Run in stand/dyno build.

[dwilfong]

Terry you can mix the channels on a 4 channel system so the needle would only be controlled when you want it to.
Did this on a boat to control the strut angle when you turned the rudder.
I will mess with a prototype and then post what I find out.
But it will need to be tested on a running eng in a controlled environment to confirm what it dose.
Now if some one could wright code that would be the bomb.

 

[Charles Perdue]

No need to build it yourself, maybe if you come across some info post it here? This is something I'm possibly looking at for down the road.



That's what I'm thinking exactly, it would "tune" the needle to keep a constant EGT as the other factors tried to change it. It would probably be best to have some sort of throttle position input as well so it only was "active" at full throttle.

It could richen the mixture when the boat goes around a corner, keep it from going lean at the end of the straight away, compensate if a little speck of dirt got in the needle or cooling system etc. etc. Plus you could travel anywhere or run in any air and the needle would be bang on.

Hmmmm....

The fly in the soup is that measuring the EGT and using it to control the mixture is two different things.
The major problem is as the mixture is leaned more and the EGT goes up, when it is leaned beyond the ideal mixture, any leaner and the EGT begins to cool as the combustion is not complete due to the lack of enough fuel to the amount of oxygen. This is when the engine looses power.
Been there and done that.....

Charles

 

[dwilfong]

So it would have to see the peek and when it goes over that and starts down it needs to reverse direction.
I think the 555 timer chip can do that.
Great input.
Thanks for the heads up.

 

[Terry Keeley]

Just talked to my Consigliere (Rudy) about this, he has a little Arduino experience and thought one of those could be programmed to do the job.

Imagine a circuit between your rx and mixture servo with a feedback loop that would maintain the EGT you set on the transmitter.

Hmmmmm....


https://www.arduino.cc/en/pmwiki.php?n=Main/ArduinoBoardNano

edit: Looks like it's already been done: Nano - Max6675 - Typ K Termocouple- Installation- Fehler im Monitoring

 

[dwilfong]

Terry I have all the hard wear to do this just need some one to show me how to put the codes together and up load them. Also what pins to use for what sensors and servo control.
I did spend time in the play ground but it is over my head.
Even looked at going to a group meetings of a club gust for this.


I did do some home work but other thing got in the way.
The bottom one is the 555 timer chip set up.

 

[Steve White]

Not to crap or throw cold water on this - great reading.

To work correctly, it would require TPS as well as EGT at a minimum. Demand -vs- actual performance and firmware that would probably ignore anything but a specific part of the time window at WOT.

 

[dwilfong]

Not to crap or throw cold water on this - great reading.

To work correctly, it would require TPS as well as EGT at a minimum. Demand -vs- actual performance and firmware that would probably ignore anything but a specific part of the time window at WOT.

The signal to the throttle servo is your TPS.

So the fly must have smelled the crap in the cold water and fell in then it was heated up to make soup?
Just asking for a friend.......
Sorry Terry I will leave you to your Dyno now.
Can not wait to see what you do with it.

 

[Steve White]

Not to crap or throw cold water on this - great reading.

To work correctly, it would require TPS as well as EGT at a minimum. Demand -vs- actual performance and firmware that would probably ignore anything but a specific part of the time window at WOT.

Add RPM to that as well. TPS RPM EGT outta get it done.

 

[RaceMechaniX]

Interesting. I looked at the manual Pdf Download | O.S. Engines FS-91 II FI User Manual (29 pages) and it's not clear if the unit adjusts the mixture "closed loop"? In other words would it richen the mixture if the airplane went vertical for example?

Looks like it might just have a red/green light for rich/lean based off rpm and head temp?

Terry, my understanding of the system is it is closed loop, but instead of using EGT's, it's using CHT's. CHT being more consistent and easier to monitor compared to an EGT sensor. EGT sensors in the exhaust stream have a short life with the higher temps, vibration and fouling of the tip with carbon and oil. I am sure the OS engineers likely developed the code using an EGT in their calibration and developed a virtual EGT sensor based on CHT, load and RPM. The throttle input was the load source and you calibrated fuel throttle, idle and stop on your radio. Back in my karting days the KT100 engines were mostly tuned measuring CHT on your Digatron display. Some guys did have EGT sensors on their karts.

There is a OS 60T carb on eBay: OS 60T FI Carb
Also the CHT temp sensor: OS Temp sensor

 

[Mike Rappold]

Real (model) world experience, just what I'm looking for.

Looking at the Pyromation catalogue here https://www.pyromation.com/Catalog/ProductCatalog.pdf I see a bunch of information in the 1st fifteen pages or so.

I'm thinking a 1/16" "exposed junction" with a 316ss sheath should work for the exhaust (pg. 12)?

For under the plug Mike Rapold used a solder lug crimped to an open wire thermocouple, any experience with that? Currently I'm using a thermistor with the Eagle Tree (resistance based) but it's not compatible with my dyno box.

Any idea hot hot the exhaust runs on our motors? Got any part numbers? Thanks!

I am using a EGT sensor from Pyromation. It is a 1/16 dia 316 stainless steel probe, shielded exposed junction MgO type K thermocouple. The probe is bent at 90 deg to fit inside the pipe. This can be ordered from the factory - custom order. I am using the EGT sensor mounted at the center of the barrel section and sensing close to the pipe's centerline. To hold the EGT sensor in place, it is a modified #10-32 brass screw with acorn nut to create a compression fitting.

On the CHT, I am also using a Pryromation TIG welded junction type K thermocouple. I use an electrical eyelet to create a glow plug washer to hold the thermocouple. The eyelet is cut down in size, bent and soldered to the thermocouple. The cooling head of the engine has to be modified a little to provide a pocket for the thermocouple to sit plus give clearance for a glow plug wrench/ignitor.

Both the CHT and EGT are feed back to an Eagle Tree thermocouple expander board. Using one of their data loggers too.

As an example, for EGT on a my set up on a 67 outrigger, the EGT is between 550-650 deg F. Will vary with conditions - tune, load, etc. I do find the CHT to be more useful for overall tuning. Kind of like getting the CHT in the correct range by varying cooling water flow, needle, head clearance, etc. and the EGT will follow.

Mike

 

[LohringMiller]

You might consider an oxygen sensor though I have no idea how sensitive one would be on nitro. Also oil would be a problem. Below is a system used on the stinger for testing gasoline engines.

Lohring Miller

 

[Wasted wages]

Is that the "California model" for testing exhaust emissions ?
Making sure your weed wacker motors cat convertor is still working properly ?

 

[Marty Davis]

The speed of the EGT thermocouple is also of primary importance to control the mixture control. EGT on one of your engines is FAR below what you would guess it would be. We spent a lot of time finding the correct thermocouple for our dyno.

 

[Terry Keeley]

The speed of the EGT thermocouple is also of primary importance to control the mixture control. EGT on one of your engines is FAR below what you would guess it would be. We spent a lot of time finding the correct thermocouple for our dyno.

Did you guys put the thermocouple in the header pipe? As mentioned I've read that kart/bike guys shoot for 3 X the bore from the piston face. Remember what sort of temps you were seeing?

With Mike Rappold's help am pretty sure what I'm going to order for EGT.

https://www.pyromation.com/Literature/Catalog.aspx
Looking at a 1/16" "shielded" probe that has a 0.01 sec. reaction time. Initially I was looking at a "grounded" junction with a 0.3 sec. time but figured it would be too slow, especially for a mixture control.

For the CHT I'm thinking this will work:

https://www.zoro.com/tempco-thermocouple-type-k-trw00113/i/G2205183/

 

[Terry Keeley]

Been workin' on the NCBS (no contact breaking system)

 

[RaceMechaniX]

Slick magnetic brake Terry. Be prepared with a blow gun to cool off the disc. Your 30lb flywheel is going to have a lot of energy to dissipate in that small of a disc.

I modeled your flywheel quickly assuming 6" diameter and 32lbs. It has a moment of inertia of 0.82lb-ft^2. At 20kRPM that results in a rotational energy of 75.8kJ of energy. At 30k, it bumps up to 170kJ. Depending on how quickly the magnets slow down the speed, that's a ton of heat to dissipate in that disc.

Assuming that disc is aluminum with a mass of 0.5kg, it will heat up about 157DegC braking from 20kRPM. At 30kRPM the same disc will heat up 383DegC. Toasty!

 

[Wasted wages]

Gotta ask...why such a heavy flywheel ?
I really don't think our little engines can spool up that amount of weight very quickly, can
they ? Seems like it would cause undue stress on the motor and drive line that weren't real world numbers. just asking..

and if something snaps in the motor at high rpm, kiss it goodbye.... whereas a prop would come to a stop rather quickly...with only the engine flywheel as the largest mass to slow down and stop..

 

[Terry Keeley]

Slick magnetic brake Terry. Be prepared with a blow gun to cool off the disc. Your 30lb flywheel is going to have a lot of energy to dissipate in that small of a disc.

I modeled your flywheel quickly assuming 6" diameter and 32lbs. It has a moment of inertia of 0.82lb-ft^2. At 20kRPM that results in a rotational energy of 75.8kJ of energy. At 30k, it bumps up to 170kJ. Depending on how quickly the magnets slow down the speed, that's a ton of heat to dissipate in that disc.

Assuming that disc is aluminum with a mass of 0.5kg, it will heat up about 157DegC braking from 20kRPM. At 30kRPM the same disc will heat up 383DegC. Toasty!

Ya, one of my engineers mentioned that but we all thought he was crazy, lol.

In practice it'll be to slow the wheel from the peak (28K?) back to a high idle of around 12K to get ready for another pull. We'll see, I'll probably need to rig an electric fan on it or something.

The disk is part of the coupling between the shaft and wheel so I don't want it to grow much either...

 

[Terry Keeley]

Gotta ask...why such a heavy flywheel ?
I really don't think our little engines can spool up that amount of weight very quickly, can
they ? Seems like it would cause undue stress on the motor and drive line that weren't real world numbers. just asking..

and if something snaps in the motor at high rpm, kiss it goodbye.... whereas a prop would come to a stop rather quickly...with only the engine flywheel as the largest mass to slow down and stop..

Looking for 3-500 rpm/sec between 15 and 25K or so: http://performancetrends.com/Calculators/Engine-Inertia-Dyno/Engine-Inertia-Dyno.php

Engineering added a centrifugal clutch and one-way bearing in case of engine seizure:

Above morphed into:

 

[LohringMiller]

That oxygen sensor setup was developed by a South African who builds hot saws among other small two strokes. About as far from California as you can get. I also think Terry's flywheel is a little big. Our 5.13" diameter x 3" long flywheel managed to load 11cc nitro engines enough that they melted pistons. We mostly tested gasoline engines from 2 1/2 hp to almost 12 hp at up to 25,000 rpm.

Lohring Miller