Cox Venom Piston Rod Reset Question

I got your message.

Let me do some checking before I buy yet another motor.

It may be that removing the tank-extender moved the engine back enough to cause your balance-issue.. especially on a short nose.

One thing you can try is obtaining a heavy hub-nut and use a stub-screw..



A weight comparison to a std. hub-nut..





It might be enough to tip the scale. You could also cut a pair of (.010") brass-sheet squares.. and attach/glue them to the front/tops of the pontoons. How about sourcing a pair of cast "model-ship cleats".. which would look kinda cool.

I think that is a good idea but 6 grams is not going to do it. I have about 1.4 oz in the nose now and I think that is a good starting point. I might be able to remove a little of it later. I will shoo goo it in for now.

BTW.. I LOVE the model! To me; float-planes are the epitome of cool. Just something you don't see modelled "to fly" all that often. I presume that you're hand-launching? I don't think that the Venom has the testicular-fortitude to pull it off the water. Is there any way to incorporate beam-mounting rails through the firewall; that would be below and "clear" the Bee engine? Maybe tying-into the closest bulkhead? This would give you the option of running your Tee Dee's or Norvel by using aluminum bridge-plates for the correct spacing and thrust-line. It would also add somewhat-functional nose-weight to your current construction. You still have the finish-weight to consider too.

I would have to see what ship cleats look like. THat is a new one to me. I am not sure if the floats will change my CG either.

Just did more engine testing. I need to name or stamp these motors to track them.

Black Widow with good compression and rod rest. No tank extension or other mods other than noted below.

Fuel - powermaster 20% nitro, 10% synthetic 10% castor, 2% castor added.
Stock head, 1 shim, 6x3 prop (cox grey) - 13,800
After market head, 3 shims, 6x3 - 14,200
After market head, 3 shims, 4.7x4 - 18,100
After market head, 3 shims, 6x3 - 13,900
Stock Head, 3 shims , 7x4E - 9400
Stock Head, 2 shims , 7x4E - 9500
Stock Head, 1 shims , 7x4E - 9500

roddie wrote:BTW.. I LOVE the model! To me; float-planes are the epitome of cool. Just something you don't see modelled "to fly" all that often. I presume that you're hand-launching? I don't think that the Venom has the testicular-fortitude to pull it off the water. Is there any way to incorporate beam-mounting rails through the firewall; that would be below and "clear" the Bee engine? Maybe tying-into the closest bulkhead? This would give you the option of running your Tee Dee's or Norvel by using aluminum bridge-plates for the correct spacing and thrust-line. It would also add somewhat-functional nose-weight to your current construction. You still have the finish-weight to consider too.

I might do my first launch as hand launch. But I do have undercarriage and I will test with it. if it cannot take off using the main gear from my runway, then there is no way it will pull off the water. I hear you need 20% more power for water take off.

Is the bridge plate thing something I have to fabricate? I have my plane setup with two firewalls. I have one glued in and one that bolts to the other so I can change engines since I am not sure what I want to use to pull this plane. I went crazy buying motors for this thing. As I said, it is sickness. I started with two 049s that I have had for over 20 years but could not find them. So I bought one Babe Bee, then another, then some widows, Tee Dees, why not add in some 09 motors, 020, etc. In two months, I bought over 20 motors. Someone help me!

Thx for the complement.

What you really need is a Norvel .049/.061 Significantly more powerful than a TD, excellent throttle response, muffled and easy to use.

I have one I could trade if you don't want to spend money. Shoot me a PM if interested.

Ron

Landing on the water alone would be fun! I'm assuming that you have a pond nearby.. or near your flying-field. I'd love that! Model boats and amphibious model airplanes!

Assuming that the model will have a water-landing.. it would be good to have a recovery-craft to get it back to shore when the engine quits. A throttled engine would be cool for taxiing back to shore.. and you have a few options there.

roddie wrote:Landing on the water alone would be fun! I'm assuming that you have a pond nearby.. or near your flying-field. I'd love that! Model boats and amphibious model airplanes!

Assuming that the model will have a water-landing.. it would be good to have a recovery-craft to get it back to shore when the engine quits. A throttled engine would be cool for taxiing back to shore.. and you have a few options there.  

My club has two events at a full scale airport that has a large pond on it. I am hoping to bring the Cloud Ranger to the next event and do some H2O flying.

All I need is aileron links and to pad/secure my rx and battery and I will be ready to go. Also need to add rx switch. As it sits with the battery and rx in it plus 1.4oz of nose lead, it is 21oz. I expect to be one oz heavier at flying time.

I have the plane ready to fly. It came in at 21.5 oz without fuel.

I also did an engine test. I am throttling the engine with a needle in the venture. It is an odd thing as you only change air going in, not fuel so it is not proper carburation in my opinion. The BW turns the 6x3 at 14k. The best idle I can get is 8500 as the needle is much smaller than the venture. Also, the mixture is a compromise of sorts. If you set the mixture at full throttle, then the idle, as fast as it is, is not stable. It is very rich. I added 1/8 turn of lean to the needle valve and the high end seems fine with it while the idle is still rich but tolerable.

Anyone else use one of these venture needles from Cox International? Any different experience with them? Am I better off with an exhaust throttle?


Scot

Here is an update. The wind stopped blowing for about 5 minutes today so I took the Cloud Ranger out to the field before it rained. Good news. The Black Widow can pull the plane pretty well. Better than I thought. Throttle response left a lot to be desired but this is just a first test. I had to add 1 oz of lead and I think it might still be tail heavy. With that in mind, I am considering mounting a larger Norvel or perhaps a Queen Bee. The extra power would be welcome when I put floats on it as well. Let me know what you think. I hope to fly it more tomorrow.


https://youtu.be/plIUjD57gkI

It looks to fly pretty well to me even some stunts in there that it seem to pull through just fine (for what it is) , If your tail heavy and thinking about changing the engine for the floats i would go with the Norvel its lighter than the Queen Bee . Good Fun Scot!

Eric
I have quite a few norvels to choose from. At this point, the weight is not a concern since I have 1 oz of lead up there and I think it could use more. The Norvel would be more powerful for sure. When my engine test stand comes in, I will evaluate both options. I might need the extra power for floats too. I think the BW would be difficult in a water environment for many reason. The fact that the idle is not so good is one reason to consider another motor. I have not tried exhaust throttle to see if that is better but again the extra weight is needed anyway so I might as well scale up on the motor.

It may be a couple weeks before I try the next motor out.

Thx

Sorry that was my backwards thinking ? Tail heavy need more weight up front !

Hi Scot, Not a bad 1st flight at all! I've done some bench-tests with that throttle-design (orig. Ace). It's nice to see you try it in flight. Ace recommends using a muffler to keep the top-end "hot" at low-idle. I wouldn't recommend a conventional muffler though.. because it will rob some power. It's a moot-point anyway.. seeing that you're planning a different engine/throttle configuration.

If you ever build a smaller model.. try using that throttle again. I achieved very good throttle response with mine and a much lower idle when using a minimally-restrictive homemade muffler, 6 x 3 prop and 25% Sig fuel. I have found that the engine's needle is best set for optimal rpm with the plunger fully-retracted from the backplate/venturi.

Here's a rather "candid" video I made several years ago..



You'll notice that the glow-driver is "on" throughout the run. I should have turned the driver off.. but neglected to. I have however, achieved similar results with it disconnected. I ran a small 1oz. Sullivan external tank with the feedline plumbed through a hole drilled in the Babe Bee's fuel tank. There are other ways to hold heat in the top-end for a more reliable low-idle.. than using a muffler. A "cowled-in" engine will run hotter.. and some modelers wrap a few turns of string/yarn around the upper cooling-fins when running in freezing weather. Just some things to think about/experiment with.

Roddie
I saw your video about a month back and that is part of the reason I chose to test this configuration.

I agree that the motor needs to be kept hot but I think this design can be improved in the following ways. First, the needle needs to be larger diameter. The diameter of the BW motors venture is such that so much air still enters the motor with the needle in fully. I am not sure why they made the needle so small but it could be so that it would work with other Bee motors with smaller venture systems. If they can create a needle that closes the .07" venture, then I could get the motor to slow down much. Still have a rich problem though. How to fix that? I think one might could fix this by utilizing SPI as a sort of air bleed system. The slower a motor turns with SPI, the more air it should ingest in theory. So start with a cylinder with SPI and close it off with cylinder shims. As you want more leanness on the low end, remove the smaller shims to bleed a little air in. Not saying this is perfect, but I think it would be an improvement over my current config. But like you said, it is moot for the mean time as I need weight up front anyway.

thank you for your input.

Scot

Doing some weight measurements, the 061 novel is still going to require 1oz of lead or more. The 061 with a mount is about the same weight as a Texaco. Also, the 061 requires an external fuel tank. That means my battery will need to be relocated further back. More lead. SO I think the answer is one of the two 074 motors. The QB is 1 oz heavier than the Norvel and I expect the NV to have much more power. I will have to see how each idles and transitions to determine which will be the winner for this plane. If the wing were located 3/4 of an inch further back, the 049 would work fine with no weight. I will keep that in mind if I do a custom build of this fuselage later.

I am still working on the carb for a tee dee too. I am not running pressurized exhaust so I have to do machining on the carb to make it suck fuel when at any throttle setting other than full. I am getting close on it though. The carb has a air intake above the barrel similar to that of a #25 drill bit while the bottom is similar to a #29 bit. I drilled the bottom to #28 then #27. Each was an improvement over the stock config. The idle is still a bit lean if not totally warmed up with the air bleed closed off. I am thinking of just filing the back side of the carb where the idle opening is exposed to let a little more air in. Not sure I want to commit to a #26 bit yet as there is some richness in my mid range that will surely get richer if I open the entire hole up more. The motor is a Tee Dee with a Medallion Cylinder (slotted, no SPI). I am turning a 6x3 grey prop on 20% nitro at 16,400 on my last run. Not racing speeds but not bad power for RC use either.


Take care


Scot

rscarawa wrote:Roddie
I saw your video about a month back and that is part of the reason I chose to test this configuration.

I agree that the motor needs to be kept hot but I think this design can be improved in the following ways.  First, the needle needs to be larger diameter.  The diameter of the BW motors venture is such that so much air still enters the motor with the needle in fully.  I am not sure why they made the needle so small but it could be so that it would work with other Bee motors with smaller venture systems.  If they can create a needle that closes the .07" venture, then I could get the motor to slow down much.  Still have a rich problem though.  How to fix that?  I think one might could fix this by utilizing SPI as a sort of air bleed system.  The slower a motor turns with SPI, the more air it should ingest in theory.  So start with a cylinder with SPI and close it off with cylinder shims.  As you want more leanness on the low end, remove the smaller shims to bleed a little air in.  Not saying this is perfect, but I think it would be an improvement over my current config.  But like you said, it is moot for the mean time as I need weight up front anyway.

thank you for your input.

Scot

Yes.. the BW venturi is approx. .082" as compared to .063" for the Babe Bee/Golden Bee that the Ace/Cooney throttle was actually designed for. The fuel-jet in the integral-tanked engine's backplate is directly inside and above the air-intake.. so with the "Bee's" smaller (.063") opening, there's close-to a 1:1 metering-ratio that can't be achieved with the .082" opening, using this throttle. With the smaller opening, you can actually set and use your throttle-servo "trim" to stop the engine by advancing the plunger into the backplate past the taper.

One of my Golden Bee's actually has the larger .082" venturi.. so I tried grinding a taper on the end of some .078" music-wire to test. It wasn't much of a test, because I hastily threw an engine together.. and the taper that I ground on the throttle-needle was crude. Also; the .078" (5/64") music-wire that I used is .004" smaller than the .082" opening. The design-clearance for the original plunger is .0005"/.001" which will fully-choke the air-intake when fully inserted past the taper. It deserves more testing.. because I believe it can be made to work just as well as the smaller-diameter set-up.

Play with it some more on a rainy-day.. Try swapping the backplate on your BW with a Babe Bee's for a bench-run. Power will be down some.. but I think you'll like the throttle-transition and lower idle-speeds a LOT more than what you've experienced with this throttle thus far.

Take into consideration that; when this throttle-concept was originally conceived/designed.. RC flight-systems were HEAVY. Adding a throttle-servo's weight in addition to the "then available" receiver battery-packs.. loaded into a 1/2A size model, wasn't a recipe for performance. Fast-forward to today.. and there's terrific nano-servos and receiver-batteries that weigh "ounces" less. The power-to-weight ratio of our little Cox glow-engines still rivals the comparable-size brushless-electric motors of today.. except; you get the added realism of having a "real" combustion-engine powering your airplane.

Roddie
I think you have some good observations regarding the venture. Also regarding the advances over time of the radio gear, I agree that the further miniaturization is making these 049 motors a feasible option for small planes. I am surprised that usage of these motors has not picked up more in recent times.

I think I will be building some sort of 1/2a racer next since I have so many of these engines now.

More photos. Floats done minus water rudder. I will need to do a motor upgrade for water takeoff.

https://drive.google.com/open?id=0B_rKS7jwgyK3MkpHN1VzaG13T00

Great work! I was one of the guys that said the Black Widow would have trouble hauling the plane around. You definitely showed me wrong. You have a nice flying plane. I think Roddie is right on with regard to your throttle set up. I hope it flies as well with the floats as it does without them. Nice work!

It was a gamble. I was not sure if the BW would do it. The climb is slow but it does. I am almost 100% sure that the floats will kill it though. Typical rule of thumb is to add 20% more power for float flying. I do not have 20% to spare in this configuration .