Mustang51

My Feedback: (25)

I personally think you should forget about the glow drivers and just concentrate on the sync.
Glow drivers are already available and if you choose, you could make them a seperate unit that is hooked up to the throttle servo. Or, you could just make it work with a "Y" harness comming off the throttle servo port of the rx.
Gas guys do not need glow driver capability. Make that unit seperate, or make a sync with out glow drivers. Most gas guys would rather have 2rx capability.
A typical idle on a gas motor can be around 800 rpms'. There is a lot of variance depending on motor and prop combination.
Dead motors do not free wheel do to airsped. The only time a prop will free wheel is if the prop nut came loose or the crank shaft is broken. In either case, the motor is useless.

-M51

twinman

My Feedback: (2)

Reference the idea of rudder to engine slave at low throttle setting...NO<<<NO WAY>>DON"T DO IT!! Been there done that...NO!!!!!!!!!!! Danger Will Robison...noooo!!
In one of the after market programming fooks for the Futaba 8 channel...an otherwise very good and useful book, it tells how to do this exact mix. I tried it.
If you are taxiing slowly to the field and turn the rudder or wheel, one engine speeds up rapidly and dangerously. The plane accelerates and jerks sideways. Now you panic to get it back straight and the process reverses...now the plane is accelerating in an ever widening zig zag. I cannot run that fast often!!!
While I now do use rudder to throttle mixing, I ONLY allow it to function beyound 50% throttle.
My two cents.
Twinman

Mustang51

My Feedback: (25)

*K*I*S*S*

yl5295

My Feedback: (1)

I (think) I'VE GOT IT!!!!

- basic sync with idle down on dead engine!!!
- programmable idle point for the dead engine
- I think I will have a second channel input for independant rev up only (3 pos switch for linking throttle to left, right, and both engines)
- I will remove onboard glow (for the product going to market) but the design will support it as a manufacturing option (and I want it on my planes)
- No rudder input steering with throttles...

I estimate about two weeks for the protos...

Thanks,

Mustang51

My Feedback: (25)

[sm=sunsmiley.gif]
[sm=thumbup.gif]

[sm=sunsmiley.gif][sm=thumbup.gif]

2engsout

My Feedback: (2)

OK, I understand and I like it so far! Lets say your flying along at full throttle like I do, and one engine begins to overheat and the rpms sag thier way down to 2000 RPMS before it stops turning. That could take 3-5 seconds. I've seen it happen. By the time that sagging engine drops below 4000 RPMS, that spinning propeller disc is producing 5 times as much drag as a completly dead engine. Thus, you are well into TROUBLE !!. Remember, at 65 mph at full throttle on 2 engines, at 7000 RPMS, everything is fine. One begins to sag. The plane immediatly begins to slow down = FACT. When the sagging engine is down to 6000 RPMS, the plane is just beginning to yaw=FACT. By the time its at 5000 RPMS it IS yawing and slowing even more=FACT. If I can't here my engines comming out of sync, at what point dose this rapidly growing crash inducing yaw tell me to throttle back the good engine??? I like Mustang51 idea that the good engine should follow the bad engine down= NO YAWING to scrub off all my airspeed!! BUT, lets just say, for discussion purposes, that when the failed engine drops down from 7000RPMS to 6000 RPMS, the good engine begins its RPM reduction program and follows the bad engine in sync all the way down to 3ooo RPMS. At that point, the pilot would have to bottom his throttle stick, and then he could regain control of the good engine, with a preset maximum rpm of say, 5000 RPMS? Even at full stick he is only going to get 5000 RPMS out of the good engine. That 5000 RPM max will keep the plane from snapping when the pilot begins his recovery. Even if he is in a panic, he has only got enough available thrust to stretch the glide. And that is ALL he should be trying to achive, since very few twins will even maintain altitude on one engine. I have seen where a pilot was attempting to maintain altitude to make it back to the runway at full throttle with only one engine. He was pretty low when his engine quit and since there was NO rate of decent, the plane continued to slow down until its airspeed would not support the indended control surface input. Thus stalling all surfaces and snapping into mother Earth! Had the remaining eng been limited to 5000 RPMS, a very nice CONTROLLED rate of decent would have occured!! Yes, it would have been short of the runway, but still in ONE PIECE!! This type of setup sounds good to me and the preset RPM max would be adjustable to suite the individuale planes requirments by the pilot.

Robby

My Feedback: (18)

I would say go with the O/B Glow system,, as an option...
Make unit able to accept it and make the O/B glow a seperate
available option to those who want it...
So then you would have say, an 80$ unit with a 30$ option...
Everyone wins,, including you..
Where I would not use it on all of them, there are a couple it would be handy to have...

Mustang51

My Feedback: (25)

2engsout... DUDE!!! Why can you not understand this? The whole idea of this "sync" unit is to avoid the adverse yaw created by a sagging engine by matching the rpms' of the good motor to it. THE MOTORS NEVER GO OUT OF SYNC MORE THEN A FEW NOMINAL RPMS'. Forget about the differences of thousands of rpms'. It doesn't happen with this.
Why would you (or anyone) want to put restrictions on the throttle? This is a time when you might possibly need all the power you can muster from the good motor, why limit it?

Your friend lost the plane because he was low when he lost an engine. In that situation, limiting the good motor to 5000rpms' instead of 7000 only makes the walk to the crash site a longer one.

It might not be a bad idea to ... If a motor starts to drop by more then say 500 rpms' to have the unit switch on a mars beacon, or any other signaling device to alert the pilot that somethings up so he can set up to land right away. Take the guess work out of it and the worry about hearing twins in a full pattern\sky.

-M51

JL1

My Feedback: (93)

I have Duelist, a Whirlwind and an F-82 ready to test your device. Where do I sign up?

yl5295

My Feedback: (1)

Let me finish it and put some testing on it. I'll offer pre-production or initial production units really cheap on this thread/forum when it is ready with a full refund if anyone doesn't like it and a year of free sw upgrades in exchange for the help and testing... should be just a couple or three weeks or so. Thanks for the feed back.

Terror Dactyl

If there is a list that you want to put people on I have two 60size twins, one which is a 96" WS.

I would be glad to test a unit

yl5295

My Feedback: (1)

I think I just realized what 2ENGSOUT was talking about and he has a valid point!!! The sync device moves the servos to the throttle position. Then it detects the low engine and syncs the faster engine to the slower one. So what if the faster one under sync control dies now?? Let's say that Engine1 is the left and Engine2 is the right. You advance the throttle to 3/4 stick. Servos move there and engines speed up. After a very short delay (throttle response time) the slower engine is determined. Let's say engine1 at 6500 rpm and engine2 is at 6700 rpm. Engine2 is then throttle managed to track engine1. If engine1 dies engine2 will follow it down in RPM to idle. However if engine2 starts sagging its throttle will be opened to full throttle to try to sync to engine1. At some point now the device has to switch to throttle managing engine1 rather than 2. I think this may have been the scenario that 2ENGSOUT was talking about. You could trigger to switch which engine is being managed based on an RPM difference as one option that I think he was suggesting. I think a quicker solution would be to check for full throttle on an engine that the rpm is still lower than the other engine and trigger the switch of the engine being managed. This will cause and almost immediate change that still should cause the engines to throttle down together regardless of which engine dies. I will test this on the test stand today. Thanks 2ENGSOUT... I think I get it now!!!

flydoc

There used to be just such a system on the market in the early '90s. It was called the "Safety Sync 2000". I have one of these units installed on my Ziroli B-25, which has had hundreds of flights over its 14 year life so far. The unit has saved the B-25 on multiple occaisions. A unit such as you describe would be an excellent product to have available again. I'd be a ready customer for it.

William Robison

My Feedback: (3)

All:

I am very interested in an engine synchronizing system. I am totally “Twinsane,� and have several twins.

I’ve been lurking on this thread, decided it was time to make a post.

I have used the EMS/Jomar system, and while it works there are things about it I do not like.

My main dislike is the “Master/Slave� arrangement – one engine is controlled directly by the tx signal, the other gets a signal to make the rpm match. For this reason Jomar says to have the weaker engine as the master.

My ideal system – simple to implement, and still not expensive:

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

Output is signal 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. In other words, if one engine dies the other reverts to normal control

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 pulse time being the center.

>This prevents the “Master/Slave� of the EMS system, and therefore removes the slave engine starting at full throttle, and eliminates 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. And by basing the added pulse time on the throttle signal we can vary the amount of engine acceleration. Another advantage is that the rudder signal is ignored in normal flight, otherwise adjusting the rudder trim alone could cause an out of sync condition.<


Just my thoughts.

Bill.

yl5295

My Feedback: (1)

I completely follow you and the design I am working on should be low cost and do what you are asking for. I like the approach of RX being the center. The only down side I see initially with this approach is that it works for mid-range but a different algo will have to be used for full throttle. A simple mod though.

There are two other down sides to this. When you divide by 2 you loose 1 bit of resolution (unless you do floating point calculations which is expensive). I am finding that extra one bit is important when the resolution of the radio system is less than what required to get a perfect sync. The second thing is if you increment the low engine servo and decrement the high engine servo you have now made a step of 2 (again loosing one bit of resolution or making 2 the minimum servo change rather than 1). It is basically the same algorithm I am doing but a little less precise. You can argue that if you have enough bits of resolution then it is not an issue. However, what I have found on the bench is that the RX and TX are the limiting factor increasing the number of bits of resolution do and increasing the "counter or increment clock" do not improve servo accuracy.

If you think about it 3K-15K rpm is a wide range to try to get servo with limited resolution to drive to an exact match. I find that the resolution of my Futaba 9C (or any radio) is only about +/-0.01us. I tried it in 1024 PCM mode also with a 9ch pcm receiver and found the same thing.

The other problem I have found is that without dampening in the system the servo oscilates arround target RPM. So this has to be worked out based on throttle response time and servo speed. What you will find with your basic algorithm is that the servo for the slow engine will increase too much and the reverse will happen on the other when the engines catch up to the servo they will be out of sync in the other direction and then the reverse will happen and oscilations arround target sync rpm will happen.

Thanks for the suggestions and I will put these modes in it for you.

William Robison

My Feedback: (3)

yl5295:

You have a good point about losing resolution in the software, but as you also said, the servos aren’t that good anyway.

Damping is easily done with a delay loop subroutine called between iterations of the main loop:

For n=0to999\next\return. Recoded for whatever you’re using. C? C++? Straight assembly?

The terminal count would need to be set for aprox 1/8 to 1/10 second. The Jomar uses about 1 second, it gets annoying to wait for it to catch up.

I really think the only place I’m adding anything is ignoring the rudder signal for about 1/3 of its travel around center – otherwise any rudder trim would throw the engines out of sync.

Bill.

yl5295

My Feedback: (1)

You are right about the delay loop but the amount of delay changes depending on how far out of sync you are. Yes the only change is ignoring rudder input arround center.

Coding is macro assembly.

yl5295

My Feedback: (1)

Bill,

I am currious as to how you came up with 1/10 - 1/8 sec for the delay loop. I am fine tuning the dampening now and I find that those are way to fast near sync? I can hold brushless motors now within 30-40 rpm difference with my dampening parameters with four poles (i.e. forth order dampening equation). I can still hear a slight oscillation in the brushless esc. Gas/glow engines are going to have a much slow throttle response and need an even slower response time.

William Robison

My Feedback: (3)

yl:

I picked that time out of the air, based on the delay in the Jomar unit. The Jomar, I think, actually has a 1/2 second delay, and it gets irritating waiting for it to catch up. If you have to keep a long delay I suppose you must, but the shorter the better.

If you sell a user programmable version the delay could be included, that way faster responding engines could be accommodated as well as slower ones.

Bill.

yl5295

My Feedback: (1)

Not a bad idea for programmable servo gain. As I mentioned the delay changes based on rpm difference. For a brushless (4200KV on 12.5V lipo) it seems that .25sec is a good value if rpm difference is <50 rpm. It is much faster response time if RPM difference is greater. I.e. No delay at a 200-400 rpm difference

rslstft

My Feedback: (10)

Well, guys, I am going to have to go back and re-read all these posts and see if I can get it all to sink in. I currently have 1 twin, but it isn't much of a problem with one engine out as it isn't very big. I am starting a VQ P-61, so I too would be VERY interested in this unit, but I too would like the option of a glow driver. After all, the cost of 2 engines, airframe, landing gear, and a boat load of servos larger twins take, a $100 dollars or so as some insurance of getting my plane back in case of problems would be cheap in the long run. Sign me up for production unit!!

Russ

eagledancer

i am interested in one for a future twin

yl5295

My Feedback: (1)

Guys,

I was traveling last week with work and it was raining today so I couldn't go flying so I worked on this. I got past what I think are the last control issues in throttle management. It works great!. I have the final prototype PCBs ready to send out to manufacturing. So I am going to build 6 final prototypes with no RPM display and optional remote glow like I envission the final production units. I am going to keep 2 of the six and send 2 more of the six out to multi-engine contest directors that have emailed me. I will post the instruction manual shortly and am looking for the two final beta testers. After that I will take preproduction orders for either 25 or 50 units. The MSRP will be well below $100 since I removed the RPM readout. Preproduction I will sell them at half price which will be somewhere between $35-45 + shipping with a no questions refund policy for 30 or 60 days. More details to follow. I will try to post the instructions and a video of it in operations within a couple of weeks.

William Robison

My Feedback: (3)

yl:

Put me down for two.

Bill.

yl5295

My Feedback: (1)

OH... one other problem I solved is now the engines are completely controlled based on the target stick position. No - good or bad engine - no engine following another. Thanks to Bill Robinson there is now no delay (less than 1/20th sec response time on all fuctions) and both engines track each other with minimal to no oscillations. This is going to be a great product I think. Slow engine increases and fast engine decreases to an average of the stick position. If either one dies the other follows it down to idle with no delay (actually the sagging engine throttles up while the good engine throttles down and tracks it down to idle).

I can't wait to get my twin in the air now with one of these after burning 1/2 gallon of fuel on the test bench with a pair of engines testing this thing out. I intentionally setup the linkage so my engines were +3K rpm out of sync and this devices buts them in sync within about ~10-20 rpm in a fraction of a second. Hard to say which sounds better - these twins or my turbine???