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Post  roddie Sun Nov 23, 2014 1:15 pm

I was wondering if there any similarities between Testors and Cox reed-engine cranks? Is there a difference in the stroke-length between the two designs? Are the crank-pins the same size? You can probably guess where I'm going with this.. I'm curious if anyone's spec'd them out, to see if a crank-swap was possible with either engine? A longer stroke might be compensated for by adding cylinder-shims. Could a case be easily bored/bushed for a swap?

Maybe there's just too many dimensional differences?

Any thoughts?


Last edited by roddie on Sun Nov 23, 2014 3:31 pm; edited 1 time in total
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Post  Oldenginerod Sun Nov 23, 2014 3:24 pm

I have both cranks spare so I'll measure them up, but I seem to remember that I have already made the comparison previously and the dimensions were all different. I suspect the stroke will be different because I know the bore size is different, but I'm pretty sure the crank-pins are different diameter.

Rod.
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Post  Ken Cook Sun Nov 23, 2014 5:29 pm

They don't swap out and they're a POS anyway. Testor's cranks looks like they were made with a hatchet. In addition to them constantly breaking.
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Post  GallopingGhostler Mon Nov 24, 2014 9:34 am

@Ken Cook wrote:They don't swap out and they're a POS anyway. Testor's cranks looks like they were made with a hatchet. In addition to them constantly breaking.

I don't recall of them breaking, but then I wasn't a continuous user of them. Perhaps they perform okay as long as one did not abuse them by running excess nitro fuels above 25%, load them up with large props Texaco style or spin them up with too small a prop? Perhaps they are best described as sport engines?
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Post  Cribbs74 Mon Nov 24, 2014 9:57 am

I think Ken described it correctly Very Happy

To each his own though, I certainly wouldn't knock anyone for using them. I imagine in the right application they would work well enough.

Ron

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Post  Ken Cook Mon Nov 24, 2014 10:08 am

Step #1 to finding out if the crank breaks is getting it to run, you certainly may have issues with just getting through that part. Step #2 is removing the broken pieces. Step #3 is acquiring a Cox .049 and never looking back to step #1 Ken
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Post  GallopingGhostler Mon Nov 24, 2014 10:52 am

@Ken Cook wrote:Step #1 to finding out if the crank breaks is getting it to run, you certainly may have issues with just getting through that part. Step #2 is removing the broken pieces. Step #3 is acquiring a Cox .049 and never looking back to step #1 Ken

There is a positive note to the Cox .049 engines (at least the versions other than Estes). I had no problem running them at all. They performed right out of the bubble pack or box, break in was quick, never even gave a thought to problems. They just worked and they would continue to perform. A worn one was easily restored to like new condition. A crash, clean up and they were back in business.

But I still have a place in my heart for the Testors/Wen Macs, OK Cubs and Gilberts. As contankerous as some may be, it is just neat to see another on the field besides the legacy tried-and-true standby doing another successful flight.
We capture a bit of history each time one flies. Leaves
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Post  roddie Mon Nov 24, 2014 12:58 pm

@Ken Cook wrote:          Step #1 to finding out if the crank breaks is getting it to run, you certainly may have issues with just getting through that part. Step #2 is removing the broken pieces. Step #3 is acquiring a Cox .049 and never looking back to step #1 Ken

Laughing.. Ken.. I didn't figure that the two cranks would "swap-out" without some work. It would seem (and probably be a fact) that Testors used a softer spec. steel bar-stock for their crankshafts.. and also did not machine their engine parts to the .0001" tolerances that Cox was achieving.

It's fairly obvious in light of your comments, that a Cox engine wouldn't be the candidate for a swap.. even if it was a "direct" swap. That being said; what if a Testors engine case could be reworked to run a higher quality precision Cox crank? You may ask "why".... but if you had a few Testors engines.. and they all had broken crank-pins.. it might be nice to have an option for getting them to run again.. if all else in the engine was ok.

Granted.. not all modelers are machinists.. and maybe all odds are against permitting a swap.. even in the hands of a skilled craftsman because of differences in stroke, counterweight to piston-weight etc. which would be the major considerations I would imagine. If a Testors crank-pin was a slightly smaller diameter than the Cox pin.. the rod-hole could be resized larger.. or bushed smaller (if their pin is larger). Boring/sleeving/lapping/shimming the Testors case.. who knows? If it were possible.. a standard Cox crank/drive-plate is available through Cox International, for about $10.00 plus shipping.

Yea.. it's a "Pipe-dream".. (pun intended)  Laughing but I'm sure that there's Testors RTF airplanes that outlasted their engines.. unlike Cox; where the engines generally outlasted the airplane.
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Post  ian1954 Mon Nov 24, 2014 3:23 pm

The most difficult parts to machine when making/repairing/restoring a model engine are the crankcase and the crankshaft. The rest is relatively easy.

With the crankcase the "hole" for the crankshaft must be at 90 degrees to the "hole" for the cylinder. The drive pin on the crankshaft (believe me, turning a crankshaft is arduous and I have adjustable offset gadgets for this!) must place the conrod centrally in the "hole for the cylinder. Without this and the drive pin being perfectly formed and parallel with the crankshaft - the engine will not last two minutes.

Conrods are easy and can be mocked up and easily replaced to tune any further misdemeanours. (providing a gudgeon pin has been provided with the piston. The cylinder liner is very easy (including Cox style one piece cylinder/liners) and porting, throw length ...  can be done by trial and error for fine tuning.

I know this is a simplification but I have replaced many crankshafts in crankcases - making them from scratch or using my "parts bin" and modifying the crankcase (or the crankshaft to suit). I am quite fond of procuring busted Thermal Hoppers and modifying the crankcase to accept a standard Bee crankshaft. They run well.

I do however disagree with the "Marketing Hype" from Cox that parts were machined to 0.0001" tolerances. The engines were mass produced and "fits" obtained by trail and error.

The following I cribbed from http://www.mh-aerotools.de/airfoils/cox_album.htm

Testors .049 crankshaft Coxtes10

The piece of equipment in front of Roy Cox was used to check the seal and tolerances of the piston and cylinder.

Pistons were matched by hand into each cylinder and the women were quite adept at judging the proper "feel" of this fit. However, just because it felt right was no guarantee that the piston was truly round. In fact it may be out of round or "clover leafed." So, although it may appear to fit, the piston could still leak compression.

Thus, with this air gauge equipment, which was designed and built in house, pistons were held inside the cylinder and compressed air was then forced into the firing chamber. The piston's ability to maintain the air pressure, as viewed by the air gauge, was the assurance of a proper match. The gauges carried indicators which defined the limits of a acceptable cylinder piston fit.


This is an indicator of excellent quality control rather than machining tolerances.
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Post  GallopingGhostler Mon Nov 24, 2014 11:37 pm

Cox engines of the same type are probably some of the longest running production model engines. As improvements in machinery and techniques occurred over time, would it not be considered that as plant equipment was replaced, that the machining process accuracy also improved over time?

I don't know, may be the Keebler elves still make cookies one by one, hand baked in stone hearthed ovens and all individually hand decorated. Hand Shake
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Post  Ken Cook Tue Nov 25, 2014 4:20 am

George, it would certainly be nice to entertain your thoughts that improvements in quality were made. Unfortunately, that's never true. Cox suffered financially through the years and everyone here on this forum can visually see the changes over the years. Anything that Cox could do to save a step or a person is taken. This all equates to one thing which is money. If that means a compromise in the quality of material be it a lesser grade or plastic, upper management is all for it. We as the consumers are the ones that suffer as a result.   Nothing has changed in the past 50 years. It usually ends up all the same. Fix it until it's broke. Getting back on topic, I can certainly admire anyone who would go to great lengths to make a crank or parts for a Testor's engine. I certainly wouldn't do it myself, but each person has their own little niche I suppose. Ken
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Post  ian1954 Tue Nov 25, 2014 5:29 am

Ken - A hobby is a hobby and for anyone starting out machining it is far better to mess up a Testors engine than say a Cox RR1. My first attempts to manufacture crankshafts and crankcases were disasters. Now, being able to reproduce replacement parts for classics is very rewarding. Still struggling with NVAs though!

George - Cox engines were the epitome of mass production and marketing. They were produced to a price, collectable and usable. I like them all but, as mentioned before, accuracy in production is debatable.

Also there are many manufacturers that began at the same time and are still in production. Enya is a classic - began in 1948 prototyping, 1950 Typhoon 63 (Their first mass produced engine), 1956 Enya 15 diesel (still being produced!) and 2014 - still going! They still make diesels!!!

http://www.enya-engine.com/ListDSL_E.html Drool!

Then we have PAW (More diesels). Started around the same time and still in production. Spares and repairs available for everything. Engine rebores on request along with tune ups!

http://www.eifflaender.com/enginepics.htm Drool! Drool!

I would like to say FOX but I placed and order with them several months ago and got this response

Ian, this is to let you know that the Fox 15 engines are on back order.

In these tough economic times, Fox has had to retrench and focus our limited number of

employees on the outside jobs that provide a profit.

With the price of motors driven by the Chinese imports, Fox engine profitability is limited.

At this time we don't have the ability to dedicate staff to our Fox engine department.

When the economy improves and outside jobs increase, we'll be able to resume engine

production.

Thanks for your support

Fox Mfg.

Sharon


Then again, they don't make diesels. Better a paw than the whole Fox! Laughing

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Post  GallopingGhostler Tue Nov 25, 2014 9:19 am

Ian and Ken, thanks for the replies. Then it makes sense as to why Estes could not pull it off. They would have required the same type of trained expertise to sort through all the left over parts from Cox to make pistons properly fit cylinders. I gather then that is what Bernie and the other sellers of Cox assembled engines then are doing, mating matching pistons and cylinders prior to assembly and sales.
Keebler (Cox) elves are baking and decorating these one at a time, LOL.  Shh
So much for accuracy of 1/10,000 of an inch! Leaves lol!

In a positive sense, I guess then that even so, this grading method took less time than hand lapping assemblies, making Cox more profitable and undercutting sales of others by offering engines cheaper than others could produce them.

It's why ASP/AP engines can be offered cheaper, labor rates in China are considerably less, and import tarriffs have not been adjusted appropriately by our governments. In essence, our governments are funding China's expansion at the cost of our industries. (That is another topic, but I'd rather not us delve into the politics of the issue, although our national leaders, no matter whom have hoodwinked us into believing it is for our own good while our unemployment rate remains high and these governments are now rattling their sabers....) What? No Paranoid
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Post  roddie Tue Nov 25, 2014 1:19 pm

lol! lol! lol! Crying or Very sad Crying or Very sad Sad the only quality left these days.. is in cottage industries.. that have a good reputation for service. Small shops with controlled environments making specialty products. I posted a link on another thread.. It was a Free-Flighter who offered machining services on Cox .020's and also custom parts for other Cox engines. Has anyone here done business with them?

http://www.flyfreeflight.com/Site/Cyl_Piston_Rework.html
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Post  GallopingGhostler Tue Nov 25, 2014 1:37 pm

@ian1954 wrote:I would like to say FOX but I placed and order with them several months ago and got this response:
Ian, this is to let you know that the Fox 15 engines are on back order. In these tough economic times, Fox has had to retrench and focus our limited number of employees on the outside jobs that provide a profit. With the price of motors driven by the Chinese imports, Fox engine profitability is limited. At this time we don't have the ability to dedicate staff to our Fox engine department. When the economy improves and outside jobs increase, we'll be able to resume engine production. Thanks for your support Fox Mfg. Sharon
Then again, they don't make diesels. Better a paw than the whole Fox! Laughing
At this point getting into diesels for me at least would be a whole new venue, which although I'd like to do, just have enough other irons in the fire to occupy my time, figuratively speaking.  Smile

I don't know about others, but it seems that Fox overall is on the decline, too, no telling if they will ever return to production and sales. Tired w/ Coffee Read
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Post  roddie Tue Nov 25, 2014 4:00 pm

Hey George, I'd love to get into dieselizing a Cox reedy! Just for the sake of trying it. What's the investment.. $30..? Build a nice little profile stunter for it... Might be interesting to run a 7+ inch prop on a say; a 1/2A Nobler.. converted to a radial engine-mount. A little too much airplane for a Bee on glow ignition.. but a diesel would be a nice slow-steady "puller" when compared to running a screaming Tee Dee. Shocked
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