lildiesel

Anything you folks can tell me about the care and feeding of these? I just picked up a couple of sets for some parts I wouldn't ever fly again and wonder how they will perform. I'm thinking about slightly underpowered single-channel flying. Will these be in the ballpark? Every Cox I've ever met has had two by-pass ports... Will I still need a shim under the cylinder to tame them or just an extra head gasket?

Having fun in CoxWonderland and need some guidance from the Whizards.

icerinkdad

You have become the proud owner of the original cylinders used by Cox for the Baby Bee engine. They work fairly well, give somewhat better mileage, at the tradeoff of maybe 3000-5000 RPM less on the same props than the dual by-pass cylinders used in the later Cox engines. Give it a try. Worst that happens is you need to trade out for dual by-pass later if there isnt enough power. Otherwise care and feeding is like any other Cox.
Bob

lildiesel

Sounds great to me, given my Clark Kent pilot persona. A mild Bee will go great in a Laumer design in the Spring if my Cub B isn't running right. A Button is on the board right now for .020 or the glow OK.)

dckrsn

For reference purposes-
The single bypass cylinders are #2 and #8.
#2 has sub port induction, and #8 does not.
As far as I know, neither had the top fin milled
for a wrench. Looks cool.
Fwiw, #2 is one of my favorites.

Bob

lildiesel

Great stuff! Just the info I need. I've apparently got a couple of #2s, but when I turn over both on a crankcase I have on my desk, one cylinder shows a lot more SPI than the other. Must be from different production runs. Both have good piston fit and compression, so the "Mild Bee"s I want to put together ought to work with the Cox cylinder shims to make them non SPI and lower the compression a bit. Great stuff for a Laumer single channel bird or some really retro control line ship.

gcb

My first NEW engine was a Cox Space Bug Junior. It had a single bypass port and a smaller venturi, compared to the Space Bug. Together these provided an easy to start engine with great fuel draw. I used it in various Scientific models with excellent results.

Later "sport" engines like the Babe Bee, Golden Bee, Medallion, etc. used a single bypass. The idea is to offset great performance with easy handling. Product engines were originally single bypass but since they needed more power to get those HEAVY RTF's off the ground, Cox switched to two bypass ports. Later Cox engines became somewhat mix and match, plus if you got it used, substitute parts may not match the original. BTW, Babe Bees were used as the ORIGINAL product engines.

Using single bypass cylinders in engines intended for dual bypass should work but fuel draw, and the ability to pull larger props may suffer. Remember that intake size and bypass area were matched to move a certain amount of air and fuel. Give it a try. If it works for your installation, great. Otherwise, you may need to do some swapping. What engine do you intend to use them in?

George

gcb

SPI will not hurt the engine run unless you are running a muffler or exhaust throttle. Remember when you raise the cylinder with those shims, you are also changing the intake and exhaust port timing. This MAY lead to the engine being unable to handle large (6") props.

Experiment around but don't be surprised if the best performance is found by just swapping cylinders and use one shim at the plug and one under the cylinder.

George

lildiesel

I've got a couple of complete crankcase units that just look empty and forlorn on my bench. I'm just putting together some stuff to fly at the nearest baseball diamond on 40' or shorter lines. Lazy 8s and wingovers will be the extent of the aerobatics. Delrin backplates and 5/8th oz wedge tank for the rest of the set up. I've also got some cool looking collector rings/exhaust stubs that will go on them on flying days shimmed up for no SPI. They don't really muffle anything but they can be a good get out of jail free card if somebody objects to the sound of a Cox .049 in the early morning...

[quote]ORIGINAL: gcb

Red Bearings

In the past I flew a lot with 2 TDs. I set them up with sub piston induction single bypass cyllinders, low compression heads, Tarno carbs, cox muffler
I got the Tarno carbs from a fellow club member who could not get them to idle.
I made 2 discoverys, no muffler NO IDLE, no spi NO IDLE. with both spi and the muffler the engines would idle for ever.
I flew a 3 channel QT and a Piece of Cake with a slightly lengthened nose, I made a metal tank so I could use Diesel fuel more easily.
Both aircraft were flow a lot on both glow and Davis Diesel.
I used an old nylon 6/3 propeller and set the needle valve slightly less than full peak.

lildiesel

Thanks for all the info. It's finally Spring Break and if the weather is good I'll get the engines mounted on a piece of 1x2 and clamp that in my B&D Workmate. In a long afternoon I can try all the things suggested here and see what I've got. One for glow and the other with an RJL diesel head.

jeffie8696

Just as an aside. I just picked up some new Testors/McCoy .049 parts and I find they all have twin bypass cylinders. I never really noticed before. I will need to test them to see if they are as good as the original ones that came on my 2 original .049 Testors engines.

I used 2 to rebuild my engines (cylinders, pistons, glow heads) and I think I will sell the rest.