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Straight Talk on the PAW .60 TBR R/C Diesel

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Straight Talk on the PAW .60 TBR R/C Diesel

Old 02-06-2003, 05:30 AM
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R/C Phile
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Default Straight Talk on the PAW .60 TBR R/C Diesel

I am writing this post because a year ago, I wanted to buy a 40-60 size diesel engine and found very little info about how they really perform and fly. The idea was to try something different and the one I picked is the PAW .60 TBR R/C.

Apparently, it is so different that I was unable to anybody to tell me in any details what I could expect out of this beast on an R/C plane!

There are plenty of Web sites that go into great length on how to start a Diesel, run it, care for it etc. There are a few that talk about flying diesels on "old timers" parasol wing type planes and a few on C/L Combat planes but not one web site talks about flying a PAW .60 diesel on a "regular" R/C plane.

I will not get into starting and caring for as you can find that else where. I will give you the "Skinny" on how it runs, performs, and flys.

Also, I will attempt to dispel the Diesel stories and Hear-say so here it is:

Things That I found NOT to be True:

1)Miraculous power compared to Glow: In my experience a good .46 glow has more usable power than this .60 Diesel. The rated horsepower for the PAW .60 TBR is 1.2 @ 11,000 RPM but no matter how small the prop (Within the recommended sizes) I never got mine to break 8800-8900 RPM. Since horsepower is a factor of Torque * RPM I am fairly certain that the actual usable HP output closer to or below 1.0 HP (As supported by the prop HP figures on my bench tests which were closer to .6 - .8 HP as calculated by ThrustHP) .

In the Glow camp An OS .46 FX is rated 1.6 at 16,000 and heck the OS .32 SXH in my heli is also rated 1.2 hp at 16,000 and those RPM figures are easily achieved by those engines . My OS 32 SXH Tached 14,000 RPM on the bench with a 10 X 6 prop which would yield 5.8 lbs of thrust and 1.17 HP according to ThrustHP. The Diesel power gain over Glow may have been true 25 years ago but I don't think it is the case any longer.

2)Incredible Thrust: Although it will swing large props it does so at such low RPM that the incredible thrust claimed by some is simply not there. Even with large props significant thrust is generated by significant RPM. In my experience with testing several props 4 to 7 lbs of thrust is about all I get out of this engine. Again most 46 glows can do more than that fairly easily. To illustrate this point I can tell you that I had it mounted to a small Lanier Stinger .40 which weighs about 6.5 to 7 lbs total flying weight and vertical performance was not it’s forte. If you tried to climb straight up it would not do so for very long.

3)Fuel Draw so great there is no need for muffler pressure. This had not been my experience, if you point the nose of the plane up it does lean out and lose power without muffler pressure. With muffler pressure it is fine and it runs consistently at any attitude.

4)Difficult to run / start. If you follow instructions it starts easily and it’s not rocket science to adjust properly. However, every time you start it you do have to increase the compression and decrease it once it is started. It is not “set it and forget it” and it is a bit more “fiddly” than a glow in my opinion.

5)Unreliable Idle. If adjusted properly, it will idle fine and for several minutes then accelerates normally without any problems.



Things I found to be True:

1)Lightweight: It weighs in at approx 17 ounces including the muffler which is actually a bit lighter than an OS 46 FX with muffler

2)Low Noise: It does sound mellow and it is very quiet. In flight you hear the rush of the air over the prop and airframe as much as you hear the exhaust. Short of glider or an electric this is the mellowest sounding (and flying) airplane at the field.

3)Runs Cool: It does indeed run very cool. You can actually touch the cylinder while it’s running and not burn yourself, I am told and believe it would work great within a tight cowl with few openings.

4)Starts Easily: Once you get the hang of it, the electric starter is not necessary. It typically starts with one or two flips.

5)Incredible fuel Economy. Very much so, mine will run over 30 minutes on 10 ounces of fuel.

6)Slow Throttle Response: Even with all settings optimized, Throttle response is consistent but slow. The engine accelerates as if it had a heavy flywheel, even when running a relatively light 12 inches prop

7)It smells bad: The exhaust smell is actually kind of neat, as it smells like a Kerosene lamp but the raw fuel itself is incredibly smelly and nasty stuff, the fumes are hazardous to your health, and it must be handled very carefully. Also, the exhaust residue has a very persistent smell. For me the stories about how the smell is an acquired taste boil down to this: You might “sorta” get used to the smell but it sticks to you, fouls your clothes, and everybody around you smells it until you thoroughly wash-up and change your clothes. With glow fuel you just wash your hands and the smell is gone. My wife can always tell if I have been messing with the Diesel.

8)Messy: VERY MESSY! The residue on the plane that is very thick, dark, it kills grass, and it ruins clothes. It is fairly easy to wipe off the airplane but very difficult to remove from clothing. This is exacerbated by the fact that the engine leaks the stuff like a sieve. It leaks oil from the front bearing, muffler, and compression screw. The factory acknowledges the leaks but refuses to address the issue.

9)The PAW carburetor is a bit crude. Some may disagree with me but I tend to agree. The carb does lack an idle needle / airscrew adjustment and with only one needle for it all it is a compromise. The best idle mixture is slightly different than the best top-end mixture if you try to max out the top RPM the Idle will suffer slightly. I think that an engine of this quality and price should have two needles.


Engine Performance Tests: I was warned that this is no speed demon and boy, were they right. If you are looking for thrilling vertical performance and speed this ain't it! Here are some figures on props that I tried: (Static Thrust and Speed Calc'd with ThrustHP)

Prop RPM Thrust (LBS) Speed (MPH)
15 X 6 Master Airscrew 7200 7.6 41
14 X 8 Master Airscrew 7600 5.95 56
13 X 8 APC 7900 5.3 59
12 X 10 Zinger Wood 8200 4.1 77
12 X 6 APC 8800 4.8 50


Flight performance:

My Idea was to use a small and light .40 size plane (Lanier Stinger .40) to get great vertical but it turned out that the wing loading is a bit on the high side with this engine. Any hopes for real performance on this plane / engine combo requires too much speed for this engine.

It was Practically Un-flyable with the 15 X 6 and the 14 X 8 as it was too slow. The 13 X 8 had decent vertical
once it was going but was reluctant to leave the ground! The 12 X 10 seemed most agreeable overall. Why so much Pitch? Not much RPM'S and I was trying to make up for it by using the torque.

Once I got a decent prop selection it flew fine for general flying around and mild aerobatics not requiring too much vertical performance. It does gets a lot of attention at the field from the compression screw (What is THAT?) the quiet mellow sound, and the 30 minutes flights.

When you test a diesel make sure you are wearing old clothes. If the exhaust oil gets on them (and it will) it ruins the fabric with nasty stains and a terrible smell.

Do I actually like this engine? Oddly enough I do. It does look great and you can tell it's built by craftsmen and not robots. It really is beautifully made with evidence of very nice "Hand Made" machine work (Although Simple, the machined Carb does Look beautiful) . I like the way it sounds and the general handling is fine once you figure out the Prop / Mixture / Compression equation.

Also, I thought that the US 180.00 plus shipping from Carlson Imports was a reasonable price for a hand-made .60

I am planning on putting it in a biplane that weighs about the same as the Stinger but has twice the wing. Also, I will custom adapt the plane with an integrated and very long exhaust extension inside the fuselage that exits near the rudder (Back pressure is a non-issue on this thing) and a sealed cowling with strategically placed vents to allow just enough cooling while catching the gunk and not mess-up the plane's finish and my clothes.

That plane should fly fine at low speed, take care of the wing loading issues, and deal with the nasty exhaust oil. If that works according to plan that will be a great mellow plane to relax and calm me down from my Heli 3D attempts!

This post was long winded but I think it will help you guys that are interested in something different in a (Relatively) large R/C Diesel with a British accent!

Regards.
Old 02-06-2003, 01:08 PM
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dennis
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Default Straight Talk on the PAW .60 TBR R/C Diesel

The PAW 60 engine has been often described as a big friendly LUMP. That you would even presume to expect this motor to be able to supply the ponies to maintain unlimited vertical is also unrealistic. It simply wansn't designed for it. It is a 'niche' motor' which means that it has a specific function of mainly being used in large slow flying planes,example large trainers, old timer free flight conversions.
PAW motors have been in business since the 50's as such the design of the 60 is really 50 year old technology,including the carb design which if you look at it has a choke area more to a 19 sized glow. And yes your right the carb design is simplistic and coupled with a diesel running upright it is not tjhe best at handling the puddling that accumulates in the crankcase with prolonged idling. Incidentally the best positions to run a diesel are sideways and inverted.
Heres a link to have a read on more modern equipment. I'm not really trying to bash the PAW motor it is what it is and certainly there are considerably better examples available.
To solve your other complaints, the diesel is pretty impervious to backpressure so run a hose from the exhaust to the tail of the plane and waste the exhaust oil past the tail. To kill the smell of the fuel use candle scent, your choice, and please only a few drops are necessary otherwise you'll compromise the fuel.
Clothes and their stains require a soak in a degreaser, but your right it is tough on clothes so I always have certain stuff just for diesel days.
Go to www.airbornemedia.com/davis/ and do some updating on your knowledge of diesels.
Remember if the motor both glow or diesel isn't designed as a performance motor then you are simply beating it to death to expect it to deliver more then it was designed for. In glow an example would be the OS/LA series of motors, simply not designed to do more the be a good basic motor.
Old 02-06-2003, 02:26 PM
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Hobbsy
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Default PAW .60

Mine is going on a Byron's Sundowner, and I have no illusions about even trying to go verticle with it. My PAW .19 and the .60 do not leak a drop from the front bearing but the .40 does a little.
Old 02-10-2015, 02:41 AM
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Thanks for this great review !


Diesel enthusiast rc pilot.
Old 02-10-2015, 10:05 AM
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Yes I think that the PAW .60 was more for slow flying planes, trainers, old time models, free flight and such. It has a small intake that limits performance, but a small intake has a stronger fuel draw too. Keeping the power down also helps it to be more quiet too. Slower propeller speeds reduces noise as well. Also it should have really good fuel consumption rates and be something of a miser for consuming fuel. So it won't be a high performance engine. But it should be easy to start and run though. That may make a lot of people, especially beginners happy. I think the PAWs should probably be better compared to the old vintage spark ignition engines made up until the 1950's.

The higher performance diesels were likely the ones that MVVS made. MVVS has made large displacement diesels and those should develop much more power. But more power means more fuel consumption. The high performance diesels tend to consume fuel at higher rates, more like glow engines. They also make more noise and turn props faster that make more noise too.

Davis Diesel Development offers some diesel heads for converting engines. DDD has made heads for many engines over the years too. So usually one can see a DDD head pop up for sale here or there for different engines.
Old 02-10-2015, 02:53 PM
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I had a PAW .60 for years powering a COSMO KING .40 SR 'utility' R/C ship.

I agree with R/C Phile's well thought out comments.

For fuel smell issues, make your own, and try substituting white spirit (U.S. mineral spirit) as the base instead of lamp oil or kerosene. It burns cleaner and with much less of that 'diesel' odour.

My Merco .61 ABC Diesel (loop scavenged) puts out similar power to the PAW .60.

Now ...

if you want a .60 size diesel with more power than a modern glow .46, try the MVVS .61 diesel. Still available at time of posting:

http://www.mvvs.cz/diesel_engines.html

Takes a little setting-up, and experimentation with carbs and props to suit your application, but MUCH more power is available; as one would expect from an engine featuring a 'modern' Schnurle port / ABC set-up.

Last edited by fiery; 02-10-2015 at 04:46 PM.
Old 02-10-2015, 03:20 PM
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This thread should have stayed dead since it was 2003 but alas here it is. I moved it from Glow to Diesel. To add to what Derek said several of the glow to Diesel .61 conversions will stomp the Paw .60. It does get credit for stone reliability, easy starting and in my opinion is pretty smooth running. The Fox Eagle .60 has nearly the same bore and stroke as the MVVS and MOKI .61 long stroke.

Fox Eagle .60
Bore====.907 or 23.04mm
Stroke===.937 or 23.80mm for .605 cu inch.

Last edited by Hobbsy; 02-11-2015 at 06:35 AM.
Old 02-10-2015, 07:54 PM
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Originally Posted by Hobbsy View Post
It does get credit for stone reliability, easy starting and in my opinion is pretty smooth running.
And gets credit for being still in production!
Old 02-11-2015, 02:30 AM
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I would be happy for comments about Enya diesel engines if someone has experience in them. A few months ago I bought Enya ss 30 BB diesel. I have not run that yet but Enya informs power 0.9 hp. The same power as it's glow counterpart. Enya's fourstroke diesel does not seem to be so efficient 0.6 hp from 5.9 cc displacement.
Old 02-11-2015, 06:33 AM
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Here is my Enya .25 Diesel turning a Graupner 12x5.

Also my Saito .80 on Davis ABC mix turning a Bolly 13.5x8, the early Saito .80 had a 15.5 to 1 compression ratio. No bad, I say
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Old 02-11-2015, 07:59 AM
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On Youtube one can find a couple of smooth running Enya diesels. Nice pics, Black Saito sure looks convincing.
Old 02-11-2015, 12:03 PM
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Irvine .40 Diesels are great engines if you can locate one. Of course the LA .46 conversion will run with the best of the .50 sized Diesels.
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Last edited by Hobbsy; 02-11-2015 at 12:10 PM.
Old 02-11-2015, 05:50 PM
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Originally Posted by macmac View Post
I would be happy for comments about Enya diesel engines if someone has experience in them. A few months ago I bought Enya ss 30 BB diesel. I have not run that yet but Enya informs power 0.9 hp. The same power as it's glow counterpart. Enya's fourstroke diesel does not seem to be so efficient 0.6 hp from 5.9 cc displacement.
I have the SS25DBB Al-Chro, and the SS30DBB. I've done a lot of flying with the 25, and a very small amount with the 30. Both are beautifully built, with excellent fits. I find that compared with most of my other diesels, the Enyas are trickier to get a really good setting with (mine are CL versions). They seem to unload quite a lot in the air, so what seems like a good setting before launch will generally result in misfiring once up to speed. Consequently I have to launch with more compression than I'd normally like, in addition to the usual slightly-rich mixture.

Enya's power claims are normally accurate or even conservative, but I'm not sure how they come by their figures for their diesels. I simply can't see how you'd ever get the claimed power from them. To get near an engine's claimed hp, you'd normally have to put on a smallish prop and spin it at high rpm, but that doesn't work with the SS25D or SS30D - they simply don't seem to want to turn high rpm (although it's been a while since I experimented with this). A 10x6, for example, which is on the smaller side for these engines, would need to be turning at about 13000 to be in the region of .85 bhp - which is never going to happen. Hobbsy's .25 spinning a 12x5 at 8760 (a pretty creditable result, and plenty of real-world thrust for a .25) is managing a bit over .5 bhp. I just don't see how you'd get near .85-.90, but then again, I'm not too bothered, since the way they run is fine for my purposes. If anyone's found otherwise, I'd be really interested to hear about it. They're still lovely engines and well worth having.

Steve
Old 02-12-2015, 02:54 AM
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Originally Posted by steve111 View Post
Consequently I have to launch with more compression than I'd normally like, in addition to the usual slightly-rich mixture.

(
Thanks for this info Steve. I use diesel engines in trainers and vintage models so running on rich mixture doesn't bother. I like to run engines with a bit rich mixture. I also reduce compression as far as it does not reduce rpm too much. That is for elongating engines lifetime or parts replacement cycle.
Just wondering if you let engine heat up enough before final adjustment and takeoff ?

Mac

Last edited by macmac; 02-12-2015 at 02:58 AM.
Old 02-12-2015, 04:35 AM
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Originally Posted by macmac View Post
Just wondering if you let engine heat up enough before final adjustment and takeoff ?
Yes, I do.
Old 02-12-2015, 01:12 PM
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Over cooling in the air perhaps Steve?

Maybe slip a couple of 'O' rings over the fins to hold the heat in may work?
Old 02-14-2015, 10:41 AM
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I was wondering if heat could be the issue (actually the lack of) or if perhaps the Enya's finickiness being due in part to them taking what seems like forever to break-in? I have a glow SS30bb that gained close to 2000rpm from the bench break-in to about 2.5 gallons of fuel. It wasn't all that finicky beforehand, but it's performance was far from stellar initially. It's the iron/steel model.
Old 02-14-2015, 02:27 PM
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I've found all their Schnuerle diesels (CX11, SS25, SS30) to be similar when it comes to getting a good setting. My CX11 and SS25 are AAC (and a friend's CX11 Ultra is ABC), so I doubt that it's break-in related.
Old 05-26-2015, 09:38 AM
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https://www.youtube.com/watch?v=QkCVRpx_qyQ

Here is my video on running a PAW engine. Skip to 17:00 if you just want to see it go. This vid is of a .40 but I assume the .60 runs similarly.

Cheers,


Bill
Old 05-26-2015, 06:48 PM
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Wow! Wonderful idle with the 40!
Old 05-27-2015, 03:02 AM
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Very informative video, good job Bill.
Old 05-27-2015, 03:46 PM
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Thanks guys.

I enjoyed that day with the PAW and have good memories of running not just that engine but others too. I don't run diesels as often as some and I'm sure there are experts here that will have something to add or possibly corrections.

Maybe I need a PAW .60.?.?

Cheers,

Bill
Old 05-27-2015, 07:39 PM
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Any idea what a new con rod for a PAW 60 would cost? I picked up an engine on the big auction site, and it has a major rod knock.
Old 05-27-2015, 08:29 PM
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PAW 60 conrod would be 22 pounds (according to the web site.)
Old 05-28-2015, 03:15 AM
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I picked up an engine on the big auction site, and it has a major rod knock.
What do you mean by rod knock? PAW's are really stout engines built from the drawing boards as a diesels. It would take some abuse to hurt one. I suppose anything is possible though.

Bill

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