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engine help

Old 12-17-2016, 07:57 AM
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airraptor
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Default engine help

Guys I just paid for this engine but now looking at the picture on the box and the engine in the picture they are different. Anyone have any info if I bought the real thing?

http://www.rcuniverse.com/market/ite...itemId=1093428
Old 12-17-2016, 09:24 AM
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Looks pretty close to me. When you get it, maybe a pic in the back would be nice.
Old 12-17-2016, 07:15 PM
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Ron is either cutting corners from the original or someone cloned the
lable and built one with a modern slit per side exhaust. Stock needle
valve and fabricated their own style engine mount and rear back plate.

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Old 12-17-2016, 07:53 PM
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It looks like two different engines in the photo gallery, since one engine is more red while the one on the box art seems red in both. Mechanically same and different than the box art for sure. If the box art stayed the same since they were first released, then maybe he used different nv assemblies at one point. Just conjecture, I know no facts on RV's engines.

I was thinking a short while ago about how little I know about all the cox cylinder variations, for having owned and messed with them for so long. I know there are some detailed posts, this reminds me to find them.
Old 12-17-2016, 08:09 PM
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Old 12-17-2016, 09:55 PM
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I asked the guy selling about it and he said this is his third engine and they all have that same picture on the box. I did see on another site many other engines posted and it looks close but also looks like so many different one out there. Thing about cox is you can mix and match and not many will know the difference. anyway we will see once I get it. Now do I run it or collect it?
Old 12-17-2016, 11:26 PM
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Should be able to eek out a tad more rpm with a TD cylinder. Being
a rotary valve it is getting a bit more air in vs reed allowing more fuel
so a plus. Tee Bee tested a Drum Rotary engine with his Scalpel.
Also VGE did one.
http://www.rcuniverse.com/forum/1-2-...49-engine.html

Should make for similar power:

https://www.youtube.com/watch?v=H1Z8Evb5TsM

Last edited by Pond Skipper; 12-17-2016 at 11:28 PM.
Old 12-18-2016, 01:26 AM
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I think they were just made in many different versions, perhaps cutting some corners near the end of production with the stock needle valves and running out of non-slit cylinders etc. It certainly looks like the genuine product to me. I only have one of these myself, show below, which I got directly from Ron at the time.

As for running it, you'll have to be careful to avoid wear around the disc. One can easily get galling in that area as there is no Brass or Bronze anywhere. The disc is aluminium, running against the aluminium backplate if I remember correctly.

The location of the pin that rotates the disc is another weak part, as there is very little material for the pin it self. The crank is simply a stock crank while the conrod has been thinned down at the big end to expose a little bit of the crank pin. This gives a rather short pin that sticks into the aluminium disc (less than half of the disc thickness).

I bought mine with the intention of putting an RC carb on it, and using it. But once I saw the construction I came to the conclusion that it is a pretty engine to look at, made for the occasional bench run, but not more.
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Old 12-18-2016, 06:34 AM
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I felt I had to check the engine again to make sure I remembered correctly.
Below are two images in order to illustrate the issue with the short driving pin for the disc. As you can see (I hope) the crank pin is only protruding very little past the conrod, and the crank pin is also chamfered at its end. This gives very little material that can grab the disc, which in turn is made from a very soft material.

I think the design would have needed a new dedicated crank with a longer crank pin, together with a brass disc or a brass counter surface on the backplate, in order to work well.

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Last edited by Mr Cox; 12-18-2016 at 06:36 AM.
Old 12-18-2016, 07:10 AM
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the material selection and finish is sad.
Old 12-18-2016, 07:36 AM
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Controller I am sure back then these were cheap and if it wore out just get another one. Same with cox engines they were so cheap just put a new one in and go. Plus i am sure he was doing the best he could and keeping the cost down. There are ways around this now today where we can make this last forever.
Old 12-18-2016, 04:32 PM
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Pond Skipper. The engine in the Scalpel was a Mangusta DR 049 with a Delrin plastic rear rotary valve. It was built by Tim Wiltse years ago. It wasn't spinning to well in that video. Later on, I was able to get it singing nicely with a different prop or glow head if I recall. Once it was sorted out, it flew the Scalpel with good authority. Unfortunately, the custom machined crankshaft broke at SMALL 2015. That was the end of what was probably the only flying Mangusta DR 049 in the world. I was never able to contact Tim to see if he might have any more of those cranks. I plan to install a TD on the plane soon so I can fly it again.
Old 12-18-2016, 08:43 PM
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Originally Posted by Mr Cox
I felt I had to check the engine again to make sure I remembered correctly.
Below are two images in order to illustrate the issue with the short driving pin for the disc. As you can see (I hope) the crank pin is only protruding very little past the conrod, and the crank pin is also chamfered at its end. This gives very little material that can grab the disc, which in turn is made from a very soft material.

I think the design would have needed a new dedicated crank with a longer crank pin, together with a brass disc or a brass counter surface on the backplate, in order to work well.

Judging by the wear pattern in the disk's crank pin hole, one can see where that the collar like lip on the connecting rod is almost nearly fully seated in the hole. There is some wear at the bottom of the hole from the crank pin. Thus, it seems like it is working as it should.

IMO, there isn't the high mechanical forces on the disk, to warrant it being made of brass, like you would a prop drive plate running a pusher prop. There is some lateral movement from vacuum suction during upward piston movement drawing in the fuel charge from the venturi. On piston downward movement there is a slight positive pressure when fuel charge is transferred from the crankcase chamber to the piston head area.

One would not want the crank pin to be extended as in this design, the connecting rod lip has less movement against the aluminum disk's hole, more of a gentler back and forth motion, than the crank pin, which is rotary. Design seems to be best applied as a tractor, not pusher motor. As a pusher, wonder if that would cause the crank pin to rub alarmingly hard on the disk crank pin hole.

I cannot say though how well this design would wear over time. One would want to ensure that there was sufficient oil in the fuel (at least 20% IMO) to ensure proper lubrication of the disk.

Perhaps due to complications and manufacturing expense of the design is why Cox discontinued the rear rotary valve for the front rotary Tee Dee's and Bee's reed valves.
Old 12-18-2016, 11:48 PM
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Originally Posted by GallopingGhostler
Judging by the wear pattern in the disk's crank pin hole, one can see where that the collar like lip on the connecting rod is almost nearly fully seated in the hole. There is some wear at the bottom of the hole from the crank pin. Thus, it seems like it is working as it should.
This engine has never been run. The pattern in the disc hole is from the machining alone, not sure why they made it oval (shouldn't be needed?). The work in the mill, with a non-flat tip on the tool, gives a protrusion in the center of the hole and the useable depth is about 0.7mm.

If one holds the backplate in place with the crank-pin on the disc, rather than in the its hole, there is gap of about 0.3mm (less than 1/64") between the crankcase and backplate. This would then be the amount of pin that is in side the hole when the engine is assembled correctly. With a chamfer on the pin of 0.10-0.15mm, there is very little left to drive the disk.

One could possibly improve on this a little by shiming in front of the crankweb, I guess, or remove some material on the sealing surface of the backplate (in a lathe). But I wouldn't run it as it is now...

Last edited by Mr Cox; 12-19-2016 at 01:03 AM.
Old 12-23-2016, 02:03 AM
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I took mine appart and made some mods too it. The conrod had not been flattened in the front end, presumably to retain a correct position relative to the piston. I then removed about 0.2mm from the front side of the conrod, this is slightly less then the mod on the backside of the conrod that was already there. With two shims in front of the crankweb the whole crank is shifted back the sae amount and the conrod alignment is retained. I then also had to remove some material from the front end of the crankcase to allow for some play against the propdriver (unmodified). I also removed a little from the very end of the crank pin (still have some of the chamfer there) and now effectively there is about twice the length of pin that can engage in the intake disc, compared to before the mods. It still doesn't look like much perhaps, but it should now be close to the bottom of the alignment hole in the disc. With everything mounted the crank can still move back and fort.

I'm now tempted to run it but will first have to either turn down the heads of the backplate screws, or remove some material from the backplate as there is not enough room for the screw heads at the moment.

The intake seems to very restrictive, there is hardly any room for any air to pass the spray bar...
Should run I guess, but will be throttled down.

Here is a picture of the crank pin after the mods;
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Old 12-23-2016, 07:46 AM
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I got too curious and had to check if it will run...

The piston to cylinder fit is very nice and it fired right up on a port prime. I then ran it very shortly and rich on 25% castor fuel, just to check what will happen. It does make some grey stuff but everything is new so that is not too surprising. Looking carefully around the disk afterwards I cannot see any galling yet, just the grooves from the lathe work. Only time will tell if they will polish out nicely, or if there will be a problem. Should be enough now for the occasional bench run at least. Here are a few pictures taken after the run (open them in a new window for a closer look);
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Last edited by Mr Cox; 12-23-2016 at 07:49 AM.
Old 12-23-2016, 08:08 AM
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Interesting, Mr Cox, you do have an oddity. I can see why Leroy Cox discontinued the earlier 1950's rear rotary valve versions. They were more expensive to make and thus less profitable and less marketable over their other engines.
Old 01-14-2017, 12:27 PM
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R. Valantine makes stuff in small quantities and they differ depending on what parts he started with etc. I'm not familiar with his Cox modified engines though, but those two styles of exhaust ports are common. Looks like his back plate in either case although they are slightly different.
Old 01-15-2017, 01:53 PM
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Originally Posted by GallopingGhostler
Interesting, Mr Cox, you do have an oddity. I can see why Leroy Cox discontinued the earlier 1950's rear rotary valve versions. They were more expensive to make and thus less profitable and less marketable over their other engines.

The mid to late 50s Cox engines you refer to were DRUM valve-not rear disc-known as the RR-1. Cox's terminology was incorrect. The drum was much smaller in diameter (the major rotating mass)-and machined from steel-so the drive flange which engaged the crankpin could be a lot thinner than a disc valve setup-about 1/32" or so-and the drive was via a hole-but a radial slot from the outer edge also works (and is less stringent on alignment. Being hardened steel and ground the material was a lot less prone to galling and wear than the Valentine disc setup-and the RR-1 engine used a shaft with an extended crankpin having a reduced diameter extension. (see second pic) [this was reasonably common practice on some European engines as well-in some cases the drive pin simply pushed into a hollow crankpin-allowing the same shaft to be used for either FR or RD layouts]
Also-being ground-the fits could be a lot closer and more precise than the aluminium disc used in the current breed of Valentine rear rotary valves. Naturally they (the RR-1) were more expensive than the reed valve coxes to produce-and presumably that was why Cox dropped them. A pity really-as I would take an RR-1 over a Babe Bee any day. Some stuff was just silly-the machined ribbed tank and thev ribbed crankcase nose for example-which was purely for appearance-but must have added significantly to the production cost. Likewise the anodised case which though it presents a nice contrast could have been left plain [though I admit the RR-1 is one of the most visually attractive Coxes made-the other IMHO is the Olympic 15] Cox could have achieved the same visual effect simply by anodising a plain machined Bee tank bell blue...and anodising a standard reed valve case yellow for effectively the same visual effect.



ChrisM
'ffkiwi'
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Old 01-15-2017, 03:42 PM
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Nice example. Wow that is a great looking engine! Pricey collectible these days indeed.
Old 01-15-2017, 09:42 PM
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Originally Posted by MJD
Nice example. Wow that is a great looking engine! Pricey collectible these days indeed.

Yeah MJD-I wish I had one myself-but all the good ones are in collections....and the rough ones tend to go for a lot of money on Ebay...

ChrisM
Old 01-16-2017, 06:59 AM
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I passed one by about 4 years ago for $20 because I never saw one before, and did not know what it was. Figured there would be no parts for it if I needed them ...... Oh well, I never seem to sell motors anyway, just look at them in the basement. It is not profitable unless you have thousands, $50 here and there would not pay for the gas to find them.
Old 01-16-2017, 07:50 AM
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A casual search shows them going for $300-500 USD in half decent shape. For that much money, I'll enjoy the nostalgic pictures and play with modern fast .049's..
Old 01-16-2017, 10:06 AM
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Originally Posted by ffkiwi
The mid to late 50s Cox engines you refer to were DRUM valve-not rear disc-known as the RR-1. Cox's terminology was incorrect. The drum was much smaller in diameter (the major rotating mass)-and machined from steel-so the drive flange which engaged the crankpin could be a lot thinner than a disc valve setup-about 1/32" or so-and the drive was via a hole-but a radial slot from the outer edge also works (and is less stringent on alignment.
Chris, would that term "rotary" versus "drum" be more a matter of semantics? Rotary means rotational, and the 1950's were the developing grounds for much more powerful engines than the 1930's and 40's? Did not the current implied meaning of rotary valve develop through de facto buzz words for high performance "racing" versions of glow engines?

Naturally they (the RR-1) were more expensive than the reed valve coxes to produce-and presumably that was why Cox dropped them. A pity really-as I would take an RR-1 over a Babe Bee any day.
I haven't found an engine review, which would help me to compare the RR-1 to the Tee Dee and Medallions. What is its power likened to?

Some stuff was just silly-the machined ribbed tank and thev ribbed crankcase nose for example-which was purely for appearance-but must have added significantly to the production cost.
Back in the 1950's, art deco styling was very common, for example, tube (valve) radios had their cases moulded with this type of ribbed design work. Only speculation, but could it be that Leroy Cox was experimenting to find out what sold engines? Modellers aren't given over to fashion statements but function, so as you allude to, this was a costly step that did not contribute to selling engines.

Likewise the anodised case which though it presents a nice contrast could have been left plain [though I admit the RR-1 is one of the most visually attractive Coxes made-the other IMHO is the Olympic 15]. Cox could have achieved the same visual effect simply by anodising a plain machined Bee tank bell blue...and anodising a standard reed valve case yellow for effectively the same visual effect.
Testors Corp. made a similar costly mistake when they came out with their Black Head series, replacing the Red and Blue Heads. Cast crankcases made a fashion statement but added considerable weight to the engine without significant performance gain. (Adding crank ball bearings would add weight but benefit reducing friction for increased horsepower, but this was not done.) Peter Chinn mentioned with cooling fins, helped create a denser fuel charge, (yet I wonder if he said that to be kind to the promoters). But modellers did not see it that way. Testors continued with cross scavenge technology when others were going to Schneurle porting. One could pick up a Testors Black Head on clearance for $4 or $5 US in the mid 1970's. Nobody wanted them. I bought 5. My brother bought a couple, too. Now, CL fliers use Black Head parts (piston, cylinder liner, etc.) to upgrade the Red Heads (in some cases, machining required) to make a light yet more durable Red Head.

Originally Posted by MJD
A casual search shows them going for $300-500 USD in half decent shape. For that much money, I'll enjoy the nostalgic pictures and play with modern fast .049's..
Or .061's and .074's. I still enjoy playing with sport .049 reedies, they provide a lot of bang for the buck.

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