yl5295

My Feedback: (1)

All,

I built an electronic engine sync for one of my twins (Royal Cessna 310). I am thinking about producing it for sell. Do you guys that frequent this forum think there would be a market? It would probably need to sell for about $100.

Here are the key features:
- drives two throttle servos from one channel
- match box functionality for initial setup and when not in sync mode (very low throttle or turned off with AUX channel)
- aux channel input for either enable or disable synch or rudder input for steering with engines
- 4 digit LED for RPM readout of engines
- magnetic pickups and hall effect sensors for each engine
- auto engine reduction to idle if one engine dies (i.e. prevent snap rolls on some planes) The running engine can be throttled back up by pulling stick to idle then advancing again.
- typical accuracy is about +/- 25 rpm upto about 15,000 and about +/- 10 rpm less than 10,000 depending on servo resolution.

Let me know if interested as I will be looking for a few people for doing field testing if I deide to produce this.

It sounds awsome running it the last couple of days on a pair of OS40FSRs thoughout the throttle range being in sync.

Robby

My Feedback: (18)

Jomar Products offers this and can be seen second page, fouth item down..

http://www.emsjomar.com/SearchResult.aspx?CategoryID=6

Item description is listed as below...

Twin Engine Sync System
Works on “Master-Slave� principle - forces Slave to track Master by controlling
Slave throttle servo. Uses small magnets and hall sensors to sense RPM.
Requires a servo on each engine. 1.5 x 1.5 x .75 - weight 1 ounce.
$89.95

Given the reliability of engines today there is less use of this type of
item plus with radios being able to control seperate throttles or the
use of 'matchbox' type of units makes for even less usage of this
type of item...

Now,, having gone thru all that.. I perosnally think it is a great idea..
( but work on the price some)

Robby

Mustang51

My Feedback: (25)

Problem with this is... It is a "Master\Slave" set up. The slave servo responds to the master. Simply put, What happens if it's the slaved motor that has the problem? You better be fast on the sticks.
What 5295s' unit will do is COMPLETELY different.
5295. A lot of guys(including myself) are running twin throttles off of two servos and three channels through mixing so each motor can be opperated independently for run ups or in sync for flight. if you can set this up for such a system, that would be the answer to our problems.
Good work!

Incidently, I am building a P38 on 3W 50s. If you can produce one for gas motors with my twin type radio set up, I would be interested in it, as long as it is NOT a master\slave set up.



-M51

yl5295

My Feedback: (1)

Mine is not a Master/Slave unit. What mine does is has a single throttle input. It then drives both servos to that position (based on the included matchbox setup). Then after a very short delay it slows the faster engine to match the slower one. This will limit peak rpm on the best engine but it would be in sync at all times. It is currently designed with a second input channel for controlling the mode of operation (i.e. rudder or on/off was what I had in mind). I could add a third mode of operation controlled by the AUX channel to allow a three position switch to control whether the throttle stick controls port, starboard, or both engines like you are asking.

Also mine has a 4-digit LED readout (tachometer). If I eliminated that I could reduce the cost a good bit. If I eliminated that I could also add remote glow. Maybe that is the way to go.

yl5295

My Feedback: (1)

PS. Mine should work fine for GAS. I did most of the software and hardware design driving brushless motors through ESCs. I had to change some of the dampening factors for the slower response of glow engines but found that the brushless motors ran better too after changing the timing/dampening for glow. So it should work fine for Gas now as well since I think the throttle response on gas is faster than glow.

yl5295

My Feedback: (1)

In thinking about it the third mode I was just talking about adding is really almost the same as the rudder mode. In rudder controlled mode when the throttle is below the 1/5 point you can control the throttles of each engine with rudder input. i.e. full left rudder if left engine idle right engine full power. Half right rudder is right engine at idle left engine at half throttle. Once the stick is advanced above the 1/5 point this feature is disabled and the engines run in sync based on throttle stick. would this meet your need or would you need the three position switch control?

The other feature I am looking for input on is the engine problem recoverery. I had a P-38 that would snap if an engine failed. I had to immediately cut the power if an engine started sagging or quit. That is really what got me thinking about this and eventually build it.

Obviously, if either engine has a problem the fast engine is throttled back to match it (upto the idle point in case of a dead engine). You can then regain control of the idling engine by pulling the stick back to idle for a second and then you have throttle control again. Does this sound like the right approach?

Robby

My Feedback: (18)

Yes.. That is the way to go...

I would rather see this as a switchable feature so I could use it all the way thru full throttle..

Robby

Terror Dactyl

I would guess that it would be way too hard (read it expensive) to be able to use too separate channels for the throttles, completely not needed since the light just came on[8D], to make sure that the trim will shut off both motors.

I am curious, are we able to set what rpm the default idle will be when one motor shuts down?

yl5295

My Feedback: (1)

I think you realized that there is no need to use two channels since this device drives two servos from one channel and basically give you about a 100 point throttle curve for each servo independant of each other. This lets you setup the servos where the engine are very close without synchronization. Then when you turn on the sync function it drives both servos so the engines are in sync.

The way I have it programmed right now is that the syncro function turns off below 1/5 throttle and passes control back to the transmitter. The initial set up lets you increment or decrement each servo to fine tune all of the settings below (and above) 1/5 throttle. The only thing you have to program is the idle point of each engine in the event of an engine failure. I will probably add a few more programmable things if I take this to market.

Another feature is that it watches for errors in the PPM stream and if three errors in a row happens it performs a PCM lock out type function and reduces both engines to either kill or idle. I have worked with this piece of code a lot and it offers PCM lockout functionality with a much quicker recovery time on a standard FM radio. I personally fly all FM receivers because of the long time PCM lock out typically lasts (except for my turbine which has to have PCM).

Keep ideas and questions coming and let me know the interest level since if I release take this to production the initial cost (to me) is fairly expensive.

v22

My Feedback: (8)

I might be interested in one ,,,looking for the likes to put on my V-22 Osprey twin motor tilt rotor. Let me know if you decide to make them as it sounds a whole lot better than the Jomar one that I have been looking at. I wouldn't need the other stuff so that would help keep the cost down some.
I just noticed it is for ppm and I run all PCM as I need 10 channels
Larry
[email protected]

yl5295

My Feedback: (1)

It works fine on PCM. Just if used with PPM it detects interference and moves the servos to a predefined point just as PCM lock out does. If used with a PCM receiver this feature is not present since the receiver detects interference and continuously sends a valid throttle servo signal. It will drive the servos with a 40Hz PWM signal even if used with a radio with a faster frame rate. It can accept any incoming frame rate as long as the PWM is .5 - 2.5us per pulse (all radios on the market are 1-2us +/- 20% that I know of including high frame rate digital systems).

I will do another prototype build definitely that will result in my having either (3) or (6) more of them. One of my local club members wants to do some testing with it. I want to get a few more people testing them. So let me know if you are interested in being a beta tester. Beta testing should start in a couple of weeks. Production is a couple of months away if I decide to do this. If I do production I would be open to taking pre-production orders at a very low price to help with the initial production costs.

2engsout

My Feedback: (2)

I like the idea of having insurance in the air!! Twinman will agree with me on this one! I have been flying twins for 6 years now and currently have 6 twins RTF. Including a Ziroli P-38 and DC-3. If your unit will throttle back the engine still running within 1.5 seconds, (the quicker the better) after an engine failure, that will help keep the dead engine side from dropping its wing thru loss of lift because of the lack of prop blast over the engine nacell. The Cessna 310 for example, gets 13% of the total lift just from airflow over the nacell. I would switch to .07 speed heli rudder servos to reduce lag time, up or down. I think the remaining engine needs to have a preset throttle program to idle. (3000 RPMS) Here is why. With an engine failure, currently, all we have is seeing a wing drop. We cannot depend on hearing an engine dyeing because you have to figure there are ALWAYS going to be flyers that would rather fly there trainer than watch you fly your twin!!, so you aint gonna hear nothin! When the engine goes to idle, we will know instantly that the probability of an engine failure is HIGH, and we will excecute procedures accordingly! Meaning, push the nose down, bringing the throttle stick to idle, correcting with rudder, getting the wings level, and then bringing the power back up if necessary, to 1/4 throttle to stretch the glide. Very few RC aircraft will maintain altitude with only one engine running. We don't need any LED readouts. I have always used the heli program in my TX the fly all of my twins. The throttle ch for the left engine, and the pitch channel for the right engine. With hi resolution BB servos and NO SLOP or binding in the geometry, I tach the left eng at 1/4 throttle and then go to the pitch ch and adjust the % at 1/4 throttle stik position on the right engine and match the RPMS. Repeat for 1/2,3/4. I only have about 25% throttle at 1/2 stick so I can transition more softly at low power settings for adjusting my landing speed with more precision. The above procedures have worked well for me, but dose nothing for me when an engine dies. Thats where YOU yl5259 comes in!! I want insurance!!!! So do all the other twin flyers! You can send one to me and one to twinman for beta testing anytime. I had the Jomar unit and the lag time to sync was too slow for my taste and dose nothing to the remaining engine that is still running at full throttle. What do you other twin flyers think?

Mustang51

My Feedback: (25)

The whole idea of a unit like this is to match the rpm of the good engine to that of the bad. In the case of an engine failure, the good would match the rpms' of the failing motors rpms' down to say idle then keep it there until the throttle stick was moved to the idle position then slowly advanced for power. The reason twins run into problems is caused by the sudden induced yaw caused by a strong running motor and the quickly failing motor and dead drag inducing prop.
In your scenario 2engsout, you have the good motor responding to throttle down AFTER the bad motor fails, "THEN" quickly (or ..."the quicker the better" as you put it) throttling back the good motor. By doing this quickly, you only induce more side to side oscillation, then a snap.
I say, If you match rpm down through the power spectrum, you'll have a better chance at survival.
You are right though. We don't need led's. We need good comon sense automatic throttle management that will give us back control as soon as we ask for it.
This is a great idea 5295, keep me in mind for beta.

-M51

v22

My Feedback: (8)

yl5295
That would work out about right for me as it will be late this fall or early next spring when I get the new V-22 back up as I am redesigning the nacelle mounts and the whole gear box units that failed the last time. Send me one too.I'll PM you my address.
Thanks
Larry

yl5295

My Feedback: (1)

Great you guys got the concept. That was exactly what I am trying to accomplish and I feel like this device should do. Match good engine to the bad (or slow). And when an engine fails idle the other one. The trick is to let each engine spool up and stabilize before picking the slow engine but quick enough so you can not hear a sync difference. You can not always slow the faster engine or both engines will work their way back to idle. Then implementing this algorithm with throttle changes taking place. That is the tough part of the software that I think I have worked through. The idle one engine when the other dies is easy. The goal I was striving for was the unique sound of the engines being in sync through out the entire flight and throttle range and no yawing on take off (with out adding a nose wheel gyro).

I lost a P-38 that this would have saved. Now the only flying twin I have is a rather ugly ME410 with the engines very close to the center line with an oversized vertical stab. It is very well behaved but still can get upside down with a flame out at full power. That is why I wanted this before I start flying my Cessna 310.

Sounds like I should remove the RPM readout. The rpm readout was really for the heli rotor speed governor version of the product. The good news is that frees up some pins on the MCU to add remote glow and plug sense for each engine and some more switches and buttons to ease the programming interface. I was trying to use the same PCB as a helicopter rotor speed governor I am building and will definitly take to production. The led readout is needed on the heli so you can program the head speed you want on the bench and know what you will get rather than having to have two people and an expensive view through optical tach and testing by flying it. The bad news (for me) is that now that means a different PCB I have to have built. I am also working on a 2x4 matchbox. Maybe I can design it to use that PCB.

I don't expect to sell many of these but I can put a few in each production run of heli governors I build.

In terms of the response time of the device. It is much faster than the response time of the engines. That means it can move a standard .20 sec/60 deg servo much faster than the engine rpm responds. For example it could update a servo 20 times before the engine RPM would change 30 rpm (speaking for an OS 40 FSR). It could update a servo about 5-10 times on a brushless esc running a 2025-4200 brushless motor. A high speed heli tail rotor servo is not going to buy you much (I actually did my initial testing with a Futaba S9253 which is the one you are talking about -- 0.08sec/digital). It let me see how the device was responding visually but added no benefit as the engines responded much slower than the servos could move.

jaka

Hi!
Sorry ! But its more fun, setting and controlling the engines by your own knowledge.

Regards!
Jan K
Sweden

30 years in this wonderful hobby/sport

Robby

My Feedback: (18)

Jan,
Where I myself, do agree, this product would be a good way to
get people to try out multi engine planes that have lacked the
confidence to do so... So if this product saves a plane or makes
it so more will fly multi planes,, then thats a good thing..


Remember,, You won't find Nirvanna if you don't have any nerve ,,
this is a way to help aquire that needed nerve..

Robby

lrb75

My Feedback: (12)

I think it would be a great product. Some people will like it so they can taxi back in with a twin float plane. If you could keep the rudder function on at high speed you could do some interesting spins. One of the fliers at my club used a product called an engine sync 2000, I think. He said it was much superior to the EMS/Jomar product and the way he described it work as yours is intended. Apparently it has been out of production for several years. Keep the price under $100 and make it reliable easy to use and set up and you should sell quite a few with all the KMP and VQ P-38, B-25s that are going around. I have two p-38 kits and a p-61 to build.

2engsout

My Feedback: (2)

If you can get this thing working with 100% reliability, as advertised, with no glitches, I'll take atleast 3 of them! There are some beutiful twins here in the Omaha area that will NEVER fly because the owners are terified of losing an engine and crashing! But I believe they could handle a unexpected symetrical power reduction without much of a problem. If they new in advance that a power reduction was the worst case senerio, they could watch for it, and would maiden their hanger queens and be able to enjoy all of their efforts!! I was the event co-ordinator for the 2004 "TWINS ACROSS THE RIVER" multi-engine only fun fly in Council Bluffs Iowa, and now I see that there will be another multi engine fun fly in GA. this summer!! Congratulations guys!!!! You will enjoy it!!

roltech

Right on! I would get one when there are available.

roltech

2engsout

My Feedback: (2)

Mustang 51 has a good point about the good engine following the failed engine rpm down towards idle. If there was, ,say a 400 -500 rpm dropoff differential, that would have to occur before the good engine executed its rpm decline, then seeing the plane slow down will be your first que that something is not right. Don't depend only on your ears, because there will probably be other planes flying. If, on the other hand, one of your 2 stroke engines was set a little rich, as soon as you get to altitude and back of the throttle, it could develope an intermitant 4 stroke and drop the rpms off 300-400. That is NOT a good reason for a power reduction on the good engine. You will probably recognise this condition, land and adjust your needles. Thus, the 400-500 rpm allowed rpm diferential.??? What do you guys think?

yl5295

My Feedback: (1)

The it works is the engines will be in sync (i.e. +/- 25 rpm difference). The engines will follow each other down to the idle point. So the scenario you discribe will not happen. If you throttle up and one engine is rich then lean engine will be set to the rich engine's rpm. If you throttle back and one begins to four stroke the lean engine will be throttled back to match it. The only time the good engine is throttled back to the programmed idle point is when RPM of the other engine drops below 2000rpm. So an RPM differential does not need to be set since they will always be in sync.

The way the algorithm makes this work is when the stick is moved it moves both servos to that point then syncs the engines.

Mustang51

My Feedback: (25)

Why wait until there is a 400-500 rpm diff? Granted, in twins, that's not that big a deal, but here you have a system that is going to keep both motors running verry close to each other. The more closely twin motors are matched, the less likelyhood of a "typical" twin demise wil happen.
5295, The only suggestion I have(because I think you have this thing nailed), would be to allow 2rx input for those of us running 2 rxs'. I don't know exactly how you would do it or if it's even possible but this would allow your "sync" to follow the path of " best signal" . If one rx fails(for whatever reason), your "sync" would "listen" to the strongest signal and you would still have control of both motors as apposed to loosing a rx and now only having control of one motor.
What do you think?

-M51

yl5295

My Feedback: (1)

I could add that if needed. I dont think that many people run two RXs though. However, let me ask another question. Since I am eliminating the LED display and adding onboard/remote glow drivers to it, how should the glow drivers be controlled? If I need to add a third channel input to control remote glow then I could also make that third channel input a backup receiver input if programmed to do so (i.e. one or the other but not both). I was thinking that the glow plugs could be turned on after power up if both RX and TX turned on and throttle below 1/5th point for 60 seconds. I would have a RED LED to indicate glow plugs turned on. If this is OK then I do not need a third channel input. If everyone wants a third channel input to control the glow plugs then I can add a programming option for your back up receiver.

yl5295

My Feedback: (1)

To make sure my response was clear to 2engsout. It does not wait for an rpm difference. The engines are sync'ed. If one goes below a set RPM then it idles the other one.

How slow does a big gasser idle? I have never tached one? I will do that at the field today if I can remember on my 50cc gas aerobat. I can program the the rpm it decides an engine has failed and right now I assume a failed engine at <2 rev/sec (120 RPM). Maybe I should raise that if a prop is free wheeling due to airspeed?