Cox 049 RPM ???
11-27-2012, 05:52 PM
#101
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RE: Cox 049 RPM ???
Here's one with a power to weight ratio that makes the Gilbert look like a killer.
I have a homemade marine glow engine that came in a small Chris Craft scale model. It's quaint and funny to me, a half-A with machined brass crankcase and lower cylinder, looks like a Fox .07 cylinder threaded onto a machine shop student's brass hash pipe. Has a flywheel, not a normal thrust washer, so tough to fit a prop for bench running, but maybe I will persevere and try that sometime. Coaxed a few half-hearted pops out of it on the flywheel. Not sure if it is capable of sustained running actually.
I wonder if it is from a plan, maybe an old boat modeller magazine do-it-yourself project? Anyhow I digress from the thread but it is 1/2A.
I have a homemade marine glow engine that came in a small Chris Craft scale model. It's quaint and funny to me, a half-A with machined brass crankcase and lower cylinder, looks like a Fox .07 cylinder threaded onto a machine shop student's brass hash pipe. Has a flywheel, not a normal thrust washer, so tough to fit a prop for bench running, but maybe I will persevere and try that sometime. Coaxed a few half-hearted pops out of it on the flywheel. Not sure if it is capable of sustained running actually.
I wonder if it is from a plan, maybe an old boat modeller magazine do-it-yourself project? Anyhow I digress from the thread but it is 1/2A.
11-27-2012, 08:03 PM
#104
RE: Cox 049 RPM ???
ORIGINAL: ffkiwi George-I'm pleased to play fairy godmother this morning [it was either that or get driven mad by all the 'Hobbit' movie premiere hype from all the various media!....yes the world premiere is here today-starting at 7pm. The whole damn city has gone half mad..........]
Anyway-following on from my comments yesterday I've done some test running of the Gilbert 074 this morning (its a lovely spring morning-and no boots or heavy objects have come sailing over the fence yet-so it seems I haven't annoyed the neighbours enough yet....................)
I note for your interest (and anyone else's who may be interested) the following points: (fuel was 15% nitro-20%castor-this mix was chosen so it was as close to your fuel as possible.It was pretty old fuel though-so figures might be improved on a fresh batch!)
(1) The engine starts very easily by hand. Unfortunately-in common with reed valves and other sideports-it starts backwards just as often as forwards. It is noticeably slower backwards-not unexpectedly, as there is no thrust washer or any means of absorbing the crankshaft end loading when running backwards.
I note for your interest (and anyone else's who may be interested) the following points: (fuel was 15% nitro-20%castor-this mix was chosen so it was as close to your fuel as possible.It was pretty old fuel though-so figures might be improved on a fresh batch!)
(1) The engine starts very easily by hand. Unfortunately-in common with reed valves and other sideports-it starts backwards just as often as forwards. It is noticeably slower backwards-not unexpectedly, as there is no thrust washer or any means of absorbing the crankshaft end loading when running backwards.
(2) My original 'conical' head let me down once again-and would not run without the battery connected-even though the element showed a good healthy glow. It ran a struggling 6000+rpm on the 7x4. I changed to one of the 'truncated trumpet' heads and had no further problems.
(3) Needle setting on the large props I found to be critical-a click either way on the ratchet and revs fell right off. This characteristic disappeared on the 6'' and smaller props.
(4) The engine is prone to vibration if there is the slightest prop imbalance or poor prop centre-ing.
(5) The engine runs very hot-despite the 'rattling good fit' of the crankshaft.........
(6) Starting was pretty much the same hot or cold (ie it didn't deteriorate when the engine got hot
(7) The engine stops easily with a brief touch of the finger to the intake-I did the whole test on about three 10cc tanks, stopping part way through each tank to change props
results: Taipan 7x4 white nylon 9,200rpm
APC 7x3 rigid 11,300rpm
APC 7x3 rigid 11,300rpm
Cox 7x3-1/3 black 10,400rpm
Master 7x3 rigid 12,100rpm
Master 6.5x3.5 10.800rpm
APC 6x3 rigid 15,200rpm
Master 7x3 rigid 12,100rpm
Master 6.5x3.5 10.800rpm
APC 6x3 rigid 15,200rpm
Cox 6x4 grey 14,300rpm
Cox 6x3 grey 15,600rpm
Tornado 5-1/2x3 nylon 16,800rpm
These figures show that the engine is not the dog a lot of people think it is-but it is clearly not too good on bigger props-6x4-6x3 and perhaps the APC and Master 7x3 sizes seem to be about the best.
Cox 6x3 grey 15,600rpm
Tornado 5-1/2x3 nylon 16,800rpm
These figures show that the engine is not the dog a lot of people think it is-but it is clearly not too good on bigger props-6x4-6x3 and perhaps the APC and Master 7x3 sizes seem to be about the best.
The engine ran particular well around the 14,000-15,000 mark and was easy to set at that rev band. I think Peter Chinn was right-potentially the 07 would run up to close to 20,000rpm on a small prop-the Tornado needed more attention to balance and centreing-so most of these figures might be improved upon.
I think providing it is used in 049-06 sized C/L models it will be adequate-it is certainly no Norvel!
The hot running concerns me though-I don't know how the engine would handle runs of 5-10 mins in C/L or R/C models-and if this hot running was typical-then I can see there might have been problems when installed in the moulded plastic RTF C/L models it was made for-potentially melting the cowl mouldings or distorting the engine mounts.
11-27-2012, 08:17 PM
#105
RE: Cox 049 RPM ???
ORIGINAL: MJD If anybody is all excited about one of these engines now, check it out: [link=http://www.ebay.ca/itm/EXCELLENT-VINTAGE-GILBERT-11-GAS-MODEL-AIRCRAFT-ENGINE-/271109595077?pt=US_Character_Radio_Control_Toys&hash=item3f1f641fc5&_uhb=1#ht_500wt_1414]Gilbert .11[/link]
Come to think of it, with lighter weight equivalent power from Cox Sure Starts, some of the colorful offerings from Cox International and a few others, I've already got a Gilbert .07 and .11, I bought them since I had a love for the older technology and was also just curious. With that and the modern Norvel .074, Thunder Tiger .07 available with the power of the .11 and the Coxes at the power of the .074, unless one is collecting, for the money, having one copy is enough for me. (Unless something is ridiculously priced cheap.)
11-28-2012, 04:46 AM
#106
RE: Cox 049 RPM ???
ORIGINAL: GallopingGhostler
... I'm thinking about putting the Glibert .074 in a 1/2-A CL profile plane. Now I understand why Scientific's 1/2-A's designed by Walt Musciano and a few others would specify ''.020 to .074'' in their 18'' (460 mm) wingspan CL designs. Prior to having this engine, I thought an .074 would have been an overkill.
... I'm thinking about putting the Glibert .074 in a 1/2-A CL profile plane. Now I understand why Scientific's 1/2-A's designed by Walt Musciano and a few others would specify ''.020 to .074'' in their 18'' (460 mm) wingspan CL designs. Prior to having this engine, I thought an .074 would have been an overkill.
When you consider an old kit you must take the power available in engines during their design period. A NV or NORVEL .074 puts out as much power as a .15 of that period. Some engines in addition to .049-.051's of the early/mid fifties were K&B Infant (.020), Spitzy (.045), Royal Spitfire (.065), and Cub .074. In the mid/late fifties Cox brought out the PeeWee (.020).
There were lots of performance improvements in the fifties/sixties in engines of all sizes.
AC Gilbert never had much of a chance because shortly after the engines came out the company went belly up. Still, they were intended as beginner engines thus the uncommon sizes. I got mine from a sell-off at Polk's. A couple still had plastic screwed to the mounting holes where they had been ripped out of RTF's. A couple of the .07's had a starter spring arrangement and a pusher prop. These were from a kite type airframe with a pusher prop. Some came unassembled in plastic bags...two with unfinished crankshafts that, unless I do a final fit, will not go in the crankcases.
I got my Gilbert .11 from a yard sale. It is missing the thrust washer, prop washer, and prop nut. I borrowed some from a Fox .15X to run the Gilbert .11.
For a few bucks in a sell-off I did not expect much. I fit engines into planes that they can handle.
None of my Gilberts were hard starting but I have not extensively run any of them...just break-in.
George
11-28-2012, 05:01 AM
#107
RE: Cox 049 RPM ???
Thanks for the bit of history and sharing your engine collection, George. Yes, although the Gilbert was a later entry, I was thinking of Walt Musciano's design being based on the engine technology of the time. These included the lesser efficient available technologies. Then came dramatic improvements in performance with Glenn Cox's offerings, and of course the follow ons with modern porting and ABC/ABN technologies, which improved the break in process.
They kind of remind me of the Russian older 1950's tech cameras that were being sold by Porter's camera store into the 1990's, a little rough but functional.
Well, I did find out that the humble older technology Gilbert .074 can perform, now looking for a stubby nosed sufficient wing area profile 1/2-A CL it can grace, something from the 1950's.
They kind of remind me of the Russian older 1950's tech cameras that were being sold by Porter's camera store into the 1990's, a little rough but functional.
Well, I did find out that the humble older technology Gilbert .074 can perform, now looking for a stubby nosed sufficient wing area profile 1/2-A CL it can grace, something from the 1950's.
11-28-2012, 05:05 AM
#108
RE: Cox 049 RPM ???
ORIGINAL: GallopingGhostler
Wants $21 US for shipping, a little steep for me.
Wants $21 US for shipping, a little steep for me.
Good luck.
George
11-28-2012, 06:14 AM
#109
RE: Cox 049 RPM ???
Thanks George, but for the moment I'm content with what I've got. BTW, now looking at a couple 1940's, 1950's stubby nosed half-A profile CL plans to put the Gilbert .074 in. Keith Laumer's Gee Bee Z might be a good fit.
11-30-2012, 03:49 PM
#112
RE: Cox 049 RPM ???
ORIGINAL: klord125
Combat what are you getting for RPM's out of your SWR in the video? That thing sure sounds like its twisting them up..
Combat what are you getting for RPM's out of your SWR in the video? That thing sure sounds like its twisting them up..
Regardless, this gives a ballpark idea of what the TD is capable of on low nitro.
IIRC...Jeremy Chinn [Matchlessaero] clocked a full wave piped TD at 123 mph on one of his designs. So AFAIK...he holds the absolute TD .049 RC speed record on a plane he called "Caliente". I believe he used a 4 pitch prop to do that..so his run would have required 32,500 RPM...!
11-30-2012, 04:42 PM
#114
RE: Cox 049 RPM ???
MJD...your ears are surely better than mine. I've got 74 db of permanent ringing in these ears that hearing aides have a hard time competing with.....[:@]
A "GOOD" TD should be able to run at 24,000 rpm with a 5x3 prop on 40% nitro...that will always be my standard reference. I'm not sure what a good TD should be able to hit on 10% nitro [static] with a 4.2x4...since all my TDs are worn out / patched together from the good old days of 1/2A Combat. None of mine have any "POP" like they used to. Thank God for the electric starters.
A "GOOD" TD should be able to run at 24,000 rpm with a 5x3 prop on 40% nitro...that will always be my standard reference. I'm not sure what a good TD should be able to hit on 10% nitro [static] with a 4.2x4...since all my TDs are worn out / patched together from the good old days of 1/2A Combat. None of mine have any "POP" like they used to. Thank God for the electric starters.
06-06-2021, 03:48 PM
#115
I was looking for good numbers on a Nylon Cox 6X3 with a Sure Start and this thread came up; it has lots of information of interest, so I'm bringing it to the forefront since it seemed so difficult to find again -
13,000 seems a baseline for this type stock reed valve with this size prop and 25% nitro if I understand correctly -
13,000 seems a baseline for this type stock reed valve with this size prop and 25% nitro if I understand correctly -
Last edited by H5606; 06-06-2021 at 03:58 PM. Reason: specifics
06-20-2021, 12:13 PM
#116
I have no idea if a Killer Bee is an original Cox product or not -
Anybody have experience with or know if the Killer Bee will actually turn bigger props like a 6x3 at higher RPMs than other Cox reedies?
Also, is a Killer Bee backplate any different (in terms of performance & excluding color) than a stock product or Surestart engine backplate?
Thanks for any help here -
Anybody have experience with or know if the Killer Bee will actually turn bigger props like a 6x3 at higher RPMs than other Cox reedies?
Also, is a Killer Bee backplate any different (in terms of performance & excluding color) than a stock product or Surestart engine backplate?
Thanks for any help here -
Last edited by H5606; 06-20-2021 at 04:12 PM. Reason: Add'l question
06-21-2021, 10:51 AM
#117
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"As I understand it" only owning a recent version and never having run it on larger than a 5-3:
There are the original Killer Bee then the Estes version. The original had crank web and other mods and TD cylinder. The recent version has a regular Bee crank and then-current TD cylinder. They both have an enlarged venturi, but the backplate is the same basic molding.
IMHO: a larger venturi in itself doesn't necessarily improve lower rpm performance. The other mods may bump rpm. I would expect it to come alive on smaller props and a bit stronger than a Sure Start on larger. I could be more helpful if I dug it out and fired it up on the stand.
There are the original Killer Bee then the Estes version. The original had crank web and other mods and TD cylinder. The recent version has a regular Bee crank and then-current TD cylinder. They both have an enlarged venturi, but the backplate is the same basic molding.
IMHO: a larger venturi in itself doesn't necessarily improve lower rpm performance. The other mods may bump rpm. I would expect it to come alive on smaller props and a bit stronger than a Sure Start on larger. I could be more helpful if I dug it out and fired it up on the stand.
