DaveyMo

Well after monitoring a diesel engine over on the Swift Engines auction over the past two years, I could no longer resist and took the plunge. I'll soon take delivery on a 2.5 cc KMD (Russian) diesel engine (item #736 on the Swift site). Any advice from the collective wisdom (such as it is!) on this forum about the engine would be appreciated.

This is my first diesel engine, and I know only what I've read about diesels on this forum. To start the discussion and to provide you some options that I might want to consider, I offer the following:

1) You've got more money than sense - that mill's a real loser! Ditch it ASAP and get a PAW!
2) What a beautiful example of Russian technology. Keep it in pristine condition for a museum display only.
3) Learn how to break in and run this engine. It should make for good control line power.

As you might surmise, I'm leaning (hoping) towards Option #3 though I'll keep an open mind. No comments will be rejected by this newby!

Thanks.

Dave...

paw080

Hi Dave, Choose option # 3, then fly until it breaks. You'll have gained enough

diesel know how to select from the many suitable diesel engines available for

control line flying. Good, strong .15 cu" diesel engines can and do fly full size

Flite streaks very well on 60' lines. Be sure and use a good fuel formula for

your engine...NOT 1/3, 1/3 1/3 castor, kerosene and ether!

Tony

AMB

DaveyMo they can be a bit of a lottery lets hope you get a good one, also if just starting in diesel land buy a premix fuel Tower Hobbies has the Davis fuel 12.95 qt do not mess around mixing fuel till you get a handle on diesel setup and run
when all is well its just fuel-flip-start you can also get a tt40 from tower , get a davis head he just did a re run on them makes a awsome diesel conversion, hopefully Fox will be back in production on the 15 ( they maybe now)
they do a lot of government contract work so the model engines go on the back burner again Davis head for same great engine martin

Recycled Flyer

Check out Maris Dislers KMD review on ACLN issue 81.

Seems to really like to rev and 22,000 rpm seems to be its peak horse power spot.

Warren B

Hi Dave,
I have both the KMD's the earlier black head and the later "white" head.

The black head is reputed to be better, but both mine run very strongly.

I would have to say the KMD is not necessarily the easiest choice as a first diesel (a PAW would be much easier).
The KMD's are not particularly vicious, but they do start suddenly and run hard.
The lack of a conventional bar type compression screw also adds to the general fumbling.

For my own convenience I drilled through the square on top of the black one's compression screw and pressed in a bar adjuster, the screw is soft so t's easy enough in a drill press.

Try and 8x4 prop as a starting point, they do like to rev.
And whatever you do, don't be tempted to use an electric starter.

If you are worried about bitten finger, I can suggest my standard accessory.
It's a small piece of carpet wrapped around your flicking finger with the pile facing inward.
Trim to length so the ends only just meet and it's a good firm fit on your finger.
Then wrap multiple layers of masking tape around the outside.

This work really well and lasts for ages.
Far less clumsy then a chicken stick, and doesn't get slippery like the old rubber finger protectors.
And no pain when then engine gets a bit snappy.

fiery

My Feedback: (2)

This is what my "St. Petersburg" build black cylinder version looks like, for those who may not have come across the KMD 2.5 cc. Reputedly finished to a higher standard than the later "Moscow" plain cylinder version.

Mine is a superbly set up example, silky. Starts like an Oliver. Fine performance.

http://www.youtube.com/watch?v=4gqw70icL6Q

DaveyMo

Wow, but you gents have really come through! Many thanks for taking the time to help this newby. Now for some comments, in reverse order:

fiery: Such a great set of photo's of a pretty mill there! I take it the black wheel thingy is for the compression screw? Do you find it necessary to use that lock nut on the compression screw, or isn't vibration a problem? Nice bench running setup you have there.

Warren B: I'll certainly take your idea of any adjuster bar under advisement. It shouldn't vibrate out if I can get a tight fit, eh? Yours is the first I've ever heard of using carpet for finger protection. What a nifty idea! I'll salvage some from a chunk on hand and do just that. I'm also trying to interest some youngsters in C/L flying, and this should help their confidence level with engine starts.

Recycled Flyer: I took a peek at the ACLN article. I intend to do a tear down for an internal inspection before firing up the KMD, so the contra-piston mod technique might come in handy. In fact, the whole series of ACLN articles is quite the resource. Much obliged for the tip.

Martin: Yup I gather that this engine is somewhat of a gamble, but not only am I cheap but I like to tinker. The information in the ACLN article might increase my odds of getting this thing to run well. And yes, I'll run only a Davis pre-mix from Tower. Thanks for the tip.

Tony: What luck! I happen to have hard copy plans of the full-sized Flite Streak that I'd intended for another engine. If weights are comparable, perhaps it'll serve a dual power use. And 60' lines will be sweet.

Much obliged, all.

Dave...

brokenenglish

Dave, one important point that hasn't been mentioned.
As stated, don't use a starter,
BUT, begin by getting a propeller that you can reasonably flick!
Wood or "Graupner Grey" props are good.
The really sharp carbon fiber props, such as the Master Airscrew carbon props, are painful (if not dangerous) to flick and, if your engine doesn't start reasonably quickly, you'll soon be losing blood!
IMO such propellers just weren't designed to be hand started on diesels.

AMB

good point I use mainly wood zingers bump on finger yes gash no if kickback ! do not fly competition so I do not require that extra 500 rpm thrust is what flys the plane martin

maxtenet

Haven't you guys heard of leather work gloves? You can get 'em pretty cheap anywhere. Home depot, Harbor freight! Light and easy to use. After many years of bleeding fingers I have settled on these as the best option. You can feel the compression and they prevent cuts.
Max

brokenenglish

Sorry, I expressed myself badly...
If you have a good diesel starting technique and avoid sharp propellers, you won't have any problems with cut fingers, or need gloves or similar.
But the gentleman who made the initial post started by say that he is a "diesel beginner".
It's therefore not unlikely that he may get into an overcompressed/flooded situation that we all know...
In such a situation, if he's just using any (sharp) propeller, manufactured on the assumption that everyone uses a starter, then he has a problem.
For me, the best solution is to choose an appropriate propeller, but it's true that gloves, etc. could be used, although I never have in 60-odd years.
I can't remember the last time I cut myself flicking a diesel, but it was a long time ago...

DaveyMo

Good discussion because some good points came out of it, maxtenet and brokenenglish. My plan is to hand start with an 8x4 wooden prop with some type of protection on hand (glove or the carpet gizmo suggested by Warren B). Thanks!

Dave...

Warren B

The choice of finger protection, glove, chicken stick, finger stall or none is personal preference.

For most of my engines I choose none - a fast flick keeps me out of trouble (you need to flick a diesel much faster than a glow - takes a bit of practise).

However for a few high performance engines using small/light props the occasional whack is hard to avoid.

I've found the leather glove slow to put on/remove and although it stops most cuts, the occasional whack still hurts.
Chicken stick is far too clumsy, you lose most of the "feel" and deliver a slower flick.
Rubber finger stall is too slippery.

My carpet one doesn't get slippery, fits your finger perfectly and you can still get to the needle or comp screw quickly.

Anyway as I say a matter of personal preference.

Here are a couple I prepared earlier.
The hot melt seam holds the carpet ends together to make wrapping the masking tape easier, but it's not essential.

fiery

My Feedback: (2)

A rubber 'purpose made' finger protector costs just a couple of dollars, and every cut on it is a whack or cut I did not receive.

Best investment ever if you like to hand start engines. I replace mine about once every year or two as they get cut up.

They are getting a little hard to find now. Owen Engines stock a good one packaged by MP Jet.

DaveyMo

Easy to make and functional, Warren. Thanks for the tip and the photo's.

gcb

Here is a pic of both types of KMD.



I would use a 9x4 to 9x6 prop for the first runs. This will give more flywheel action until you get used to starting it. Make sure you hand start it on a bench at first. Learn to flip-start with prime only (no tank). When you can reliably start on a prime, add the tank. Once you get it running on a tank, run it rich for about a minute to get any residual junk out, then lean out the needle and LOWER the compression a bit to see that you are not running it over compressed. I like to always peak it by starting from a lower compression setting. Run it for about a minute at peak then pull the fuel line and let it stop and cool. Once it is cool, reconnect the fuel line and run it at peak again for about a minute then pull the line and let it stop and cool. Running it up to temp plus the cooling is called heat-cycling. A dozen or so heat cycles should render it broken-in enough to put on a plane. You can now switch to a smaller prop without as many bloody fingers as some of us endured.

For lots of diesel info check out the Canadian diesel combat site (http://www3.bc.sympatico.ca/dieselco...ut_diesels.htm) Adrian Duncan provides a lot of explanation and info about the care and feeding of diesels.

Good luck and welcome to diesels.

George

brokenenglish

I agree with George. I didn't want to raise disagreement about initial prop size, but your 8x4 option represents just about a minimum "high performance" prop for this engine.
Particularly if you're a "beginner", you don't want a "max performance" prop, you need something that is easier and less vicious to start.
I agree entirely with George's opinion.

Warren B

Yes, thinking again I also agree, a heavy 9x4 or 9x6 would be a better choice for a new tight engine and a first time diesel user.
Both my KMD's were already used so I naturally went straight to a moderately fast prop.

In fact the 8x4 still spins well under peaking speed for the KMD, need to drop to maybe a 7x5 or 7x6 to start to see it go properly (mine still seems quite happy on a 7x4 on the bench, but might over-rev in the air).

DaveyMo

Many thanks again to gcb, brokenenglish, and Warren B. I truly appreciate how you all arrived at a consensus opinion on the best break-in prop size (9x6) through the use of reasoned discussion. This site and you gents are the best!

Thank-you, George, for providing step-by-step guidance on engine break-in. When I first read it, it seemed arcane until I read through the link to Mr. Duncan's rationale on the importance of heat cycling. I'll follow your (and his) directions to a "T" when the time comes to bench running the KMD.

Speaking of a bench run, the possibility of doing that in the near future seems remote. I'd like to give you a progress report, but we are immersed in a long spell of cold weather here in Wisconsin. At any rate, I'll post a shot of the engine when it arrives if nothing else.

Lots of fun! Thanks again.

Dave...

DaveyMo

Well, the KMD finally arrived. A very nice looking mill as you can see (not sure how the photo ended up in the middle of this sentence). As usual, I've got a few questions.

It looks brand new, and a note with it stated it's not been broken in. Can't turn the crank over at all, so will need some kind of loosening (heat, penetrating oil, solvent, etc.). I recall reading somewhere that a few later versions of this engine came off the line with machining residue in the crankcase. I've no problem with disassembly if needed.

Can anyone hazard a guess as to the purpose of that little red dot and the structure it seals (adjacent to the contra piston screw)?

Thanks!

Dave...

123Cat

A high pressure blow out button ,


In case maximum cylinder pressure is exceeded

Edit , Its not that ,

Something like the maximium amount you can turn around the comp screw tommy bar before you over compress it

DaveyMo

Ah, like a safety valve on a pressure cooker. Thanks. Do you know if this is unique to KMD, or if other producers do the same?

ffkiwi

Not exactly-though a few other producers vent the head-the Barbini series being a case in point. It is not unheard of (depending on contra fit) for pressure (and fuel residue) to bleed around the contra during use-and pressure build up in the head whilst running-which often manifests itself in the comp screw unscrewing and backing off-a vent hole in the head prevents such pressure build up. [these vent holes are small though-perhaps 1/32" in diameter]
Another explanation for your 'red spot' in the KMD is that it may be a means of introducing friction to the comp screw by some form of gland packing forced down a channel which intersects with the comp screw thead, and is subsequently sealed off at the top to prevent the stuff backing out. If you're familiar with water valves and model steam engines the concept of 'gland packing' is quite common....
.....giving some more thought to it-it's hard to tell from the photo whether it is red paint in a slight depression on the head-or something filling up a vertical hole. Another niggle reminds me that once upon a time, the KMD had a thumbscrew type comp adjustment-and a small vertical wire pin provided ratchet action on the serrated outer rim to hold the setting. Your photo shows what appears to be a small diameter vertical hole (possibly 2) in between the comp screw thread and the red mark. Equally-they could simply be minor blow holes in the head casting-which looks pretty rough....

ChrisM
'ffkiwi'

123Cat

After reading your answer ffkiwi could it be urethane poured into that hole to give friction to the comp screw

ffkiwi

Yes-quite possibly....or something along those lines. We know that these KMDs were widely produced, and as with other mass produced Russian engines there seems to be quite a bit of minor detail variation from batch to batch and/or manufacturer.......it would appear from this and other Russian engines, that they were produced in more than one location-and that casting quality and fidelity as well as finishing techniques varied quite a bit.....

ChrisM
'ffkiwi'