Hello All,

I am developing an engine synchronizer for twins, and would like feedback from anyone interested in such a product. This device will utilize state of the art electronics, and will be easy to install and very versatile.

If you have any options that you would like to see on a synchronizer, especially regarding engine failure modes, please respond with them, as they may very well be integrated.
I would like to hear from everyone interested in this product so that I can determine initial production quantities. Please spread the word.

Thank you
Daniel Smith

email comments/responses to

[email protected]

Smitty:

I wont try to give you a flowchart, but here’s what I’m working on.

Inputs to the system are throttle and rudder signals from the rx, and an rpm signal from each engine.

Output is separate signals to the throttle servos.

If it does not get both rpm signals it passes the receiver throttle signal through to the throttle servos with no alteration.

Both rpm signals are sent to counters, the difference is divided by two, added to the pulse time for the slower and subtracted from the faster, with the rx throttle pulse time being the center.

>This eliminates the “Master/Slave” of the EMS system, and therefore prevents the slave engine starting at full throttle, and takes care of any worries about “Stronger” and “Weaker” engines – self correcting.<

>At this point we have the ideal synchronizer for straight flying, but since we want a little fancy, we add the differential command.<

Check rudder pulse time. If greater than 1.30ms and less than 1.70ms, OR if rx throttle pulse time greater than 1.5ms ignore rudder signal.

Check rudder pulse time. If less than 1.30ms or greater than 1.70ms, AND if rx throttle pulse time less than 1.5ms add (throttle time – 1ms)/2 to opposite throttle pulse time.

>This gives differential throttle for taxi realism, and extreme maneuvers in flight, while ignoring normal rudder movement, and still keeping the engines in tune otherwise. Also, if the engines are at 50% power or greater the rudder has no effect. And by basing the added pulse time on the throttle signal we can vary the amount of engine acceleration.<

I can make this work on my P-3 computer, but I haven’t managed to get it inside a small plane. And it’s my ideal sync system.

Hope this helps you.

Twin engines in sync,
. That's best, I think.

Bill,

Daniel
Put me on the list for one. Thanks

Rich and Bill,
Thanks for your input. I really appreciate your feedback. I am about halfway through the programming phase. I will keep you updated on the progress.
Dan

I have experience with the EMS and am very happy with its performance. But if you can come in at the same price with the added features put me down for one.
Sparky

Bill, are you going to market that design of yours?

If so, let us know when and where... I would really be interested in yours...

Mannerless One:
This is a low priority item for me, cobbled up a "Breadboard" prototype, ten (?) chips, 12 volt supply, running time less than five minutes with 1100 mah battery pack. It was also MUCH too heavy to use in anything less than giant scale and the cost also was totally unreasonable.

Partial list of chips:
CPU - 1802
RAM - 2114 x2
CMP - 7485 x2
ROM - 6116
REG - 7805
This is from memory, I did this several years ago and set it aside. Might have some numbers wrong. But I know I was using the RCA 1802 and the 2114 static ram.

That's why I was very pleased to see Dan Smith working on one, If he does it my way, and does it well, I'll buy five or a dozen from him and save myself the development bothers. Provided, of course, the price is reasonable.

The EMS units work, and they work very well, I am using them now. But they don't work the way I would like them to.

And thanks for the interest.

Differential thrust AND sync,
. With Heaven you have a link.

Bill.

I guess this is one of these things... the proper parts... the proper programming... working out a design that draws very little current... not all that easy...


That EMS that was mentioned in earlier posts, where can that be found?

Uncouth:

Memory coming back a bit, my rig used only one 7485 comparator, but it did have two 4020 counters in it.

RPM pulses went into the counters, they fed the comparator, the comparator had three output conditions: A=B, A>B, and A<B. The CPU read the RX throttle and rudder signals, and the comparator output, then sent the servo signals to the engines. All timing was generated in the CPU by software. Making it work was relatively simple, but making it small was not.

Regards the current drain I was trying to convert everything to Cmos, that would remove the need for voltage regulation also. Dan, you're welcome to note this too. The RCA 1802 is Cmos.

Here's the source for the EMS unit.

http://www.emsjomar.com

Last one I got was $90. They work very well. But if you jam the throttle the engines will go out of sync for a moment, it takes about 1/4 to 1/2 second to catch up. Almost too short to notice, but going from full to idle you'll see the plane wiggle a bit. From idle to full the engines usually have more difference in lag times than the sync unit. So long as you work the throttle smoothly you'll never see the delay.

Twins in sync,
. You're in the pink.

Bill.

I dont think current drain will be a problem with the components I am working on. I think I will be able to complete all operations with one small microcontroller. Surface mount technology may be used to keep packaging small, without limiting options. I have yet to decide on which options to include, like the differetial throttle/rudder option Bill proposed. I would like feedback from other people on this to see what the demand for such options is.
Dan

The throttle-rudder coupling may be overkill on a small sport model, though still very useful...

On a large scale airplane however... that would look and sound very smart. It adds a scale note...

I would be interested in one also,Keep me posted when you
get it finished.

Sorry about lack of updates. I have had computer trouble. It is costing me quite a bit of time.
Dan

djsmith, I am interested in your project. I live "next door" down by Mason and have a couple of twins we could test it on :-)
Jon L.

Dan,

i have cought the twin bug and i would like to see what you come up with for a price point on these. I was going to use a EMS system on board but bill has a point that coupling the ruder in for under half throtel to help out on the ground would be a very nice feature.

What are you programing them in. I work as a programer and write in a verity of languages. went to school doing embeded systems programing on motarola hc11 and 56k series DSP's Would love to help this get off the ground.

lee

I have a Safety Sync. I don't think they're made any more. It is a bear to set up but works great when adjusted. You only have to adjust it once. The feature I like best is if you lose an engine it pulls the other back to idle. You pull your throttle stick back to idle and then you can advance the good engine to an RPM you set. If you go past that position the engined goes back to idle. There is also a lead for a strobe light or gear switch. When an engine dies the light comes on or the gear goes down. I haven't tried that mode yet.

Lee,
Thanks for the offer on the help, but I am pretty well set. I am working with a pro who also has been doing this for years. I dont think I am in need of help at the moment, but I will let you know if I do. Much appreciated.

Mr. Bender,
Thanks for the input on that system. I had not considered that strobe light/gear actuation. I will keep that in mind for final features. You seemed to like the pull to idle feature on that system. Have you used a system where it simply maintains the same input, and keeps the engine at the normal throttle setting? If so can you tell me which you liked better, or if both should be included as an option, depending on the application?
Thanks for the input

Dan

Dan:
I had not thought about dropping the gear when an engine quits, that I like.

But just a straight drop to Idle I don't like. That would require setting the idle stops on the carbs, and we wouldn't be able to kill the engines from the transmitter. Also might lead to starting difficulties, if we can't play with the throttles.

Just my thoughts.

If comes the time when I hit the bottle,
. Only then will some one else kill my throttle.

Bill.

The throttle stops on y twin are NOT set. The throttle trim on the transmitter works just like on a single. When an engine quits the othere engine drops to idle as set on the transmitter. I can kill that engine if I want to by bring the idle trim back. I really like this feature as my other (no son board synchro) twin turns into the dead engine and tries to flip over on it's back pretty quickly. luckily I've only had two engine outs so far. One on each bird.
There is a button to to turn off the Safety Synch to start set and adjust.

I have to go with bill on this.

it taking the eng to idel till you respond i realy dont like. The one twin i did have flew fine on one eng. I like the idea of the strob light as a visual indication, as long as it can be made to run were it couse any interferance. When i did have my twin in the air and i lost a eng i could hear the difference in the sound. And all it had on it was a pair of junk OS 40 LA eng stock mufflers and 10x6 props. with a pair of 46 or a pair of 4cy that are louder you can hear the per of two engins go away to a singel engine.

Dan,

i also though of one other thing as far as a routeen that may be a little easer than bills sugestion but better than EMS.

If you choose the week eng on the fly and adjust the strong one to mach. That way if one is slugishe to come up but then over powers the other the soft were can keep picking the strong one and adjusting the week one. with in a % of corse. The reason i say this as I though of bills routeen you would have to program limits for each servo. and make a specal routeen to handel as those limmits were reached. at least at full throtel. Since you were increasing the week and pulling back on the strong. I was thinking what happens your at full throtel on take off or a climing manever. and the week engin is full open and its trying to drive the servo more open (bind). You can get a micanical failer or suffer some realy high curent drains from the system. Just a though.

lee

Lee,
Your system is an interesting idea, but it is still close to a master-slave system, which I would like to avoid. The only difference is that it switches the master and slave around on the fly.
As far as limiting the servo travel, I was going to limit all servo outputs to between 1 and 2 ms. This is the easiest way to do it, and it ensures compatibility with all servos. This solves a lot of problems, and the extra programming necessary is probably simpler by far to the algorithm that is required to switch master and slave. It may require that when the device is installed, the servos may need to be slightly adjusted. I dont think this will be a problem though.
Dan

Dan:

Currently in various stages of preparation are Two Twin-Airs, three Duellists, a second F7F Tigercat, and a PT-E being bashed into a twin.

One of the Twin-Airs is for 0.15 engines, I'll do that one with plain mechanical sync, and the PT-E is electric. But that still leaves five of the seven wanting that "Little something extra."

So. How is it coming?

Bill.

Well, Im making decent progress, but im not there yet, so Im kinda hoping that youll be seeing something by early summer.
I know its kinda vague, but my shcedule is pretty weird, and its the best i can give ya right now.
Dan

Dan
I am really interested in your new sync.Here is the reason why.

With the engine nacelles out 52 " apart and connected by a 5/32 " cross shaft, any little difference any where in the rpm range and you get a vibration in the heads.

Hi Dan,

Sent you an e-mail a bit earlier today. After reading the other posts on the twin sync units already built, it gave me an idea.

One fellow mentioned the Safety Sync system (and I think he is correct that they are no longer being built), and that it had the option of switching on a strobe light in the event of engine failure. I thought this to be a good feature.

Why not go one step further, and have it send a signal to indicate which engine had failed? Using the engine's rpm sensor, the missing pulse could trigger the circuit. The lights could be mounted flush in the bottom of each nacelle or engine cowl so as not to be noticeable (not to detract from scale). And, the presence of either engine's failure signal into the unit could feed a signal to trigger a tail strobe for extra visibility if desired. If the pilot saw the tail strobe flash, he would immediately look to the engines to visually tell which side had failed.

Regards,

Al Parry
[email protected]