Malorie's Gasser Throttle setup

[cbergen]

Here's Mal's setup, In her own words,

After slamming my gasser around for a while, I got tired of overspeeding the head at times. I'm running the GV1 with the Stator Gator sensor. It was most noticeable during big push-outs to inverted where my headspeed would come up to around 1900 to 2000. I would need to either load the rotor system again or hover for 5 or 10 seconds for it to come back down.

I decided to try an experiment that seems to have really worked out nice.

My thinking was that, unlike a glow machine, the butterfly valve carb on the gas machines is not linear. It tends to have most of it's change at a nearly closed position and very little change from about half way open to full open. I figured the GV1 was having trouble with the minute adjustments required to maintain a good headspeed as I unloaded the rotor system.

So I changed my throttle linkage to include as much mechanical expo as I could get. This would give the GV1 better resolution at lower throttle settings and less at higher settings which in effect made the throttle much more linear.

During test flying the setup, I tried my best to overspeed the head. The GV1 was right on top of any change. The worst it got was a minor overspeed during big push-outs to inverted. The GV1 would almost imediately fix the overspeed though, very much like my glow machine.

This also changed my throttle curves from a "U" shape to a "V" shape which tells me that the throttle is now very linear.

Try it out, you'll like it.
Malorie

Life's a journey, NOT a destination.

I set my arm on my servo so that at full closed throttle it is pointing nearly straight down the linkage and a full throttle it is pointing just past 90 degrees. Then I set the arm on the carb so that at full closed it is at nearly 90 degrees and at full open it is pointing almost straight down the linkage.

This way at near closed position the servo has to rotate quite a bit to get little rotation from the arm on the carb. At near full throttle the servo only rotates a little to get a lot of rotation from the arm on the carb.

This setup really make the gasser act a bunch more like a glow machine as far as throttle curves go.

Have fun, I really like this setup.
Malorie

If you are having any difficulty with this setup, it may be that your initial mechanical setup is incorrect. Hard starting or having to put your throttle at an extremely high setting to get it to start may require starting over from scratch.

From the Observer EB manual,

Setting up the throttle requires some math. Make sure the throttle curve in your radio is a straight line from 0 to 100, no curve just yet.

Throttle ATV should also be set at 100%, both low and high.

Place the throttle trim all the way down, and stick all the way down. This is the engine shut off position. Now try to place the ball link onto the ball on the throttle arm, with it all the way closed. It will probably be off a little bit. Adjust the low ATV to the amount necessary to pop the ball link onto the ball.

Now go to full throttle, leaving the trim all the way down. Again try to place the link onto the ball. You will need to open the throttle on the carb, by hand, to its wide open position. Adjust the HIGH ATV this time, to the amount necessary to pop the link onto the ball.

Figure the difference between the high and low numbers on your ATV’s, for instance, the low is 95 and the high is 85. The difference is 10. Divide that number in half and add to the lower number, subtract it from the higher number, so you end up with 90 on both high and low ATV’s. Now adjust the length of the throttle pushrod to snap on the ball at both the high and low ATV. This will give you a perfect linear throttle setup with half throttle at half stick. Using a governor such as the GV-1 DOES require the ATV's to be at LEAST 100% or higher, so it may be necessary to move the ball on your servo wheel IN a little bit to achieve higher numbers.

Once you have this type of setup, ensuring at least the radio is configured properly, THEN make the adjustments as noted in Mal's setup.

[Magenta]

Thanks for the post. I was just about to start hunting for it and this saves the time

[Pinecone]

FINALLY.

I see something I have setup wrong, I set the carb to be 45 degrees at low and high throttle. Need to change that. And that would probably help with my hover headspeed. I was getting the right headspeed at 0 pitch, but it would start to increase as the pitch did.

[Cletus]

Yup, my carb was setup at at 45* too, guess I will have to change that likewise. Just when I got the idle/engine-cut trim setup nice and been spooling-up on the front lawn every afternoon freaking-out the neighbors ....She gets light on the skids just a bit past half throttle.
Once that's done, I'm ready for the Maiden on Saturday.
BTW Heard from Brian at Heliproz today, you were right, it was the big move that had them disorientated. They advised that I return the servo for an exchange. So FedEx it goes tomorrow.

[F6Hawk]

Originally Posted by Cletus

BTW Heard from Brian at Heliproz today, you were right, it was the big move that had them disorientated. They advised that I return the servo for an exchange. So FedEx it goes tomorrow.

Same here. It took a few days to get an email back from them, and they apologized for the delay, but they are trying hard, it seems. Moving is tough on anyone, especially a business.

[Pinecone]

Switched to the 90 degree carb arm, and need a higher mid stick throttle setting for 1650. But still have to dial down the upper range to keep the RPM steady. I wonder if the Max engine with 13 tooth pinion might not match as well as some other setup.

[Cletus]

Got mine done, but to achieve idle/cut using endpoints, I ended-up with the servo arm down at a 45* angle. Will get back to all of that later, just hoping all this rain holds a bit as we're ready for the Maiden today with the hopes of tweaking some setup parameters. Been running the engine and spooling-up the rotors in the yard over the last three evenings, just to the point of being light on the skids. Headspeed seems high, but we'll know for sure today when my buddy tachs it. The canopy and tailfeathers are at the airbrush dude and hopefully that will be completed by next weekend. Got the CPII connected-up and working the way it should, it did not like my custom mount, so I had to revert to a more traditional installation arrangement.

[Pinecone]

I found, with the throttle blade fully closed, with the setup that Mal shows, that I need almost fully high trim to start and idle. So I am working towards and end point that will idle at mid trm, but still shutoff reliably at full low trim.

I am going to install my Eagle Tree to get some RPM readings this weekend.

[Cletus]

Originally Posted by Pinecone

I found, with the throttle blade fully closed, with the setup that Mal shows, that I need almost fully high trim to start and idle. So I am working towards and end point that will idle at mid trm, but still shutoff reliably at full low trim.

I am going to install my Eagle Tree to get some RPM readings this weekend.

Eagle Tree eh, I'd love to own such a system
I really need to get me a tach though. I bought all the parts to build one (as I like the idea of a knob instead of pushbuttons to set the strobe rpm) but just can't find the time to put it together.
I just fiddled with the throttle some more. But will leave it as is for the time being. To really dial it in, as per Mal's setup, I need to turn the servo around (wheel facing forward) so that the linkage would adjust properly, right now both links are pretty-much turned all the way in. If I really can't fly today i'll probably end-up doing just that ......It's raining bucket-a drop here
Engine starts real nice though, second pull when cold and first pull when warmed-up

[Pinecone]

They are under $100. No reason to not get one.

For today, I used a piece of servo tape and some masking tape to attach the magentic sensor to the case. I think I wll do the same thing for the gov sensor.

I have a Sky Tach, but no one at the field can seem to use it properly.

[F6Hawk]

I got one similar to the Sky Tach, it's the Bantam version that does servo testing, too. I love it, but it sucks that it takes 2 people to make it happen. On another note though, I gave it to the wifey, and she figured it out in about 30 seconds. Surely other RC buffs at the field can figger it out? If not, tell 'em another guy's wife got it first try, THAT should motivate them!

[Pinecone]

That might work.

[heli junky]

what kind of cure is everyone using with this setup? 0 50 100 100 50 100?thanks

[Cletus]

Originally Posted by heli junky

what kind of cure is everyone using with this setup? 0 50 100 100 50 100?thanks

That's the suggested starting point and where I'm at. Next flight, the tweaking begins.

[Cletus]

Originally Posted by F6Hawk

I got one similar to the Sky Tach, it's the Bantam version that does servo testing, too. I love it, but it sucks that it takes 2 people to make it happen. On another note though, I gave it to the wifey, and she figured it out in about 30 seconds. Surely other RC buffs at the field can figger it out? If not, tell 'em another guy's wife got it first try, THAT should motivate them!

I just ordered the Bantam myself. Looks like good value and multi-functional.

[heli junky]

thank you iwasnt shure.dave

[Pinecone]

Yes, you will have to tweak. On my Intrepid (non-EB) with a Hanson 3D Max engine, I had to tweak the mid point up a few points and then lower the next couple form linear to keep from overspeeding.

[heli junky]

thanks pincone,i watched all youre videos on the build great job

[F6Hawk]

Originally Posted by Cletus

I just ordered the Bantam myself. Looks like good value and multi-functional.

Just out of curiosity, what'd you have to pay for it? Got mine for about $90...

[Cletus]

Originally Posted by F6Hawk

Just out of curiosity, what'd you have to pay for it? Got mine for about $90...

Only place I could find it in stock:
www.commonsenserc.com
1 x Bantam Check Master 2 - Plane and Heli Tester (BAN-CKMAS2) = $109.95
1 x Bantam Temperature Sensor Cable (BAN-EAC110) = $9.95
Sub-Total: $119.90
United Parcel Service (UPS Ground): $10.40
Total: $130.30
It will get to my Miami, FL forwarding address on the Aug18 and to Trinidad a few days later. I'm off to Canada for a week come Aug 21 it should be here when I return.