Cox .010 r/c with commercial accessories

Thanks, Levent,

in fact my 010 with the PET throttle control was not working at its best in that video, and I have not corrected it. The lowest rpm with the PET is definitely below 10k...the highest, well, like any 010 without any throttle device, near 27k...on that freezing winter day in my garage with only 20% nitro in the fuel, it did not go faster than 23.3k

balogh wrote:Thanks, Levent,

in fact my 010 with the PET throttle control was not working at its best in that video, and I have not corrected it. The lowest rpm with the PET is definitely below 10k...the highest, well, like any 010 without any throttle device, near 27k...on that freezing winter day in my garage with only 20% nitro in the fuel, it did not go faster than 23.3k

András, did you mention that it can be adjusted below 10,000 rpm? Is it really the case? Well, in my case at 12,500 rpm the engine hardly turns and almost stops, it would be interesting to see your video with that range of gears.
I'm doing a new video on my Cox .010 r/c max and min turn ranges, will post soon.
For that reason I wanted to see what range the commercial r/c controls are in.
Thanks.

Mauricio,

I have the PET manual -  issued by its inventor the late and great Mr Roger Freiheit - in my Budapest home, where I will return from our Balaton lakeside house on Thursday, and scan the page where he writes about the range. This is the fastest information I can get, and I tend to believe him about the low idle speed, as I got to know him as a very credible and meticulous COX expert. Later this autumn I can repeat my own bench test with the PET and see the actual lowest idle speed.

The thesis of his Proportional Exhaust Throttle (=PET) is based on the different thermal expansion of the brass throttle and steel cylinder. The brass throttle contracts more than the steel cylinder when the engine runs at low temperature in idle, and the contracted throttle seals very well, thus its idle is expectably, really low.

balogh wrote:Mauricio,

I have the PET manual -  issued by its inventor the late and great Mr Roger Freiheit - in my Budapest home, where I will return from our Balaton lakeside house on Thursday, and scan the page where he writes about the range. This is the fastest information I can get, and I tend to believe him about the low idle speed, as I got to know him as a very credible and meticulous COX expert. Later this autumn I can repeat my own bench test with the PET and see the actual lowest idle speed.

The thesis of his Proportional Exhaust Throttle (=PET) is based on the different thermal expansion of the brass throttle and steel cylinder. The brass throttle contracts more than the steel cylinder when the engine runs at low temperature in idle, and the contracted throttle seals very well, thus its idle is expectably, really low.

Thank you Andrew for your reply.
I do not doubt his word and what the manual contemplates there. I'm surprised that the engine can work below 10,000 rpm! It's something that I find incredible, but if the manual says so...
I keep doing my tests, even changing the position of the fuel tank, higher, lower, always the engine vacuuming.
The manual says that it works below 10000 rpm, it contemplates a traditional Cox Tee Dee .010, that is to say with its own tank or rear plate and therefore always sucking the fuel, NOT with a balloon that sends pressure to the venturi... should see what happens.
Well friend, it's not urgent, but if at any time you want to see what really happens, it would be good to check what the manual says and what the tests actually turn out after. I submit that a Cox .010 below 10,000 rpm is incredible!

I haven't checked the rpm but seems slow it was super cold that day i made the parts m'y self

David, thanks for your input but:
You should get the highest rpm possible and the lowest possible without having the glow plug clip attached. That is, you start your engine, tune it as much as possible, remove the clip from the glow plug and begin to measure the "maintained" low rpm, that is, constant, let's see what happens?

In fact, only the positive wire was connected to the cylinder the negative wire held in place with the thumb when the engine starts it is released A slight change of position and I activate the valve with the other hand It would be easier with the motor install on something my motor supor for this little motor its my hand in this test But yes it's true the second time I keep it connected its so cold that day   f:lol!: this is the first time testing it soud To ritch in this video But if I connect it turns on the engine gains rpm And we can see the difference better I should test it on an rc airplane model in the hot sumer https://youtu.be/jFwKgJv-vM8

Here I made video captures of my Cox .010 r/c engine running.

High:




Short:




Máximas rpm: 27330
Minimas rpm : 13230

Below 13,200 rpm, the engine stalls.

Mauricio and all those, interested: here is the link to the Proportional Exhaust Throttle (PET) invention patent of Mr Roger Freiheit:

https://patents.google.com/patent/US6748908B2/en



It is freely downloadable as a pdf file, here: https://patentimages.storage.googleapis.com/08/91/23/5b2780e28f5666/US6748908.pdf

And here is his statement in section 2 of the patent description, for the rpm range achievable with the PET:

"The disclosed and claimed embodiments of the invention are directed to a control system for a miniature engine having individual cylinders with at least one exhaust port to exhaust gases from the cylinder that achieves controlled speed range of 6,000 rpm on idle to 30,000 rpm on full speed."

Although no particular miniature engine brand is referenced, it is obvious that he worked out the patent with experiments on the 010 TeeDee.

Thank you Andrew for your contribution.
I have no authority to question that article, I want to be very cautious with my comment, having said the above, in my experience of serious tests and with all the steps that this implies, I deduce that a Cox .010 engine in normal conditions of use, that is to say , with fuel up to 30% nitro, with its own or additional fuel tank, that works by suction of air and fuel, with the Cox propeller indicated for that engine (without modifications) and in operation by the glow plug, without being assisted by additional electrical power, in ambient conditions of 25 degrees temperature and 34% humidity, in a closed space, that is, without the aid of additional wind in the line of the running engine, the Cox .010 taken to its maximum revolutions with a regulation ring, it can turn at peaks of 27,000 / 27,300 r.p.m. and from then on, and always with the same carburation, reduce the revolutions by throttling or closing the exhaust gas outlets of the cylinder (two), the engine will not be able to keep running below 12,000 rpm. There is room in the test for some variant to have some margin of difference, but it will never be able to be regulated at 10,000 rpm.
If someone or yourself wants to try this accessory, it would be very valuable to find the true point between what the manual says and what actually happens.
All my comments, deductions and experiences are serious within the framework of respect for everyone, including, of course, the author of the manual.

No problem Mauricio, I just posted a citation from an official document...but seeing is believing..I have no way to verify the low idle of 6k rpm except by a bench test of my own...I also doubt if 6k is achievable, but will see in my own test.

I think that material selection is important

From patent page:

Levent, amigo!:
Yes, the type of material to use is a separate issue.
Depending on the metal, the expansion will change and for that reason, the seal between the cylinder and the regulation ring will change, for that reason, and also in my personal experience in Cox .020 engines, you can see (in the photo) that the The bronze ring has a larger section than the steel ring, that is because with the same section, the bronze ring dilates more and therefore seals less, which means that the engine's revolutions do not drop, on the contrary, they remain high.
For this reason and I repeat, if the engine is tuned from the needle to its maximum revolutions and then the ring begins to turn, the revolutions drop to a value that in the case of the .010 is well above 10,000 rpm. before it stops.
The problem of maintaining such a low idle (let's talk about 10,000 rpm), happens that the engine no longer has suction force to extract fuel and when lowering the revolutions, the temperature of the cylinder and glow plug lowers, these factors act together and the motor has no way to work. Now, if at that moment you place the clip on the glow plug with the battery and assist that glow pug, it may keep going for a while longer, but it will still stop, because the other factor acts, which is, as I mentioned before, that the engine does not have enough fuel suction force due to low rpm. And if in the last case you raise the tank to help the engine to receive fuel, then it suffocates, because the glow plug and the cylinder do not have enough temperature to keep the explosion alive.

Cox Tee dee .020 r/c engines
Ring in bronze and ring in steel. Note that the bronze ring has a larger section than the steel one, this is to keep the expansion even with the cylinder, which is made of steel.

Hi Mauricio, perhaps Andras try it with a normal fuel tank such as .010 own fuel tank. I think that you are right and balloon fuel tank is a need for under 10K revs.

Very interesting discussion , I have read all the info when Mauricio made the throttle rings and don't remember the differences in the metals being mention . Does make since with all metals expanding differently and trying to keep a close gap and still turn at lower RPMs , that puts trial and error and success to another level . we need a butt scratching icon LOL

In my opinion the idea of thermal expansion is nonsense. Take a second to do the math and consider the actual values of linear distance in question. I think the components would be fighting tolerances and finish of the cylinder OD above all else. If anything, the method of assembly allowed individual fitment to the cylinder. Wasn't there a warranty stipulation that these not be disassembled? I don't remember speaking with Freiheit, but I did work in the hobby at the time and he tried to get us to distribute his product. At the time, we were working on bringing small electric brushless to market. Small engines were on the way out, why spend the time and money for a patent? Get them out and sold before the market disappears. I think the concept of thermal expansion was solely to make it unique enough to get a patent. Did it really idle to 6000RPM with the 3x1.25 prop?

Why would Cox have gone to the trouble of grinding cylinders and throttle sleeves?

Hi Greg, I'm telling you about thermal expansion and my experience.
In the video that I leave here, it is a Cox .09 Medallion, to which I made a control ring, in aluminum alloy.
The ring dilates and takes longer to shrink than steel and for this reason there is a delay in the engine turning down when one puts it from the radio control to idle.
This is NOT observed in the flight, but at the end of the video and on landing, you can hear the engine still running, this is because the ring is dilated with respect to the cylinder and it takes a few seconds to seal again, just when it drops from temperature.
In conclusion, with the aluminum alloy rim, in this case, you do not have an immediate response from idle after a period of use at full throttle.