combatpigg

My Feedback: (3)

I don't believe in spending a lot of time bench running. Just get it to where it will run through a full tank at a constant needle setting, then go out and have fun with it. Unless you've got a full service machine shop and prototype facility, there isn't much you can do beyond keeping things clean, tight and properly adjusted.

lildiesel

I'd appreciate a PM too.

As for the SureStart with the restrictor ring, ditch that and try to find a RC Golden Bee cylinder, ring, and piston. I think even a fairly well used one would run better than the SureStart.

Andrew

Done!

andrew

trike_flyer

Hi guys

Took my plane out tonight and the low test fuel I have, low test is ~18% nitro fuel.  The temp was about 11 deg celcius.  It ran weak and I had to get out my high test, ~25% nitro, to get it to fly.  Has anyone had trouble with low nitro fuel in the 049's and cool temps?

R/C Phile

WIth a Cox 049, low nitro will give you low power at any temperature. In fact, low temps (Up to a point) should give you more power as the air is denser and engine cooling is improved (You can get away with a little leaner mixture). For those little guys 25% is good and 30% nitro is even better as it makes for easy starts, more power, and a less sensitive needle.

If I remember right, the Cox "Basic" sport fuel was 25% nitro and the "racing" fuel was 35% Nitro.

MJD

My Feedback: (1)

The lowest a regular ol' Cox .049 likes to run on is 15%. They run much more happily on 25%, but they "should" needle fine on 15%. I don't recall having much cold weather trouble on 15%, but the proof is in the pudding, if your performs better on the 25% then that is the answer. When you get to .020's and especially .010's, 25% - 35%.

What is this 18% fuel you have?

Mr Cox

I'm regularly running engines on 10% nitro and 20% all castor. Temps around 10°C is nothing strange or uncommon here, it is when it approaches freezing that the castor becomes thick and the first start from a cold engine can be a bit tricky.

I haven't ran any Babe bees for quite some time, but I run an 05RC regularly on 10% nitro and it makes about 17000rpm on a 6x3 graupner prop (and idles down to around 4500 IIRC). This is on pair with the AP Wasp .061 on the same fuel and prop. It may well run better on more nitro but it is not a problem to run with 10%, to me.

gcb

I have used 5% nitro successfully, but I like at least 10% because it needles better.
There are a few things you may want to consider if running low nitro. These are only one opinion, and you may get different results:
The engine needs to be in an airplane that does not require every RPM you can wring out.
For a given fuel and prop, compression should be adjusted (plugs, head shims) to obtain maximum power for that combo.

George

tru168

Hi,

I'm flying sport plane, and I'm using homebrew 0% nitro, with 2% acetone without any problem in my Cox production series 049 engine. Master Air Screw 6X3, at 13000 rpm , it sounds / read constant and smooth.
I will order a surestart and see if newer sure start can run smoothly using 0% nitro fuel/

combatpigg

My Feedback: (3)

That's really good power..! I've never tried Acetone, what is the idea behind doing that..?

Here is a Cox TD .049 on either 10 or 12% nitro...it sounds pretty happy out there.[link]http://youtu.be/uILmkzA4M5Q[/link]

tru168

Hi,

The acetone already pre-mixed into the methanol when I purchased it. People believe that acetone will help the engine run smooth and more constant output. I asked the person who give me a gallon of industrial methanol. He said by adding 2 % of acetone, the methanol will absorb much less moisture / water in the air, and good for long storage.

Andrew

I've read that it improves ignition, which might help with needling. The downside is that acetone is so volatile that the container needs to be sealed tightly at all times except for drawing out fuel. I'm not sure how effective it would be with blocking water absorption - that might just be a by-product of a maintaining a sealed container.

combatpigg

My Feedback: (3)

Thanks for the explanation.!
Here is another happy run by a TD .049 on 10-12% nitro.[link]http://youtu.be/Yy_JM4T-yrQ[/link]
The engine has a lightened piston, a KK needle and a Nelson head.

klord125

Combat that thingreally hauls the mail !!!! I like it !!!!

combatpigg

My Feedback: (3)

Thanks..! It shows what a Cox TD [or a KillerBee] can do when mounted onto $15 worth of wood.
TD .049s are still really plentifull and cheap. A lot of old folks still have them laying around in attics and closets. A RC club member could put out an "APB" for all members to surrender their TDs that haven't seen the light of day since Nixon was in office and pay a reasonable bounty for them.
There's still enough of them sitting around for a RC club to decide to build a bunch of balsa sheet racers and have some low cost fun pylon racing on a 300 foot, 2 pole or 3 pole course.
A group build could be done in 5 or 6 "two beer" sessions.

klord125

I think I may have a couple around some where?? The search will begin.lol Combat do you have any plans for that SWR? if so are you interested in selling a copy? Thanks Ken

MJD

My Feedback: (1)

Read through this thread for some ideas:

[link=http://www.rcuniverse.com/forum/fb.asp?m=10699793]SWR chatter[/link]

combatpigg

My Feedback: (3)

Klord, this sketch has the critical measurements to get you in the ballpark. I don't recall what the V-tail angle is, probably 115 to 120 degrees.
I use really light 1/4" balsa for the wing and inlay 1/4" x 3/16" spruce or basswood for the spar.The spar extends about 2/3rds the way into each wing panel.
I use 1/64" plywood doublers inside 1/8" balsa fuselage sides and use 1/4" plywood for the firewall and mount the engine with #2 sheetmetal screws.
I make sure the wing is anchored good. Inbed 3/4" birch dowels in the wing to support the #8 sheetmetal screws and set 3/16 plywood plates in the fuselage mounted to hardwood supports. The sheetmetal screw threads hold up, but hit the wood with thin CA to harden the threads in the wood.
I ran out of "aileron horn brackets" for this plane, so I took servo arms and cross drilled them with 2-56 threads. So now, I basically have a lifetime supply of those parts that I used to drive an hour to buy..

tru168

Hi all,

Just wish to update with my test on old cox production series with homebrew 0% nitro fuel.

I checked all parts after several test run, and here's what I do :

clean all parts inside out, cut a new reed from old floopy disk, ( the original mylar reed looks curled a bit ) reset loose piston joint and oiled. re-check prop balance. with my same old 0% nitro fuel and 6X3 Windsor prop, I run it rich for 3 minutes and lean out for 1 minutes, cut the fuel and refill the 1oz tank, and start it at its peak for 2 minutes and tech it , I got 13,400 rpm.
standard cylinder with 2 bypass port, no booster port and no SPI, I'm really happy with the result. I don't have any others good working Cox engine to compare with, but I think maybe old style cylinder without booster ports seems to design to work well with 0% nitro fuel ??
I'm still looking for a good throttle muffler to test with it, but still can't find one. I did found a few used or new throttle muffler previously but I gave up because of too expensive for me, some need to have ground cylinder to fix , not suitable for me. ( Anyone of you willing to sell to me a throttle muffler at cheap price please PM me ;-) )
I will try 5X3 prop later and see how it perform .

Edit: 5X3 cox rubber duckie tested, 15,700 rpm. not as smooth as 6X3 . ( again , 0% nitro fuel ) calculated power output for 6X3 at 13,400 is around 46 watts, but 5X3 at 15,700 is 36 watts. This Cox don't like small prop. Try on APC 7X3, too heavy, not suitable, 11,700 rpm, but engine heat up fast , and performance drop within minutes. I will try wooden prop if I can find one. APC 6X2 seems suitable, 16,000 rpm.

GallopingGhostler

Reading this thread about Q-Tee and Cox engine caught my attention.

Regarding the Q-Tee with its generous wing area, was surprised that a true Cox (not Estes) Black Widow on Sig 25% with Castor would fly decently at a 6,500 feet (1,981 m) elevation with a Master Airscrew 6x3 prop. It barely lumbered along hardly maintaining altitude with a 5x4 prop. I don't have a tach and never calculated Watts, but the bigger disk for thrust worked. At sea level, either prop seemed to pull the plane at about the same speed.

I picked up 2 Sure Starts for a song when Estes was liquidating them prior to Cox International Canada nearly buying all their parts. Warren Leadbeatter, a Cox guru posting an interesting hop-up article for this engine on E-Bay, [link=http://reviews.ebay.com/Cox-Surestart-Hop-up?ugid=10000000005390559]eBay Guides - Cox Surestart Hop up[/link]

Article mentions removing screen, temporarily removing the needle valve and spray bar, drilling out the venturi in the engine back, change plug with sufficient head gaskets to improve performance.

GallopingGhostler

I also just wanted to mention, Warren also has an excellent article on the Cox engine line:

[link=http://reviews.ebay.com/Cox-Model-Airplane-Engines?ugid=10000000005364876]Cox Model Airplane Engines : eBay Guides[/link]

It includes the history as well as differentiating the different .049 cylinder portings through time.

He is a moderator in Yahoo Group [link=http://groups.yahoo.com/group/049Collectors/]049Collectors[/link]

Warren has quite a collection of .049's of all makes including other small engines. It is worthwhile browsing the pictures and file sections. It may be worthwhile for those who are interested in finding answers to befriend that group. Larry Ranger, former Cox engine employee and designer (I think) posts there. Bernie, owner of Cox International Canada occasionally posts there. They will discuss all small engines, not just .049's.

Also just wanted to mention, regarding comments about E-Bay and exorbitant prices on the Sure Starts. For a time, they were going for only $7 US at Estes Cox Engines website. There were some speculators who were profiting from buying these and selling them on E-Bay for considerably more. IMO, Estes was liquidating the engines, probably selling the below cost to reduce inventory.

I gather that Bernie's products have rebounded the quality and consistency that was lacking when Estes was selling engines. Costs are up but his prices seem reasonable. This is not bad for an engine line that carries 70 years of legacy.

combatpigg

My Feedback: (3)

Besides opening up the air passages I think shaving the insides of the piston skirt and choosing the lightest possible props are other important "mods". Raising the skirt to unveil .010" SPI helps breathing and it also lightens the piston some more. I've never needed to rebalance after doing this.
Detailing the fit of the crankshaft to the case really isn't a mod, but it is a neccessity. The KillerBee relieves the fit in the middle of the shaft and leaves just the extreme ends of the shaft tight enough to provide the slop free fit with the engine case. A flick of the prop on just the bottom end assy should set the prop moving for quite a few revs.
You want a zero slop fit at the ball socket.
Joe Klaus used to advocate a tiny amount of slop, but zero works better for me.

GallopingGhostler

There's also a couple hundred RPM loss through that spring ratchet starter on Cox's from the .049 R/C Bee on. I prefer the older snap back spring starter that was used since the 1960's.

klord125

MJD and combatpig.. Thank you for the information.

combatpigg

My Feedback: (3)

Glad to be of help Klord. Hope to see you build your version of this plane.
The Vtail is a PIA to get concealed linkages ...so unless you are pretty experienced or just love to tinker.....a conventional tail works just as well.