Eldher

I would be inclined to say it is a harmonic. With the 2 engine's pistons aligned in the horizontal position it seems quite possible. But I am just guessing here. An interesting physics problem!

For my 25 with glow engines I have onboard glow, which is set to turn the glow is ON whenever the RPM of *either* engine drops below 1500 RPM. I don't want that glow plug to cool off on final approach with 4 cycle engines and low RPM. Of course this makes starting easier as the glow power is ON from the initial start util I takeoff (minus engine run-up).

Eldher

Nice video. That OV-10 sure floated with the engines out, nice power off landing. While I've not flown the 25 "power off" me thinks she is more like a rock than a glider!

Eldher

Guys, in case you are interested, I have started construction on a 105" A-26 Invader. This is a full build project. If you're interested in following along, I've got a build thread here:
http://www.rcuniverse.com/forum/rc-w...l#post11909884

kiwibandit

Harmonics it is. I changed the blades to a pair of 16x8 apc. Mounted one in line with the crank and one at 90 degrees. The one at 90 continued to run so both were set at 90. Hmmmm. Now both engines will idle and run up together quite well. I'm also going to change the engine mounts. I used the Hanger 9 metal type as they are easily adjustable. This may be a big part of the problem. They transmit all the engine noise into the airframe. I'll try the mounts that came in the kit and see if there is any improvement. I'll also loose the steel rod for the throttles. I will need to do this anyway with my spark conversion. Maybe a Sullivan or similar to replace them. It has put the brakes on the desire to get her up into the air. My flying buddies are all saying "just fly it" but i would like her to have the best chance of surviving I can. My resolution now is It will fly when it's ready. Stuff what everyone else feels. It's not their money or effort on the line.
Testing times ahead I feel.

The Kiwi Bandit.

Eldher

I applaud you on you attitude Kiwi and your willingness to ignore the guys at the field! Fly when the plane and the pilot are ready.

mikes68charger

My Feedback: (34)

Great it will work out.

But it dose glide pretty well with out power. Just remember to keep your gear up unless you know that you have the airspeed right over the runway

I think I belly landed once with no issues

kiwibandit

Ok, so both engines have been pulled apart and the front bearings removed. Sensor screw holes drilled n tapped. Both engines re-assembled and the whole system changed to spark ignition. The starting and idling is transformed. No more kicking back on the starter now. With my Biela props idle can be set as low as 1500 revs. I prefer to keep it around 1900 to keep it all smooth. Just waiting on my twin sync from TBM now. The engines run very very close in revs right thru the rev range. I could well get away without the sync device, but why risk it. For $100 bucks it's cheap insurance.
I managed to sort out my harmonics issue. A stronger spring behind each throttle barrel solved it. It turns out that the barrels were floating in the slot and causing a slight mixture change. At idle, this was enough to kill the engine.

I'm looking to get in a first flight by the middle of next month. (Feb) I hope to have some more photo's and video before then.

mikes68charger

My Feedback: (34)

I got the twin sync. Nice peace

The only thing bad that has happened with my ASP180 was one had the nut on the exsaust rocker arm come off. And I guess it got hit inside because it blew a hole in my rocker cover. I have also had the exsaust pushrod pop off because the exsaust valve got stuck after a gallon of fuel

But I have read the gas conversion satio have the same issue

I am running 20:1 with shill ultra hp synthetic with regular 89 octane gas

So after ever gallon of fuel I just take the rocker covers off spray some brake cleaner on the exsaust valves then put some oil directly on the value shafts

Why this may sound like a pain but when you consider how fuel efficient these asp180 on gas are its not.

On the stock fuel tanks I can start up the motors let them run for 4 - 5 min on the ground letting them warm up and to make sure all is ok. Bow they are breaking in I just make sure that they are warmed up.

Then I have my timer set for 15min flight time. Land and still have almost 1/2 a tank of fuel. I have even done 2 flights back to back and forget to add more fuel in the stock tanks.

As I only had around 40 flights and a few hours on the ground doing break in. I can tell you on gas they are still breaking in

kiwibandit

I considered changing to petrol but the design of the engine is not really suitable. If the conrod could be changed to a needle roller bearing then I might consider it. I have seen too many engines let go on the bottom end due to the bronze bearing "egging out" and failing. I mix my own nitro fuel at any rate. I generally will get thru a 210 Litre drum during our flying season here in NZ. I have a VERY hungry saito 325 radial which, while it is a joy to behold in the air, has an alarming rate of fuel consumption. A 1 Litre fuel load give about 8 mins of flight time with a reserve of a couple of mins if the runway is busy or you need to go around. A good weekend of flying my warbirds will see me get thru about 15 litres of fuel. My Saito 220 Zues is also good at getting thru the fuel. If you want big power - it equals lots of fuel. I'm involved in speedway so getting fuel is no problem.

Regarding your twin sync device - which brand did you use? I have gone for the "Down n Locked" version. Reading thru the manual - it appears to be very flexible in the setting up. I like the option of being able to use an aux channel to allow engine steering thru the use of the rudder while taxiing. After talking with Ron, I opted to also get the interface unit which will let you plug into the sensor lead of the ignition module. It should make for a very neat installation with good options for setups.

The Kiwi Bandit.

mikes68charger

My Feedback: (34)

I got the same down n lock.

It was not funny but the one time the motor did shut down, it shut them both down like it was supposed to but I was so panicked I forgot to put the throttle all the way down then bring it back up to control the still running motor.

But good news is that I believe this big bird has a good glide ratio

The only real issues I have had has been those 1/4 spark plug caps. They keep coming lose on me and it makes the twin sync try to sync up with a motor with a lose cap. And you have to run one at a time to figure out with one is acting up

If you find a good way to keep the plug wires on please let me know

mikes68charger

My Feedback: (34)

I wish you were closer. I got (a great running) my ass Satio 300 twin last year for Christmas from this site

I couldn't get it to fire on both cylinders so I sent it to Horzon $150 later got it running on both cylinders but he thinks it needs a nee carb because it won't run below 3k. And at $80 for a carb I think I will just spend the $220 to get the full CH ignition upgraded to gas

Just don't want to waste more money into something that might not work. No one around me runs big satio only DLEs

kiwibandit

The rc excel modules I have used have got a 120 degree metal cap which is a twist to lock fitting system. When they are on - THEY ARE ON. I have not seen any movement of the caps so far during the engine runs. Now that they have the higher voltage range it means I can run them off a 2 cell life battery with plenty of capacity.

kiwibandit

Here is a link to my ESM La7 with the radial fitted.

https://www.youtube.com/watch?v=R2RzJJuAlk0

Enjoy. I adore flying this model. To date it has over 100 flights and is still going strong. Long live Saito engines.

Bumsteer

I'm in the process of building what will be my 2nd ESM B-25 and have a question about using Aeropoxy. I saw an earlier reference/recommendation so I decided to give it a try. To the person(s) that used it do have any best practice suggestions? When using the nozzles, clean up, etc?

mikes68charger

My Feedback: (34)

I just use little clear bowls the same small ones they sell at the hobby store or at Walmart next to the plastic cups

I just put what I need mix for a little bit and go. Its great stuff

I like useing the smallest paint brushes from Hobby lobby or any craft store, epoxied brushes will wast alot of epoxy in the brush. You will find out this stuff gose fast so make every part count

Cleans up nice with regular alcohol

Also you can use it like bondo. After it has sat for an hour or so weat your fingers with water and mold

Example. I love to use it to make filets between elevators and fuse on some projects.

tevans55

I'm not much help because I just shoot it straight from the tubes into an epoxy cup and mix it like regular epoxy.

Bumsteer

Thanks for the comments and suggestions. My first use of Aeropoxy was to secure a cowl ring to the cowls. The glue nozzles worked well to place the glue inside the cowl but at the same time they seem to waste a lot of pricey epoxy. In the future I'll use it like regular epoxy and use a syringe for hard reach areas. I'll attach a few photos.

This time I'm using a pair of Saito 180s converted by CH Ignition to gas. I was impressed with the quality of the conversion and the support received from Adrian at CH Ignition.

SWORDSN

My Feedback: (13)

How expensive is the conversion?

Bumsteer

He charged $165 each for parts and a setup fee of $40. I sent both engines together so only had to pay the setup fee once. Return shipping was included. He does bench run each engine after the conversion.

SWORDSN

My Feedback: (13)

That should be a lively B25.I look forward to the first flight.

kiwibandit

Well guys. She flew. And it flew extremely well. As soon as I get the video footage from the lads at the field - I will up load it to my Y-Tube page. I ended up going with my C.O.G. at 100mm back. I'm glad I did as the feel and control in the air was Rock Solid. A few clicks of trim on both aileron and elevator saw it tracking true and hands off. I chose to wait and fit the twin sync module before the first flights. Well worth the effort. Both engines roaring round in perfect harmony was a joy to behold. The engines performed flawlessly from start up to shut down. This bird REALLY knows how to slow up on the landing run-in. Coming in with full flap and about 15% power saw a lovely landing with a fairly short roll-out. Moving the C.O.G. back meant I had good elevator control all the way to the flair. After several more flights during the day and becoming more comfortable with it's flying habits - I feel I will move it forward to between 90 -95mm. This will remove the (floaty) feeling on landing.

All in All I am very happy with the aircraft as a package. I look forwards to getting a lot more time on this bird. Now it's time to take off all the covers and see if anything has come adrift inside. Check screws and mounts post flight exam.

Later.

The Kiwi Bandit.

Eldher

Hey! That is fantastic! Yah, this is one great flying plane as you can now attest
Looking forward to the video. Enjoy those smooth flights!

kiwibandit

Mike! As you also use the D&L twin sync - I was wondering if you could shed some light on a small issue I have come across.
I set my device up on the bench and got it configured the way I wanted it to work. After fitting to the model and ground running - it all appeared to function perfectly and did exactly as it was designed to do.
When I flew it I noticed that over the space of a minute or so, the rpms of the engines started to fall. It was almost as if you were gently and slowly pulling the throttle stick back on the radio. To recover the lost revs, you only had to move the stick and it would immediately go back to whatever the throttle position was on the tx. Not a big problem but one that does cause concern. I got around it by using the throttle the way you would on a sport plane.

If anyone else has come across this - please feel free to add your comments and if you solved it - don't keep it to yourself.

The Kiwi Bandit.

mikes68charger

My Feedback: (34)

Mine don't do that

Could be one motor is running more lean and when you throttled down it got more fuel and got back on step

Eldher

Mike is right, first make sure the 2 engines are tuned right, you'll chase daemons forever if they are not.

While mine does not do this either, here is something else to check. Look at is the setting you have for how quickly the TS responds. There are like 5 different settings to use. Make sure the setting is aligned with the type of engine you have. Normally if this is set wrong the TS will "hunt" for the right setting. However, I could also imagine that hunting resulting in a slow drift of the throttle setting.

Something else, make sure the high throttle stick position setting is set to your full stick position. If I recall (it's been a few years since I messed with this) the light on the TS comes on as you start opening the throttle and should stay on till the stick is in the full throttle position.

Check the mounts and distance of the Hall effect sensors. If the sensors are missing some of the passes of the magnet under the sensor on one engine then it will think that engine is slowing and will then slow the other engine to match.

OH! and don't forget ... make sure you have the "flying in the southern hemisphere" option set to "ON", clearly it defaults to northern.
... JUST KIDDING