model.

I try to use clear solid-hardwood for a bench-mount if I have it.. and yes; I usually anchor the mount to a deck-post or rail using two long woodscrews.

rsv1cox Wed Dec 06, 2017 1:34 pm

Back when I was running every new to me engine I built many test stands, some famous, most infamous. Maybe 7-8 altogether. Individual custom stands for everything from Cox to Spitzys. That one probably wasn't the one that caused the vibration problem. Most were built per your example on the spot using 1X2 pine without much consideration.

I think this picture shows the villain under the larger stand, built for either a Cox or tank mounted Wen Mac out of thin T1-11 siding. It vibrated like mad. I think yours will probably do just fine. I couldn't find the thread I posted about it, probably fell off the end of the earth.

A couple of months ago I threw all of them away replaced by commercial stands.

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Bob

NEW222 Mon Nov 19, 2018 10:29 pm

I hate to bring back an old topic, but just had one question regarding your Testors engines roddie. Do you happen to know the thread pitch for the needle? I just acquired one over these today with the exact same weird tank assembly and all. However, it had no needle with it, which I missed when making the deal. So i am looking for the proper pitch so i can find a correct size screw and make a needle. Any help would be greatly appreciated.

Surfer_kris Tue Nov 20, 2018 2:47 am

I'm pretty sure it is a UNF 1-72 thread.
I've made new a needle from Brass-stock, it is fairly easy to do using a lathe and the right die for the thread.

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Surfer_kris Tue Nov 20, 2018 2:47 am

Sorry, duplicate...

NEW222 Tue Nov 20, 2018 6:45 am

Thanks for the help. I'll take a peek cause I think I have a screw then. If so, off to the drill press with a file. Poor man's lathe!

Surfer_kris Tue Nov 20, 2018 8:35 am

It needs to fairly long, as the seat is on the other side of the venturi, but otherwise a screw should work just fine.

roddie Tue Nov 20, 2018 7:10 pm

I'm sorry Chancey, I don't know what the thread size is.. but I shot a couple macro images of one of my .049 FRV Wen-Mac/Testors engines' needles with my phone-cam. Maybe they can help you find the answer.

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"measurements below in inches"

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**Cribbs74** Tue Nov 20, 2018 7:20 pm

Pretty sure I have that same engine complete. I don’t like them at all, so it’s yours if you want to pay shipping to Canada. It has the needle.

Ron

ticomareado Tue Nov 20, 2018 7:30 pm

If he doesn't take it, I'll pay the postage to NC.

NEW222 Tue Nov 20, 2018 7:57 pm

Ok. I have since determined by the pictures that the needle is a 1-72 tpi picth thread. I will now look for a screw of the appropriate size and fabricate one. Thank you all for teh help and pictures.

**Cribbs74** Tue Nov 20, 2018 8:13 pm

ticomareado wrote:If he doesn't take it, I'll pay the postage to NC.

Where in NC are you? I ask as I am going to be there after Thanksgiving for work.

ticomareado Wed Nov 21, 2018 4:05 pm

I PMed you several hours ago.

batjac Wed Nov 21, 2018 11:43 pm

Unlike Ron, I actually like these engines a lot. They're not the same quality as a Cox engine, but they're great for what they are. Someday I need to design a twin or three engine plane for these engines. If there was a TEF, I'd be a member there, too.

I applaud trying to make a needle for the valve if you're doing it for the fun of it. But if you just want the engine to run, I'd say just press out the needle valve body and press in a Cox NVA. It actually gets you a more accurate needle setting and a smoother run, from my experience. See the thread I did three years ago:

https://www.coxengineforum.com/t8206-follow-the-bouncing-brain

The Mix N' Match Mark

NEW222 Thu Nov 22, 2018 12:46 am

Thanks Mark. This is both for the fun of it as well as just to run. Replacing the needle is not much of an option here as one would need a needle assembly to do this. However, I appreciate your time and link provided.

Surfer_kris Thu Nov 22, 2018 11:25 am

Here is another picture of my home made one. I made it shorter than the stock and instead included a slot for a screw-driver at the end. It was quite easy to make once I had the correct die for the thread. Always feels good to save an old engine. Smile

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NEW222 Thu Nov 22, 2018 4:18 pm

That is quite a nice needle there. The joys of having, and knowing how to use a lather. I have always wanted one, but.....

ticomareado Thu Nov 22, 2018 4:37 pm

That's just the way Rotomatic starters are made. If you've got a good runner and don't need the nose weight just strip the whole assembly off, drill out a Cox Bee thrust plate, squeeze it on with a plop, plug any rivet hole that might be in the air intake and let her rip. A good one makes a very competitive nostalgia 1/2A F/F engine. A good stripped glow plug model makes for a very light 049 with excellent power to weight ratio.

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Testors/McCoy .049 smoked...