Taurus Flyer

CW,

I did think about the situation and there are some facts to think about, especially engines without ring?:

Quality of the piston and liner after about 500 flghts, maybe when the mixture is lean a less good combination does overheat the engine in shorter time because the distance between piston and liner is more!
Other point of which I often think is starting in cold situations.
I do preheat the engine with hot water, than I have always a higher temp of the liner and not the piston.
When people start a cold engine with electrical starter motor in an environmental temp of <14 degrees Celcius, the engine does for a while work as an aircompressor and the piston gets a higher temp because of this compression of air in the crankcase, untill the fuel evaporate. Is this true? What about the piston and liner fitting?

So there are some reasons that there can be problems after 500 flights.

Other facts to think about, but these do not relate with the number of flights.
Barometric pressure. Relative humidity, temp. etc

Example: The temp the fuel evaporate in the needle valve is 65 degrees C, 148 degrees F and that's not a high temp!!!!.
The temp of the needle valve assey depends of temp. of the fuel and the temp of the crankcase but also the FLOW of the fuel and that is less in mid range than with full power.
So the flow is the cool liquid for the needle valve!
Maybe that is the reason the engine quits in mid range!!! Higher needle valve temp.
Also the same story about barometric pressure.

A lot of facts we can think about and it is guessing for a lot of them but this summer I will continue to know more about these.

Cees

CW

Taurus Flyer,
You make some valid points. In the case of my engine the liner and ring were new and because it is winter here the temperatures were around 18 C. The engine has run quite happily on 40 C days during summer so I don't believe overheating is a problem normally. There is no doubt in my mind that the mid range stoppages were lean. The plugs were damaged- and will not run the engine in its current state. I put that down to the carby.
Nathan started this thread to sort out his problems so I wonder if he is having any success?
Cheers,
CW

Taurus Flyer

CW

Because there can??? be a reason the engine quit in midrange, because there is less flow through the needle valve, so higher temperature of the needle valve, there is still one "tip" I can give. Not a solution but a "tip".
Try to find a second needle valve assey.
I did use a needle valve/sprai bar of a Webra carb. for a short period, expermental mounted near the OS Max carb. and did fly without problems.
With this "tip" maybe???? you discover a normal midrange of the carb.
If you do continue have problems in midrange with a separate needle valve and use a pump, I would try to lower the pump pressure, but I do not have experienced that.

There are two keywords in the whole situation:
people think there is air in the connection between backplate mounted needle assey and carb
people think about leakage so want to mount new "O" rings.


When you use these two "thinks" in one message I say, think about this "tip"
(the separate spraybar of a Webra carb not even hás O rings!)

For my OS Max I do use a non return valve after the exhaust tap and a tank pressure controller after that valve.
I reduce the tankpressure as low as possible and necessary.
When I read all the messages about pumps, I never read about measuring the pump pressure, while that's so easy and most important!!


Cees

Taurus Flyer

CW,

I do not hear of any success so we need some more pressure on the vessel!
I think “Also the same story about barometric pressure!�, was too short!!!

I did look for a while for a clear explanation of the barometric pressure and the influence on our problem.
In the diagram picture 1, the red line is the normal boiling situation with barometric pressure 760 Torr so boiling temp is 65 degrees C.

Example!! Only to show!!
When the fuel pressure is for example 500 Torr (carb vacuum is minus xx Torr and on a high flight level!!) the evaporation/boiling temp is 50 degrees C is 122 degrees F.
The 500 Torr is the absolute fuel pressure in the "carb sucking moment" in the connection between the backplate mounted needle valve and the carb, so barometric on flight level, minus sucking pressure of the carb!!!

Conclusion!!
When there is a day (and it did happen!) with a low barometric pressure, you can have a bigger change for evaporation (boiling) on any higher level than ground level!!!!!

(I use barometric pressure measuring for flight level measuring in video planes, these are facts!)

This can be a very, very important conclusion for all the problems I hear about the quit of “backplate mounted needle valve feeded normal crankshaft ported glowplug engines�
That is also the reason for me to use the engine with enlarged bore carb, reduce of vacuum and reduce of drag and more power.
The constant ratio does give the possibility to use fuel without castor oil so a bigger amount of fuel and power.

When somebody has more information, let me know, I am interested, because these are all my own conclusions I work with!

Cees

wessco

My Feedback: (7)

Where do you find this OS 1.60 cookbook?

Taurus Flyer

wessco,

I cannot answer your question, I only did research in the past for the backplate mounted needle valve on an OS Max. because I did have (main) ballbearing problems and I did hear other people did have also.
That was why I did ask if the threadstarter also did use a "backplate mounted needle valve".
It would be interesting to see a picture of that engine set-up.
See how effective the "crankcase" ventilation is in the engine room of the "Cookbook?".

BTW
After a hight temp quit, the heat (+200 C ?!?) of all the head-, piston- , lining- and exhaust metal is divided over the metal of the crankcase also, that already can have a temp of 100 degrees. A simple calculation gives and total engine temperature of 166 degrees C. High enough to "exchange the ball bearing".
Only ventilation of the crankcase will lower the end temp of maybe 166 degrees.



Someone else can answer the question?

Cees

NJRCFLYER2

My Feedback: (42)

Nathan, sounds like your engine may be due for some additional maintenance. BTW, what's your definition of "tuned perfectly"? No disrespect meant here, but to some people, that's an engine screaming at the highest RPM it can attain before launch. You always want a slightly rich setting, where a quick pinch of the fuel line at full throttle results in a momentary RPM increase. If that's not what you're accustomed to doing, you will save yourself future grief by adopting that practice. The best hint I got was from the spool down behavior, which strongly suggests that it is going lean on you as the temperature climbs during that first minute of flight and things expand in the case. Very often this behavior reveals a bad bearing. As far as things to do besides making sure that nothing is clogged in the carb:

1. Change both bearings. Normally the rear bearing is the culprit, but you may as well do both. Best bet is a stainless steel replacement for the main bearing, or a rubber sealed bearing as a 2nd choice. Rubber sealed will eventually wash out the grease inside and will generally not last as long as the SS. If using rubber sealed, best bet for an after run oil is plain old castor, to avoid damaging the seal. Some after run oils may damage the seal. Do not replace with the standard factory main bearing, unless you like changing bearings often.

2. Check and see if your ring is worn out. Also check carefully to see if the ring is getting stuck with crud. Clean and possibly replace as needed. You can clean the ring groove without removing the ring, but once removed, be sure to change the ring. While you're at it, see if the liner and piston are varnished up. A very light varnish is OK, but you may as well clean it up anyway.

3. Clean up the top of the piston and the dome of the head to get rid of the carbon build up. As carbon builds up, it effectively reduces clearance between the piston and head and changes combustion behavior, often leading to or at least contributing to symptoms such as you've described.

Your pump is probably still fine, because you're not describing symptions of pump weakness in long verticals, but don't don't overlook the possibility that it has reduced pressure output a little bit over time. I would not tamper with that until everything else above has been eliminated as a cause. It sounds like your engine is due for some maintenance first and foremost. You may have some other items due for replacement soon for peak performance, but I would not start with them to address the symptons you describe. Possibly a piston/ring/liner set is needed, but I would not go there unless the compression is way down with a good ring installed.

Good luck!

NJRCFLYER2

My Feedback: (42)

Nathan, one other thing to check that can sometimes be a problem is the pipe. Sometimes they get enough desposits to mess with the settings as you describe. Also, it's possible you have had something fail in the pipe. I have had that happen in a couple of older Aeroslaves. The newer Aeroslaves are supposed to be better as far as baffles shifting around inside. The stuff I previously described for engine maintenance is most likey how you willl solve the problem.

F-4

To all you fellows running OS 160's with a pipe set up according to the OS 160 Cookbook:

I am having trouble with breaking headers right at the first bend near the engine. Have sent Karl Mueller emails for a replacement over the past 3 weeks but no response. Does anyone have another source for a 160 header to an Aeroslave pipe? Thanks.

John

lodomjr

My Feedback: (6)

John,

Are you running the extra pipe joint and two couplers? If you are not this is the reason the headers are breaking. The extra coupler allows more movement and keeps the header from breaking.

Larry

F-4

Larry,

Thanks for your reply. I have run it with one coupler only, 2 couplers, front of Aeroslave pipe restrained and unrestrained. So far 4 breaks on 2 different headers. The second, older header, broke on the 4th flight with 2 couplers. Am using Octura high temp coupler material which is very stiff...I think. I also have a Hyde Firm Idle engine mount, no nose ring. Still need a new header to try the 2 coupler set up again.

John

wessco

My Feedback: (7)

Just wondering again...where is this OS 1.60 Cookbook?

d_bodary

My Feedback: (85)

It was listed in the K-Factor, couple three years ago

wessco

My Feedback: (7)

man...that don't do me any good now.....

jonlowe

My Feedback: (12)

Here it is, with the addendum. Be sure to read both parts. Right click the attachement here, select "Save as" and CHANGE THE FILE NAME EXTENSION from .txt to .pdf.

jonlowe

My Feedback: (12)

A couple of things I found since the articles were written:

The biggest problems I hear about with this setup is that people don't follow it EXACTLY. [:@] As an example, people gloss over the part about presetting the idle mixture screw on the carb, and wonder why the engine immediately floods out at idle. Then they start screwing around with pump pressure. Follow the article exactly, and you won't have problems.

Between runs, leave the carb in the fully closed/throttle cut position. This prevents fuel from siphoning into the carb and flooding the engine.

The best prop I found to use with the 1.60 and a pattern plane was the APC 17x12W. These can be bought from Central Hobbies. Better throttle response, better verticals than any other prop I tried.

The engine starts easiest by handcranking by backflipping it against compression. When cold, open the throttle fully with the glow clip detached, and choke the engine with your finger until your finger gets wet. Close the carb, and flip the prop a few times to distribute the fuel. Then attach the glow clip and backflip it to start. After the first start of the day, a single backflip should start the engine.

After starting the engine, ALWAYS take it up to full throttle and hold it there for a few seconds BEFORE disconnecting the glow clip. This will prevent the engine quitting at throttle up. Helps burn oil off the plug and get it to full operating temperature.

I started using Octura boat couplers in the 3/4" and 7/8" sizes. These were the the longest lasting I found. You MUST use them with a two coupler/extension setup as described in the addendum. You MUST support the pipe at the front end to prevent header breakages. The couplers are hard to find. Graves RC in Orlando sometimes has them. Octura doesn't seem to have a web presence at all, and not even a phone number!

The pump is almost NEVER the cause of problems, and I rarely changed the pump pressure from the factory setting. If you have problems, look elsewhere. I never had a pump fail.

I tried a couple of different carbs with the engine, and got increased RPMs, around 200 to 300. The old OS .61 ABC RFP carb works well, as does the OS 1.40 RX carb. You have to drill and tap them for the screws to hold them onto the engine.

The stock crank can and will break at the rear of the intake port window from a sharp machining edge. I radiused the sharp corner with a Dremel and polished it. I had three break in one year using an APC 18.1x10W. All three had exactly the same failure, and the pieces were so matched they would almost intechange with each other. I started radiusing the port after that, and stopped using that prop at the same time, and had no further failures. The 18.1x10W is a heavy prop, which I think exacerbated the problem. The 17x12W turns out to be a better match for the engine anyway.

It turns out that with the pump, you can use normal medium fuel line. The large line is only needed with unpumped 1.60s using exhaust pressure.

I finally went over to the darkside late last year and bought YS's. The OS is good up thru about advanced, but the YS 1.70 has insane power that helps in Masters, and with todays very fat and draggy airplanes. The YS also spools up and down quicker. It also has a prodigious appetite for 30% heli fuel. I now budget more per month for fuel than I do gas for my car! Since I went to the 1.70, electric prices have gotten more reasonable, and frankly are probably cheaper to change to at this point. But stick with the OS 1.60 in lower classes as it is still the best bang for the buck out there.

RC11

My Feedback: (7)

Hi Jon,
I have been running your Cookbook set up for a couple of years now with Great Success. I hate using starters and if I have to use one somthing is not right. I have a new VF3 with OS160 and VP30 with ES pipe. It will not pull fuel to the motor untill I choke it ( finger in the venturi at open throttle) for maybe forty revolutions. My other 160 and 140 will get my finger wet in five or six rotations. After I get fuel to the motor it performs great. Any thoughts please?
Thanks much,
Rick Cilles RC11

wessco

My Feedback: (7)

Thank you very much for that file. now that gives me somthing to read tonight at work.

flywilly

My Feedback: (121)

Jon,
if you go electric does that mean you went over to the 'light' side?
Are you running the stock or CDI version of the YS? The reports indicate that the CDI is very fuel efficient (enough to offset the additional cost). I'm going to wait until OS produces the 200AX ... or at least keep wishing (well, I'd really like a 200RX, but I just don't see that happening []).
-Will B.
PS Thanks for your efforts in producing the 160 cookbook - VERY useful and a real time saver!!

jonlowe

My Feedback: (12)

Is the tank considerably lower than in the other airplanes? Are you using a different fuel filter that may be more restrictive? Are you sure the o-ring on the bottom of the carb is sealing properly?

jonlowe

My Feedback: (12)

I'm running the CDI version. Cut my fuel use by about 40%. But the cost per gallon of fuel is about $8 more, and the economy still isn't what the OS 1.60 had. Frankly, since a YS plus a CDI kit is about $950, the cost to go electric becomes more attractive.

Jon

Jeff Boyd 2

Like this Jon ?? . . and guess which prop !

I really like the 18.1 x 10W . . it flies slower with better throttle control. It also has slower downlines. I am running an Aeroslave pipe though . . so may be the difference.

Cheers, JB

Jeff Boyd 2

Personally, I don't run bearings with both seals fitted. Did that a couple of times and had short bearing life, even with a Stainless. I think the main bearing may run too hot without the cooling effect of the fuel/oil vapour flowing through it . . my opinion only.

I remove both seals on the main, and the leave the external seal in the front bearing (removing the seal facing in for lubrication).

PS. l also had a main bearing seal come loose sending "seal shavings" through the engine.

Cheers, JB

RC11

My Feedback: (7)

Jon,
You are exactly right!! Our new field has a slight grade in the pitts and I was trying to draw fuel uphill to start. I turned the plane around and pointed the nose downhill and VOILA!! it pulled fuel right to the carb! I will raise the tank a little and the problem will be solved! I love it when fixes are so simple!!!
Thanks Much,
Rick Cilles (RC11)

jonlowe

My Feedback: (12)

Yep, that's it. Just try the 17x12W. I think you will be pleasantly surprised. Much better pulling power and still good downlines. The engine likes the lighter weight also, and spools up and down faster.

Put the two pieces of your broken crank together, and you will see the sharp edge that has to be radiused.

Jon