vh2q

My Feedback: (5)

Using a BW to get my Aspire up into the air. Half the time, it dies after 30 seconds in the air, I think it is too rich?. When it works, it works. Using SIG 25%. Turning needle in until it just screams. Is there a trick to setting the needle? New to Cox motors. Also, has anyone figured out how to mount a folding prop to a Cox? I would much prefer to put this on the nose, I need extra weight up front anyway, and it will glide a lot better.

g-rock

My Feedback: (1)

vh2q,
Are you holding the model with the nose vertical? At least that how I was taught to adjust the needle valve on an 1/2A engine. Can't help you with a folding prop.
Gene

vh2q

My Feedback: (5)

No the plane is a bit big to hold vertical but I will give that a try ... turn it in until the revs peak?

g-rock

My Feedback: (1)

Yes. I think what you were experiencing was a too lean condition. When you tweak your needle valve while holding the model vertical, the engine now will be slightly rich at the beginning of the flight but will lean out at the end of the flight. I am not sure what the proper procedure is when you are using a pressurized fuel tank.

Gene

DeviousDave

They use folding props in F1J, they are usually in the 6-2 size range with aluminum hubs and carbon blades. These are hard to come by, but if you start haunting around in Free Flight circles, someone will be able to direct you to a supplier in eastern europe or russia.

vh2q

My Feedback: (5)

I just tried that technique, it works better. Now I need a bit more fuel capacity to get this thing up higher, it gives me a couple of mins max.

gcb

vh2q,

Did you change the fuel pickup tube inside the tank? The Black Widow is set up from the factory as a control line engine and has the pickup tube on the side of the tank. You should switch it to the bottom for your purposes. That may account for the short runs.

When you take the back off to change the pickup be careful to not pinch or lose the little gasket that fits between the backplate and the venturi.

Good luck. Hope this helps.

George

combatpigg

My Feedback: (3)

If you want more run time, punch a big ol' hole in the side of the Cox tank and run a new line back to a seperate tank. You ruin the Cox tank, but it's useless for RC anyway.
I use Sullivan small silicone tubing and Hayes 2 oz tanks, both available from Tower.
A Black Widow runs for about 15 minutes on 2 ozs.

vh2q

My Feedback: (5)

I would rather use my other Cox 049 (with no tank) and connect it to a custom tank, I was looking at that this afternoon, but then I need to get a new pylon, the pylon I have is specfically designed for a Cox with an integral tank.

Come to think of it, if I am going to make a custom pylon, I need something more compatible with a big and slow glider .... bigger prop with less pitch, lower revs. Any suggestions? I have a vintage Forster 31 here, also a Norvel 61 ...

Well I think I just talked myself into putting an electric in the nose of this thing.

vh2q

My Feedback: (5)

Did you change the fuel pickup tube inside the tank?

Read more: http://www.rcuniverse.com/forum/m_98...#ixzz0tRYsYx00

I just did that, and I found a grass seed sitting behind the reed! And I also realized that the bullet-shaped fairing on the back of the pylon could be converted to an aux gas tank. Just have to put a baffle in there to separate the air passageway from the fuel tank, then connect the aux tank to the main tank from behind somehow. Just drill a hole in the backplate? Or perhaps put a little plastic tank inside the fairing with a hose to the main tank, attached to the upper factory vent/filler. Fill from the bottom vent from now on. It should siphon over, I figure. Interesting!

Question though: I had to remove the reed retainer. When i put it back, it goes two ways. One with the spring finger holding the reed back against the housing (the way I did it); or with the spring finger sitting a small distance away from the reed.

SGC

the crossarm of the retainer should be away from the reed to allow it to open, you can as you said hook an external tank to the top fill line of the BW stunt tank , but you must also block off the other/bottom vent line so it will draw in the fuel from the remote tank.

Andrew

Yup - it won't run as it. Anything touching the center portion of the reed will keep it from sealing and block movement.

hllywdb

Another idea is to run a larger prop, say a 7X3 with a couple extra head gaskets to lower the compression. Should be much more of a fuel miser. I use to run cox medallions with the tank mount that way on 2 meter gliders.

gcb

That's essentially what a Cox Texaco does. Cox included a smaller venturi for additional fuel draw at the lower RPM. They also used a 5-fin glow head to increase heat removal.

I have not tried it, but I would think you should have the extra tank vent pointed into the air stream to supply pressure so it will run off the auxiliary tank first, then the engine's tank. That would mean running a fuel line from the back tank to the front tank vent, then sealing the other front tank vent. Actually, I think someone already said that...oops!

George

vh2q

My Feedback: (5)

I put in a longer fuel pickup, added a head gasket, and with a 6x4 I am now getting reasonable flight time. Had to open up the needle about a turn vs. prior though. Strange. Would like to get more time. Is a 6x3 an improvement over a 6x4 (on the motor right now)? The 6x3 looks like it has a coarser pitch to my eye. I will look around for a 7x3, it will just clear the wing. Seems to me you want a finer pitch, for slower speed? Or is it a coarser pitch, for lower revs?

hllywdb

The 4 is a higher pitch than the 3. It is the theoretical distance traveled durring one revolution of the prop. So a 6X3 would travel 3" forward and a 6X4 would travel 4". The lower revs provide better fuel economy while still moving the plane. There is a point where this drops off, and the plane is also a factor, so a bit of trial and error with different props may be required.

vh2q

My Feedback: (5)

Thanks. Seems to me, for a big slow-moving plane, you would want a finer pitch eg 3 rather than 4. As hlly says, it seems 7x3 is the way to go. The 7" dia may offset the engine's tendency to rev faster with a finer pitch.

R/C Phile

From my experience,


Peaking it on the ground means it's likely to become too lean for max power in the air. When you're holding the plane down, the prop is cavitating / straining and the RPM's are typically lower than they will be in flight.

What I have seen happen is once the plane accelerates to flying speed the RPM's escalate and the fuel demand climbs as well. If it's really peaked to begin with you can end-up with a overly lean setting which causes extra heat and can get to the point of killing the motor if there is not enough oil in the mix. From my experience, the Sig 25% is actually borderline too thin on oil for this kind of condition.

The ultimate setting depends on what fuel you use / prop / cylinder-piston combo / and the plane's drag.

For what we fly, just borderline 4 cycle on the ground is about perfect in the air, as the plane accelerates it clears-out and becomes smooth and steady for the reminder of the flight. This is typically achieved after experimenting over several flights with the equivalent of a "one click" change on a regular R/C carb per flight.

To get there you'd better seal the tank with flight line and seal the carb needle with a piece of tubing per the Gibault mouse racing mods as it makes the needle settings significantly more consistent and makes the fine tuning easier.

I have not seen that type of behavior with the larger engines (.40 +) but for my Cox and Enya 09's that's the only way to safely get max power. An added plus is that once the they are set I rarely have to touch the needle, even over several weeks.

vh2q

My Feedback: (5)

I found it won't run with added castor in the SIG, now that I have added an extra head gasket. It will run great with pure SIG 25%.

Is there a link that explains the "sealing" techniques you refer to?

R/C Phile

Here's a link to the mouse racing program:

http://www.xenalook.com/?id=696654&p...&blogId=117793

Bernie runs that store and he's great to deal with if you need more Cox stuff

The "sealing" part only takes a few minutes and makes a world of difference.

Props wise, the Cox 6X3 works really well for good thrust at the expense of speed. The APC 4.75 X 4 "Combat" and 5 X 3 "Free flight" props would be great to try as well. We got more speed / thrust out of the 4.75 X4 props compared to the Cox 6 X 3 but they are not as durable (Proabably not a concern for you) .

gcb

Since you are using this setup to tow a pretty big glider, I would think an APC 6x2 would work better to let it rev up to slice a lot of air...sorta like low gear. I think the original thinking of a large prop with low pitch would work best for this application.

George

vh2q

My Feedback: (5)

Well thanks to everyone for their suggestions. I "tubed" the needle valve (and in the process of doing so, found a burr on it where some prior owner had screwed it in too hard), altered the pickup tube, added a head gasket, changed the prop to a 6x3, and this evening I had two wonderful flights. Got that glider waaay up there, at least 4 mins of engine time, and then rode some late afternoon thermals for the best glides to date.

I have to say, the only way to get this BW to run dry is to start out very rough, almost not enough power to keep this bird up, but within 15-30 secs she starts to sing and we are off to the races. However, it's now giving me enough run time to get up to at least 400 feet.

Thanks gang!

vh2q

My Feedback: (5)

Well, burned out the glow plug in mid-air (it must have been on its last legs), but with the new plug, it's a new engine! Fires right up without touching the needle, reaches full power right away, and doesn't stop until it's out of fuel!