Has anyone here used and had trouble with one of these?
What is this wide pulse thing they mention?
Any other comments?
Perry

I did find out that a JR servo rotating clockwise will produce a wider pulse at full throttle.

System is a go!!! It works very well.
Now I must get busy building the C310.
I discovered that I cannot use Futaba servos and a JR radio using this Twin Sync System! Both components must match and the servos must produce a wider pulse at high throttle. All stated in instructions......
I've never has any trouble mixing servos until now. Electronic devices told on me! Lesson learned......

It's very impressive to hear both Saito 120's running the exact rpm. From idle to full bore. Sure, you cannot slam the throttle to the floor, but who does this in a scale plane anyways. You can however progress the throttle stick plenty fast enough.

Twin Sync System from EMS/Jomar, it works! Thanks Mark for all your help!
Perry

ok,, I'll be a dummy here... What is this about?
I remember something I saw a while back that looked like 'disc' mounted behind props and one servo was regulated from rx as a master and other throttle servo was operated from 'disc' as a slave.. it wouldn't allow for instant revs, and if one motor died, it would reduce throttle on the other...
Is this the same type of system?
And how small of a motor/plane can it be used on.. I have a TwinStix with .46LAs which is usually at full bore anyway.. But on my Tiger 60 which has two .46 S/Ts there is more room and it is not used as hard...
And will it work on gas engines as well.. On my 310 I want to use gas <G23+>.....
(questions,, questions...hhmm)
Robby

Hi Robby,

I found the URL, so you and I can both read more about it.

http://rcvehicles.about.com/gi/dynam.../emsjomar.com/

(Click the "Electronic Accessories" link.)
Maybe this wouldn't hurt for our King Air project...

Guys,
The back plates used for the magnets are of course spinner plates. The system comes with magnets. 2 for each engine. I choose to use my own magnets as they are chrome plated.
I tried 4 magnets on each engine and got no better results. So I will be using only the 2 for each engine. The instructions state to crank the Master first and then the Slave engine. You can however start the Slave first. This way is easier. If the Master is running first the Slave servo goes to full throttle and will slowly back down, all the while flooding the engine.
When the Slave is running first the Master will not go to full throttle but the Slave's rpm's will come down the match the electric starter's rpm's, thus much easier to start!
Use the weaker engine for the Master, & stronger engine for the Slave.
I used a small strip of PC board for the sensors and mounted them to a strip of aluminum (brackets) running out from the 2 engine mounting bolts on one side of the engine. I then sloted the aluminum brackets for adjustments.
If you guys need any further assistance I'll be glad to help. Mark @ EMS/Jomar is very helpfull too.

Perry

I've just emailed Mark with a request, to see if that unit could be modified to work a little differently, like a full-size sync system (Raytheon - King Air) I just read about...

Instead of physically setting any particular engine as master, have the little computer monitor BOTH engines, and on a moment-by-moment basis, the one with the higher RPMs is considered the "Master".

In a perfect world, I wouldn't want to knowingly have a "weak" and "strong" engine. I'll be trying to break at least 2 engines in, under as close to exactly the same conditions that I can, and (ideally) get them VERY close, manually. Then, the EMS/Jomar unit would take care of the rest.

Twins give me a little "twitch", when I think about this stuff. Maybe we should start a "Multi-Engine tips" thread here, to collect some new information...

Mike,
I'm sure both of my Saito's are real close to being the same rpm's at full throttle. I ran them without this system hooked up and they did well. One of the engines (Master) has a little richer run up so this is the only reason I dedicated it to being the Master. The Slave engine has a flawless run up. Both of my engines were used with new rings and bearings. I just about have them broken in now. They are the older version with larger fins.
I can't say enough about the EMS/Jomar Twin Sync System. It works and does it well. I can fly my twin with confidence that both engines will be turning up the same rpm's and I won't have to make inflight adjustments on the rudder to keep it straight.
Perry

A "Multi-Engine tips" forum would be a kewl idea.. Aren't there more multi's than there are JETS ..? I know I wonder if some of
the crap I try is worth trying.. And as in this topic, if there are things avail to make it easier or more fun...
Since doing twins I have learned NOT to use cables for throttles
unless it is to be used for full bore running.. Matching engines
is more than just two of the same motors.. Two motors, two mufflers, feeding one tank does NOT work... And yes, can use
a smaller fuel tank per motor on a twin than what would normally be used on a single.. But I want longer flights so bigger tanks
are needed..

I would be interested in what others have in the way of twins, and the more 'off the wall' the better... And of course to see some pics would be great...

RCU ?
Robby

Perry, no offense intended. I need to become an expert on flawless twin operation, in preparation for flying our 1/6th scale King AIr B200 next year. (on my site at http://www.nextcraft.com/b200_construction01.html ) It's so sad to see those big twins go down, even at "Top Gun". So, how to prevent that...

Two things:
First, it seems like we have a pretty good start on a "Twins" thread right here, so let's have at it.

Second, I'd appreciate hearing from any of you who have first-hand experience flying large multi-engine models, so I can learn from your experience. (I'm not new to RC, but am new to twins.) Feel free to email me if you like.

So, I'll start things off with some basics:
From those of you who are successfully flying large multi-engine models, what have you found to be the most reliable setup, as far as tank plumbing, throttle management, on board glow, (or not) yaw damping gyros, etc.? Power hasn't been selected for our project yet, so I'm not looking for engine-specific info, just general setup tips.

Thanks in advance to everyone who contributes!

Guys,

I think we might have better luck with the "twin info needed" post in the "Engines" pages, so I'm going to post the question there.

Care to join me?

No offense taken!

I wish you all the luck in the world for a perfect pair of engines.
There will always be one that will run slighlty different.
Maybe you can go out the back of each engine off of the cranks and connect the 2 together. just for fun!
Perry

A twin forum is a nice idea. I would enjoy taking part and shareing adventures however I prefer medium size airplanes all all of my 'bashes' have been such. It sounds like you fellows only want giant scale. If you want imput about smaller stuff I,d like to 'play'?

JohnBuckner.. I have small twins also.. 55" twinStix.. 70" Tiger
60.. And yes, I have a giant scale Nosen 310 and hopefully getting another one soon.. So, no, it is not all for just giant scale..

jpmorgan .. I couldn't get your BMP to open.. Would be better if you converted it to a JPG .... That way ANYone can open it..

Robby

I've started a "Twin info needed" thread over in "Engines", at http://www.rcuniverse.com/showthread...32&forumid=145

See you there..

Thank you Robbie

First I,d like to say I am no expert in aerodynamics, building or flying but have dabbled with multi's quite a bit with many of them being bashed singles and have accumulated a large number of flights among them.

duelest, K & B .48's

A bashed no name 40 size trainer, K & B .20's in bathtub nacelles

Another bashed no name trainer into a twin boom push pull twin, K&B .40's

Royal P-38, piped OS .61FX's. This one intended for the old SWRA warbird pylon races before the SWRA's demise

Keosho ARF F-82, piped OS .61FX's also for the Swra events

On the table:

Uc-78 Bamboo Bomber with .20/.25's undetermined yet and retracts for controlline. Primarily as a test bed to fully utilize my 'Bill Young' three channel electronic (over the wire) Ukie system.

Last and my favorite a Senior Kadet bashed with four bathtubs for four .15/.20's


The push/pull twin has been a no brainer of course and just flys like a heavy trainer. The only differance between it and a single is the fact that during a single engine takeoff on the rear engine you experiance a right yaw at rotation instead of left due to 'P' factor.

The best one of the bunch has been the conventionally bashed trainer with the twentys. Several hundred flights, nice basic aerobatics and great single engine performance that includes single engine takeoffs with the 'critical' left side shut down. More on why in a bit. This ship has been well received at several full scale airshows.

The two pylon ships, F-82 and the P-38 were failures for their intended purpose. Both were over powered which made the P-38 quite heavy at close to 15 lbs with something just over 700 squares that put the load at over 40 ounces per square. In the 10 or 12 flights it flew delightfully and was fast but during practice on the course I pulled a bit to much 'G' and she double snapped from thirty feet into the ground just like a lightening strike (pun intended), It will live agine eventually but with smaller engines and not as a racer. The F-82 with quite a few more squares to lighten the load also before reaching a race experianced an outer wing joint failure and is total history.

There are two points I would like to share surmised from my dabbling, the first is when selecting power for a twin particularly a bashed twin you will experiance a performance improvement from the fact that when adding an engine even if it is similar total power as a pair to what originally was about the same power as a single. This improvement is a result of reducing the propellor disc loading by close to half and manifests itself in low speed thrust i.e. climb, takeoff and vertical not in speed. Kinda like a large fine pitch prop as opposed to a short course one for speed.

The next point and most important is out thrust on both sides. this one is vital to a multis long life. This is the one factor that makes the little bashed trainer so successful and able to perform single engine takeoffs. It does drastically reduce the rudder work load when you loose one and you will. I just don,t understand why most model designers don,t use it or some odd combination some on one side and not the other. If you research it I think you will find most full scale light twins do use considerable out thrust on both sides.

The Quad Kadet which is going slowly due to my medical condition will have bathtub nacelles that are hinged and wing nutted to adjust outboard up to six degrees and the plan is to use about half the out thrust on the inboards as the outboards.

With the exception of the electronic controls for the controlline twin I have not done anything exotic with tank setups using just individual tanks or electronic yaw control and synchronizers. Not at all aginst it, just like to keep it simple, the rudder gyro is probably a very good idea. A synchroizer may be a good idea on the giant ships, particularly if they may be overpowered ones but on the mid sized airplanes its probably overkill as a slight mismatch does not seem to be a problem and would be even less a problem with a rudder gyro. Here's a thought that distinctive non-synchronus throb is always an attention getter for your audience anyway.

Thank you for allowing me to share and looking forward to your experiances with the electronic apurtenances.


John

You want twin info? go to RCWARBIRDS.com. The forums have quite a bit on twins in the "Twins Forum" including the bashing of singles into twins and gyros on twins. Yes, I flew one of these this weekend.
Twinman
Why should I be the only one to go crazy with multi's