Governor for a Wren

[lperagallo]

I'd like to put a governor on my Wren MW54 two stage. Is there anybody out there who done this sucessfully? If so please post how you did it.

I fly Bergen, so my thought is to use the fan on the second stage as the point to pick up RPM. This mimics the flywheel of an engine. I am using an optical pickup because I can't install a magnet and get a clear shot with the pickup. I will use an optical sensor with a MultiGov. I can mount the reflector tape on top on the fan ring and the pickup vertically aiming down so there will be very little if any noise from outside light sources.

I was then planning on using the governor just as I would with a Gasser or Nitro to control headspeed except I'd plug the FADEC throttle channel to the governor. I may have to play with "accelerate and decelerate" parameters in the FADEC, but I'm hoping settings within the MultiGov can help me smooth things out.

Please feel free to share your opinions on my plan. Again, if there is a post somewhere here that I couldn't find, let me know.
Lou

[Coolice]

Hey,

It will be interesting to hear how the MultiGov copes on a Turbine, as due to the Turbines nature finding a govenor which works well with it can be a problem.

In the UK, some have had good success with the Model Avionics Throttle Jockey PRO as a basic head speed govenor/limiter. Myself I am awaiting a dedicated unit which is being worked on that will combine an ECU & Govenor together which is the ideal situation.

On the other hand and this has been discussed many times before (and argued about) the reality is with a well setup pitch & throttle curve a govenor isn't needed. However for ease of setting up you cannot beat a govenor, hence why electrics are so easy to get flying.
.

[Intrepid175]

It's been a while for this conversation. Had any luck?

Just curious!

[bcook01]

lperagallo

I have researched this in depth over the past few months. Here are my conclusions. ( I do have some expertise in this field).

1) Any gov must have some fuzzy logic to determine flying characteristics and adapt accordingly. ie 3d vrs AP work.

2) Turbine speed must remain up near top so throttle response is faster. End result is more engine wear and fuel consumption. That means > 140k rpm all the time. note: More energy stored in the blades and less needed from engine

3) To run limits it needs to see EGT (working near limt.... Hot and high with heavy load)

4) the processor needs to be able to see both rpms (engine and second stage).

5) There is not the rpm control with the second stage, especially when quickly unloading the blades. You almost need an electric break to dissipate energy. hmmmm. (this is old golf cart technology) Wouldn't that be a ........"jewel".:YeaBaby:

Summary

It depends on application which will be the limiting factor for acceptable control. For AP you hardly need it but it would work well. For 3D you might get it to work but not with the control you would want or expect from Direct coupled systems.

Tight control = 1 stage. Economy and ap apps = 2 stage. I can see these are the tradeoffs.

I am sure this is why Wren is struggling with the FADEC / Governor as it will require more inputs and additional programming to incorporate system. This is $$$ that needs to be put into development which I see to be somewhat costly but more...... time consuming. A real time data downlink needs to be established to get the results for programming. The end result may (probably) not satisfy the market. This is strictly a business decision based on market potential. :arggg:

For now and the near future you have two decisions (actually three). 1) competition, 2) p&t curve with 2-3 idle-up curves, 3) go back to nitro or gasser.

The turbine optimum applications are electric generators and aircraft flying for 15 hrs at 40k ft. ... "stationary engines"

Maybe this is why there are no automatic transmissions and turbine engines in the NASCAR circuits. :lol:

BTW... no one has come up with some #s or % rpm control 1200 +/- 10% - 5% ? Has anyone thrown on an eagletree logger with some real numbers? What is acceptable ? and what is the application? Now you can see where Wren is coming from.:confused:

I would be interested in persuing this, however, multi p&t curves work for the type of flying that I am doing knowing the limitations imposed by the technology......... or such time we see trickle down from the military apps:shock:.

is engine life and fuel consumption worth it for the gain ?

Just MY conclusion.

Bob

[lperagallo]

Bob,

You've done a good job summarizing the challenges. I, too, have found that the combination of Pitch and Throttle curves are the best option as they are working well for me now. I'd like to preserve my engine and run in modest output ranges so I'll stick with a max RPM of 130,000.

The creator of the Wren Fadec has raised some interesting comments and although it isn't impossible to do, it will take him some time to create an integrated unit.

Lou

[Sara]

Bob,

That is one of the most thoughtful and sensible posts I've ever seen on this subject! You are absolutely right that we have to look at what we gain from a governor versus the time and money used to produce it.

For the moment, all our efforts are going into the 44 heli engine, which is likely to prove much more popular than the introduction of a governor. On the ECU front, the kero start is also in the queue (line, to you guys in the US) before the governor.

I'm going to keep your post handy to send to people who ask about governors, if you don't mind.

Sara Parish
Wren Turbines

[bcook01]

Sara

you are most welcome to use the information.

The 44 seems to have real potential, and we cannot fault you for persuing this avenue.

wish you the best in your endevours. :cheers

Bob

[Peter Wales]

Theis may be very logical and inciteful, but has little basis in facts. The true fact is, Wren's engineers dont know how to make a governor work on the engine. On the other hand Jetcats engineers do and so it comes with a governor.


My last flight with a turbine Cuatro showed a maximum turbine rpm of 117,000 and an average of 97,000. Nowhere near the maximum sttting of 165,000. The idea that fitting a governor and getting it to work requires the turbine to be running near maximum is a fallacy. The Cuatro headspeed would never vary by more than 50 rpm even when doing a roll and going through zero to negative pitch.

Sorry Sara, you make make a fine product, and I would love to use it, but not until you get a governor working.

[lperagallo]

Peter,

I don't remember anyone asking for your opinion. We all know you are a JetCat bigot and no friend to Wren. I have found that throttle curves are easily set up for a Wren and a governor is not really needed. Since I haven't seen any 3D video flying of you, I'll have to assume your style of flying is less demanding then mine.

Lou

[fr8brkr]

I'm not taking sides here but, your original post did request the opinions of "others" without specifying whom you would not like to reply. I'm hoping to join the Turbine community this year with the MW44 and Bergen as its platform. I just hope that when I have questions or ask opinions of others it doesn't stir up the kind of non productive comments seemingly being passed on here.

[Peter Wales]

Lou, thanks for your unpleasant reply, very nice of you I am sure. As it happens, I had one of the first Wren Cuatros ever made, have had a Wren Predator since then and curently own several Jetcat variants and 4 Jakadofsky's. I would really like a Wren turbo prop unit to go on my Coaxial heli, but I am not going to fit one until the speed can be governed.

Your style of flying may be a lot less graceful than mine, but on a full power climbout, you need every rpm you can get on the turbine and, as I said, mine was nowhere near the limit.

As for your comment that "throttle curves are easily set up on a Wren and a Governor is not needed" , if thats really the case, why did you ask for one in the first place?

Obviously, thats a lie, and you do want one, as do a lot of other people.

[bcook01]

For now and the near future you have two decisions (actually three). 1) competition, 2) p&t curve with 2-3 idle-up curves, 3) go back to nitro or gasser.

Peter

I was discussing governors with relationship to two stage vrs single stage turbine design. It had nothing to do with Wren. Governors were first designed by Fulton (Englishman) and is not considered rocket science. You automobile cruise control is a good example.

It all boils down to the type of flying, design of engine, and the end results that are needed.

I know that with the use of a simple comparator circuit, a hall effect sensor, and 20 lines of code I could have a governor...... not to say it will satisfy the needs of the market, nor will a cruise control work in all circumstances. Turn your cruise control on while driving in icy conditions and let's see where it takes you.........

I am sure any simple governor can appear to maintain control in normal flight conditions......:thinking:thinking

I thought the forum was to share knowlege and experience?

Bob

[Peter Wales]

Bob, the forum IS to share knowledge and experience. In that, you are absolutely correct. Lou's initial question was how to put a governor on a Wren. You came up with so many facts showing it couldn't be done on a 2 stage turbine, and yet the SPH5's I use in my Cuatros all have multispeed governors which lock the headspeed in pretty accurately.

I have had someone tach my heli while I do the wildest maneuvers I can, and the headspeed stays pretty constant, within 50rpm or so. Granted, my style of flying is not violent, but changes of pitch and hence load go from lots of positive to lots of negative and the rpms dont change.

Equally, as I said in my previous post, the turbine is nowhere near its maximum rpm limit so most of your arguments and conclusions have been shown to be false in my experience.

As you stated, I am sharing my knowledge and experience and it seems that it disagrees with yours. Have you actually owned and flown a SPH5 turbine? Is the knowledge and experience you are sharing from actual experience or hearsay and guess work?

Let me say once again, I think the Wren is a fine piece of engineering and I think Sara will agree with me when I say I have been pestering them for about 5 years to add a governor. As soon as they do, I'll be buying them, but I'm not holding my breath.

[cbergen]

Notwithstanding Lou's reply,

Initially, he, like a lot of people, were looking for the "EASY" way out with a governor. I don't remember at the moment exactly what was occuring but his particular engine/fuel pump/ecu, etc, something was causing a fluctuating RPM between flights.

His curiosity for a governor stemmed from that, NOT the "difficulty" of setting up pitch and throttle curves.

The offending item has since been replaced, and the engine has settled down to operate properly on pitch and throttle curves and no governor, which Lou now understands is not at all needed.

I think you would agree that if there is some other malfunctioning piece of equipment such as a fuel pump, even a governor would have a difficult time doing it's job....

I have the Jetcat SPH5 2 stage sitting here with me now, the plan is to have it in an airframe and flying for IRCHA, to do a side by side direct comparison. 2 identical helicopters, one with a governor, one without.

Any advice you care to offer on setup and installation?

[Peter Wales]

Hi Chris,

I am glad you are putting your money where your mouth is. I will be very interested to hear of your opinion on the final machine.

I have no advice to offer on setup, it's easy and I doubt if there is anything I could teach you about turbine helis in general. However, if you have a question, I would be happy to help.

I have elected to follow your example and put my money where my mouth is. I have just ordered a Wren and Cuatro kit, but I'm going to try and get a governor to work on it. It will be an interesting project, and as Sara says, it will provide her with a bit more leverage to get her guys to get a governor working if I can do it.

If I succeed and dont crash it before, it will be interesting to see who can maintain the better headspeed control at IRCHA, your Wren without a governor and my Wren with one.

[cbergen]

It's a date!!

We can also discuss some large electric details as well.......

[bcook01]

Peter

I never said it couldn't be done, I brought in the considerations of the electrical design and a manufacturers persective of the problems and tradeoffs. You can no doubt achieve success, however, at what cost? I have invested M$ in projects only to find out they were not commercially viable.

I will hold my opinion until such time I can see comparative results and base my opinion on these. Until then we can only speculate.

Glad to see both of you taking a challange which should result is some real answers and not speculation. :clappp This is how technologhy is advanced.

I would gladly invest in kero start and a governor if it were available. :thumbup:

In the meantime we work with what we have........ and look forward to monitoring your progress

Bob

[Sara]

Thanks for the order, Peter! It was good to talk to you yesterday. I look forward to hearing from both you and Chris about the progress made on these projects.

It's good to see this sort of co-operation - I get rather tired of the mudslinging between Wren's and JetCat's customers. Yes, Jetcat are our main competitors, but that doesn't mean that every time I see Marcus Zipperer I punch him on the nose! On the contrary, we are polite to each other - I met Bob Wilcox at JetPower in Germany last September and we had an interesting conversation, at the end of which I offered him a piece of my homemade cake - which he ate, and it didn't poison him. Maybe our customers can get along politely now, perhaps Peter Wales and Chris Bergen can start a trend here.

Sara Parish
Wren Turbines

[v22chap]

Oh man oh man .. I was thinking that IRCHA was out this yr as money is really tight right now with the wife in her final phase of her masters of Midwifery / nurse practioners degree and having to quit work for almost 8 months to do clinicals ,,,,but now ... I just have to be there :thumbup:

# 1 to see this dual of turbines .... :hug:
# 2 to meet Peter in person :happyd :noteworthy :wow2:

[Greg Alderman]

Oh goody! I hope that I get to do some of the side by side comparison this year with the JetCat vs Wren...it will be fun to fly both...

Now that the bickering is over for the moment...I will put my comments in...most of which was documented someplace on line a couple of years ago...I flew the summer of 2005(maybe it was 2006...I getting old! OK...not quite as old as Peter but! :D ) anyway...what ever summer it was I had a Model Avionics "RevMax" on my Bergen and actually had pretty good results as long as I was only using it as a "limiter" and my normal headspeed remained under the "threshold"...if I set the limiter so it was "always" limiting (this was pretty much the desired way on a nitro setup) I would get a lot of turbine speed fluxuations...(if any of you ever lived near a military airbase...it sounded a lot like a fighter jockying the throttle on final approach) but strangely enough my head speed remained very constant and the heli flew great...but just the sound was aggravating to me...

I guess the bottom line is that it worked pretty much better than I expected...but I ended up taking it off the heli as it was just one more thing to mess with...

I also believe...that although a Governor is not needed for good 3D flight...I would be the first one in line to have one if ever offered by Wren...as I always tweak the throtle curve on the first flight of the day to ensure my headspeed in idle-up is 1675...

Greg

[lperagallo]

This came from a thread that I started in parallel to this one over at RR. The following is a post directly from Gaspar Espeill, the person that makes Wren FADECs. It comes from the same post on RR back in October. So hopefully, we will eventually get one. http://runryder.com/helicopter/t374971p7/ Hello guys,

A friend of mine commented me this morning about this thread, and I would add some comments:

1) Why the Wren TS don't have governor. Well, there are several reasons, basically I haven't got the feedback of that ir was so important, the ecu model that Wren use now don't support it, and that I'm not a heli turbine pilot in active so the tests are very complicated. This is going to change soon.

2) The need or not of the governor: Sincerely I don't know. I did fly helis 12 years ago (glow), and at this time nobody was using governors, so I didn't learned about the real utility of these devices, although I designed and tested one in my heli, but soon I lost the interest in playing with it and decided to fly more. I see the need of a governor on a glow engine, the performance of the engine varies from from day to day, so a device that control the engine is useful. But, in a turbine engine like the wren, where when you set the 81% of throttle always you have the 81% of RPM in gas generator, independently of the ambient temperature, humidity, etc.., not. Turbines are much more "consistent" in the throttle set/power delivered than glow/gas engines so that they can be flown with throttle curves reliabilly. Yes, a second stage governor make life much easier, no need of throttle curves, plug an play.

3) Understanding and limitations of a two shaft engine: Single shaft engines (glow, gas, PH3, belt driven etc) are much easier to regulate because the inertia of the system play as a stabilizing factor, the goal is to keep all the rotating elements, including the high speed ones with lots of inertia, at same speed all the time. Just need to throw a bit less or bit more of fuel to the engine to correct the tendency of to change its rpm. Plenty of time to do it, the inertia help us.
On a two stage system, things are much worse to control. First the ecu have to control 2 shafts in place of one. Two speed sensrs,e tc.
To change the power delivered, the gas generator RPM should change to provide more or less airflow to secondary turbine. What this means is that the inertia of the gas generator is playing against us for a fast and smooth control.
If the rotor is loaded, the RPM of the core engine should increase. If unloaded, rpm should decrease. There is a "lag" in to change the rotor RPM due to its inertia, so if the rotor is unloaded from max pich to zero in 0.1s, the rotor of the gas gen could take 1-2s to reduce its speed to the required of for zero pich. This will give invaribilly a acceleration on the rotor, more noticible as the diference between the speed in the changes in pich to the speed in change the core rpm.

The speed of that a turbine engine can change its rpm is determined by the inertia of the rotor and the combustion chamber design. A good design on which is posible to increase the fuel very fast without overheating and where is posible to lean the combustion abruptly without flaming out, is much easier to cotrol in fast pitch changes than in a slover system.

At this moment I don't know what percentage of the total power needed in a rotor is the diference between a zero pich and max pich. If large, it will be difficult to control, as the rotor of the gas gen will need to change a lot, if small, easier. I should do some tests first with a heli before writing the software.

Finally, if any of you have a "wish list" or suggestions of what a ecu of a heli engine should do, let me know. For example, the governed speed, should it be modifiable remotely with a secondary channel in three steps or linearly from a minimum to a maximum?


Regards,


Gaspar

[v22chap]

and if I remember right he called Chris and ordered a Bergen turbine bird to test a unit on so he would know what he had to do .:hug::thumbup:

[cbergen]

We quoted him for one, but he didn't order it.....

[Peter Wales]

Well, there are several reasons, basically I haven't got the feedback of that ir was so important, the ecu model that Wren use now don't support it,


Aha, so it's all Sara's fault :)

[Sara]

Aha, so it's all Sara's fault :)

Most things are, apparently. Good job I've got a sense of humour!

Sara Parish
Wren Turbines