tiffitech

No Motorboy, this isn't designed this way on this engine. The wrist pin is secured with simple lock rings made from spring wire here and the conrod has an
bore to provide some lubrication on the top. In my case this is clearly a bearing failure, parts of the wirst pin are "molten" and smeared around it.
(Thats why I wrote that I had to smooth the Pin somwhat)
We say in germany that this bearing has "gefressen". I'm don't able to translate this correctly then "eaten" may not be correct here.
As on many other engines the conrod/wristpin connection is designed to be the bearing. I know what you mean but have only seen this in my trusty
Mazda 626 115hp 2 litre engine, where the wrist pin is pressed into the conrod and rotates into the pistons. There are no lock rings as you described.

Kind Regards,

Holm

Motorboy

"Gefressen" can you use the word in english: seize or galling..

Same in Peugeot cars has connecting rod shrinked to wristpin (not pressed into) and the wrist pin is rotating free in the piston.

tiffitech

Ok, thanks Jens Erik. Maybe the wrist pins in the Mazda are shrinked in too, Don't know this, never dismounted this part in the past.

In the meantime I was in my garage and tested the R10RU with the modified carb. I had to shorten the spraybar again a little since it run still to fat at low end.
Now the carb is somewhat working, I got an reliable ide over minutes at 2100rpm with an somwhat heavy looking Taipan 11x7. Top speed was just above 10500.
The Transition from idle to WOT is "soso" not the very best, it sputters while reving up but I could set the carb that it dies when I make a fast transiotion to full throttle, so may be it needs some further tuning. I must say, that the engine bearings are not the best anymore, they where somewhat raw after the disassembling and cleaning of the engine. I think it will run better after some settle time. I've drawed around 500ml FAI Fuel trough the engine now.
I think I'll try to make some photos from the modified carb later today, also from the newer version where the LS Needle is going into the spray bar. This version actually works on an old MDS.40 Blackhead w/o any modifications. This is not he C2 carb like my MDS.38 has.

Regards,

Holm

BTW: Earl, your letter with the picture postcards just arrived here. Thanks again

earlwb

Thanks for the info, I had totally forgotten about screwing the mixture screw to the inside. That worked.
Yes you are correct, we can't drill the hole on the inside of the mixture screw any deeper, as it'll reach the groove for the O-ring seal.

blw

My Feedback: (3)

This is one of those things where everyone uses a slang term. Gefressen works pretty close to 'eaten up', or 'all ate up'.

tiffitech

Hmm, slang is good, but I simple don't know any other description than "gefressen" in german...
I think it is the official word for this.

Kind Regards,

Holm

tiffitech

Here are some pictures of different MDS versions and theyr carbs:



This is the oldest MDS40, it had a carb similar to the R10RU (Raduga) at bottom.
I've mounted an TN Carb from a Webra from Ebay, must have been a .60 size engine,
had to machine the shaft diameter down to 12mm on the lathe, works fine.
The engine has an unbushed conrod, same as the R10RU.




Next version, this is the Blackhead, his carb works fine if it has no airleak.
It has brass bushings in the conrod, had to replace that bushing on the low end.




Again, next version, still untested. Bought some Bits and a radio from Ebay UK, this engine
and the heavily glued ST G.34 (other Thread) where in the parcel too.




This should be the latest (C2) Version of the MDS Carbs, still unrun Engine got it from Ebay UK.





This is my 10ccm R10RU or Raduga or MDS.61 or whatever with his modified carb.

All engines are cleaned up with ultrasonics as you can see.

Sorry for the big pictures, buit I think thats better so, the server should be really faster than that from RC-Universe
and it has a fast connection to the net. I'm the admin ...

Regards,

Holm

earlwb

Sorry it took a long time to get the video clip uploaded and working.
Here is when I ran the 10cc engine using a 11x7 Master Airscrew Propeller. I forget if I was using FAI fuel or 5% nitromethane fuel at the time.
I was getting around 11,500 rpms for the engine speed that day. If I remember correctly my old baffled Fox 60 Eagle 1 was turning around the same RPMs using a 11x8 prop. The Fox Schnuerle engines were turning 11x7 and 11x8 props much faster still.
So I assume this engine likely has mild port timing, more in line with what you would want with a controline engine.
I think they simply took a controline engine and stuck a RC carb on it at the time.
So it ought to do better with larger props then.

[youtube]http://www.youtube.com/watch?v=XN0_adZ7u-8[/youtube]

tiffitech

??? what ...ooops?

Regards,

Holm

Edit: ...maked the images 30% smaller...


...hmm understand, ok.

Before I give a statement about the performance of this engine I would change the bearings on mine. I relally think they are not he best anymore.
The engine should make 1,103 Kilowatts +-10% (*grin*, 3 digits after the comma but +-10%). I've translated this to PS (wich is only very slightly
different to hp) and got 1,50 PS. The MDS 40 has a power Rating of 1,7PS so it is more powerful.
On the other side we say in germany "Displacement can't be replaced by something other than more Displacement" (Hubraum ist durch Nichts zu
ersetzten als durch noch mehr Hubraum). You should know this, since american's actually make the bigger engines

BTW: Somwhere above you wrote about only four hours lifetime of the engine, in the Manual ist stated "Motoresurs, Tschas 10" which should be translate to
Liftetime 10 hours if I got this correctly. ( As I already wrote somwhere here before I'm a east german from behind the iron curtain in the past. I had russian
language in the school (but never english) , but you forget a language that you never use in a relative short time. It's enough to read some technical manuals,
that's all)


Regards,

Holm

Motorboy

Measuring of effect is difficult to get exact from model engine manufacture. I recomment to measure effect if the propeller and rpm is known as here: http://www.hoppenbrouwer-home.nl/ika...rusthpv20d.htm

The standard engine size in USSR was 1,5, 2,5, 5, 10 ccm after the rules from DOSAAF (ДОС��Ф) ,and less used 0,8 ccm.

Correct, the lifespan at 10 hours fot the Raduga, but it is depending on enviroment, quality of fuel etc.. if you are careful, the engine will last longer..

earlwb

I can agree with the fact the larger the displacement the more torque and power you can get, even if a smaller engine develops as much or more horsepower.  A big prop is much more efficient, even if it is turning a lot less RPMs than the smaller engine with a smaller prop.
That is a good idea about the bearings. The Russian bearings would be questionable as to their quality.

earlwb

I was messing around with some engines to rig up a muffler system for a Fox Hawk 60 engine I had repaired recently, when I made a discovery.

On the MDS 10cc FI-RE engines. The port outlet and bolt pattern matches a FOX Eagle III and IV engine exhaust almost exactly. Not quite perfectly but really close enough to make it work without much effort. I found a couple of old metric computer case screws and bolted the old steel Fox tuned pipe header right up the MDS 10cc engine with no effort.
MVVS .60-.77 R or Fox 60R  (Fox 60 with cylinder rotated 90 degrees to make it a rear exhaust) have the same port size and bolt pattern.
Mac's Tuned pipe header adapter numbers 3720, 3721, and 3722 are the items to look for, if you need one.
http://www.macspro.com/headers_rear.asp
Of course the MVVS rear exhaust .60-.77 engine mufflers and pipe adapters would work too.

Now since rcmodelreviews.com found that the crankshaft is a weak link on these engines, you would probably want to use a muffler of some sort and not a tuned pipe, in order to reduce the risk that the crankshaft might break on you. The tuned pipe header and a Top Flight in cowl muffler can might be one way to do it. Maybe using a canister muffler off the end is another.



Tuned pipe adapter with Top Flight in cowl canister muffler.


One could mount a Fox muffler sideways too.

Kmot

My Feedback: (24)

I like mine with a tuned pipe.

[youtube]http://www.youtube.com/watch?v=iRwSP2K0n14[/youtube]

tiffitech

Yes, I know about the metric engine sizes since I live in a "metric" country

I forgot to attach this picture from the reworked carb of the R10RU, I've simply shortened the spray bar to allow the bush going over the the hole in the orifice.



Regards,

Holm

sarpet

this is original russian setup.

earlwb

s�rpet , That is an impressively short tuned pipe setup on the engine.
Do you know what prop, size and pitch they used on it?
What RPMs were they expecting it to turn?
Thanks

Kmot, I always loved your tuned pipe video. Scary stuff getting a .60 to turn lots of RPMs. What RPMs were you getting when you did it?
What prop did you use?

Kmot

My Feedback: (24)

Earl, I no longer remember what prop other than it was a Master Airscrew. According to my notes on the video the RPM was 17,510.

earlwb

That was most impressive. Thanks for the info.

earlwb

tiffitech,
How well did shortening the spray bar work out?
I was thinking that as the engine approaches full throttle, it tends to open the tip up all the way, and maybe that would be a problem with it running too rich or not.

I have a small mini-Lathe, but it is a Taig Lathe and it doesn't have thread cutting capability. So I need to make a fixture to hold a threading die and use it to cut the threads on the lathe. Of course then I have to determine if they even make a die in the thread size for the low speed mixture screw or not.
I had thought about machining up a small extension for the existing mixture screw too. but I am not sure it'll restrict the air flow more or not. Anywayit would be easy enough to solder it onto the end of the mixture screw.

tiffitech

Hi earl,

the shortened spray bar is working better in the carb as before, but I won't say that it is working very well. I have tho screw the LS needle almost full in, just before it seats to the end of the spray bar to get a reliable idle and this setting is very difficult. Full throttle isn't a problem since the HS needle is restricting the fuel flow to the amount you've set it, so you can lean it out properly here.
The problem is the midrange, from idle to full the mixture is first ok, than to lean, next to fat and then finally right again since the HS needle is working as you've set it.
The cause is the sluggish fit from the bore in the LS needle over the spray bar I think. Next where trying to change the deepness and the layout from the orifice to get it running right. I've closed the shortened bore of the spray bar with epoxy (easier to remove than solder) but that changed nothing on the behavior of the carb. It hesiates to rev up, sputters before going up.

I've changed the front bearing from the engine in the meantime and got the same raw rotation as before. The problem here was that the front bearing wasn't fully set down in the crankcase (same the original) so after you tightened the prob the bearings got tensioned axially.
I've sat down the bearing with my drill press, it's running free now but I don't get the RPMs at WOT over 10500 wit the taipan prop mentioned above (and can bee seen on the picture of the R10RU). I'll look if I have an APC prop somewhere..


I think the thread on the LS Needle is metric M3, nothing special in my country and I do have such thread dies. I'll check this for you later this day. You can repair the broken LS needle by simply grinding of the halve thats still in place and make a small new slit with a saw. The remaining thread length is sufficient to hold it in the carb.

It is totally unclear to me how someone is able to make an engine with tight fits all ower and is building a carb that can't be working at all because of sluggish fits and to short bushes for it, even when you know russian made mechanics for a long time. The fact that the design is one from OS don't make it clearer to me. They had simply to copy it properly.
They've rejected this design later and maked an LS neddle going into the spray bar. It seems to me as the proper way to get this working since nothing restricts the LS needle to go deeper in the spray bar as with the design we have on the R10RU. The parts are simpler to build, instead of this orifice you have to machine a cone to the LS needle for fuel metering but even then it is difficult to make a properly working carb I think.

I do have a non working, left over carb from one of the MDS .40 as you know, had replaced it with a Webra TN Carb.
I'll investigate how the spraybar is mounted in the casting of the carb body, maybe it can be changed?

...

I've spent the entire day yesterday to get an Snow-mill (?) from the neighbor working properly. Engine is ok but the plastic chocke shaft was broken in the carb, the drive belt was defective, and lots of other problems.. That's really a ****ty chinese machine. Problems all over the entire thing.

It snowed almost 50-60cm yesterday here.. some sort of panic-powder this is..


Regards,

Holm

earlwb

Thanks for the info.
The Chinese had the same problem for many years. they could manufacture engines that were pretty good, but they couldn't make a carb work.
Years ago, i remember all the carbs out of China were pretty much junk right out of the box. But it seems they have got it figured out nowadays as several cheapie no name generic engines have all worked quite well for me, with carbs that work too.

I plan on seeing if I can machine up something for a low speed mixture screw over the holidays. I might be able to cheat and drill and tap the body for a screw and screw in a small screw, and cut the head off and slot it. I'll think about it some more though. Nothing says it has to be a one piece unit. a little Locktite will keep it from coming loose too.

Konrad

True, I measure a Royal 40's needle holder and it had close to 5 times more clearance between the high speed needle and ID of the holder than that found on the OS 4B carb. The Royal "O" ring sealed this clearance just fine. Replacing the Royal needle holder with one that held the needle closer eliminated the false needling issue we had with the Royal (the needle holder of the OS 4B carb is a direct replacement).
See this thread about false needling:
http://www.rcuniverse.com/forum/m_10...m.htm#10015277

tiffitech

I've read the entire thread about the carbs some times before, but in this case the needle holder has nothing todo with the malfunction of the carb. This carb simply can't operate in it's original form. The geometrics of the Spraybar and the Low end Needle simplyaren't working at all.
This carb is broken by design.

@Earl: I'll check the thread in the carb today. Yesterday I've had to get my 5 years old son out of the kindergarden and had to drive him to the hospital. He had an accident with his nose to the head of a girl, so the entire day went other way as I've tought before.

Regards,

Holm

Edit:

Earl, the thread on the LS Needle is ordinary M3 as expected..

Regards,

Holm

Konrad

I agree, that the low speed mixture issue here is not related to the false needling phenomenon.

All the best,
Konrad

tiffitech

@earlwb:

If you still interested in modifications to the R10RU carb, I have some news for you.

Above is a picture from an MDS40 blackhead carb, I've disassembled this carb now and made pictures from the Low end Needles,
also a picture from the LS Neddle from the not working .40 Size carb that I've changed against the Webra TN Carb.





Sorry for the unsharp pcitures, I don't have the best cam.. (you can see that the thread of one needle is shorter than
that from the others, I think you already know why..)

The Carb from the Blackhead is working good and that bush at the end was replaced by a cone, lengt 3,5mm,
diameter at the thread side 2mm and at the front 1,55mm. They used the same tubing for the spray bar in all versions
but in the case with the cone without the orifice and the hole. The spray bar is simply cut rectangular and ends in the
middle of the air hole of the barrel. I think that needle is even easier to make than that bushed variant.
The Needles from the .40 size engines are identically to the .60 size. You have to close the hole in the spray bar with solder
if you try to modify it like this..

Kind Regards,

Holm