Governor for a Wren

[Bell Bloke]

Hi Folks, just curious, but how close would you expect a governor to track the headspeed?

I do it the regular way, with pitch curves on the Wren with a 30lb model and 140,000 on the engine.
I find that I can keep the headspeed inside +50 to -50 rpm on the head doing hard climbouts and rapid decents. I set up the heli using a small camera to monitor the flight and make adjustments when I land.
Please note that I don't fly with idle up, it's all on the stick and at no time does the turbine unwind even on fast decents. I find that I get the worst variations when I punch in the pitch hard and then flat pitch it quickly, however even then I stay inside the 50rpm threashold. I find that seeing an actual video of the flight and seeing the rpm real time so to speak saves a huge amount of time in setting up.

Anyway back to my original question, how close can a 2 stage governor track the headspeed?
Many thanks, Bell Bloke.

Ps, can supply onboard footage of my 30lb machine in action if necessary, It is very revealing.

[bcook01]

Bell Bloke

how close would you expect a governor to track the headspeed?

That is the million dollar question. Would enjoy seeing the video if you can post it. I am surprised the head is holding within 50 rpm which is quite respectable.

What are you using to measure the head speed?

I would question if you could do it much better than 25 rpm worst case conditions with a governor. The governor would probably be better at dealing with fluctuating temp/humidity/altitude/loading/etc. variations from day to day ops. Again there is no real confirmation (data) available for the governed single stage turbines.

A logger on a few flights might be able to generate the information........

tnx for the info

Bob

[Bell Bloke]

The video is at my friends, I will get him to post it here for me in the next couple of days if he has time.
On it you can see the very rapid gain in altitude from 5 feet to 300 feet with only a slight loss in headspeed. you will also see fast forward flight and quick decents in these the rpm holds very steady. Under normal flying the rpm hardly deveates at all.
The rpm is measured by a boom mounted guage which the camera is pointing at and this also gives an overveiw of the flight, although the camera is pointing backwards it shows a good view of the flight the head rpm and the sound allows you to hear and observe the engine under load and off load.

[Peter Wales]

I have started to do my bit. I have modified the Jetcat front end to read the Wren magnets, rewired the starter and glow plug connector and fitted the output speed sensor to the gearbox. Unfortunately the fan I am using is out of a crashed heli and is very bent so I daren't run it up too fast but it idles nicely. A quick blip of the throttle soon had it spooling way up, but I hadnt set any max rpms in the ECU as I am still waiting for the instructions for the Cuatro kit which Wren sent me.

Here's a video of it starting and spooling up. At first, watch the air bubbles in the fuel line and see how the engine winds up when they are gone. Then the sound seems to disappear. This is because at idle, the sound beats nicely with the sampling rate on my camera so you dont get to hear much.

http://scalehelicopters.org/wrentest.wmv

Now I get to do some tidying up and make it safe to fly before I fit it into a heli.

[v22chap]

Way to go Peter ...by the way that harmoic with the camera was really hard on my old ears before I got to the volume knob :smokin:

It looks like it was holding it pretty darn close ... looks like you have done more than Gasper ,,as last I knew he hadn't order a bird (from us anyhow ) to do testing with a governor .
I know a lot of guys say you don't need it and I don't want to start another typing war ...but I had an experience last yr ...that I think warrants a governor and I think I just heard of another one that was even worse than mine .
I don't want it to control head speed ... only just to keep the fuel pump system in line as I am pretty sure that was what caused my problem ,, as a new fuel pump seemed to stop it ....well for a few months any how and then it started to creep back in .
Now maybe it was my setup ...maybe my fuel ...who knows for sure .. I am a newbie to turbines and also know that some oldies don't have all the answers yet either ,,,, but I think it would be nice to have the option available for those of us that seem to run into this problem area .

Keep at it Peter and thanks for taking the time to do this and share ,,now get back to testing :whip ;) :)