AndyW

My Feedback: (1)

I was the grateful recipient of a Cox TD heavy duty crankshaft a few weeks ago. Thanks Stewart. A beautifully made piece that needed a home right away. As the crank diameter was just a smidgen larger than the Brodak/CS crank, that's where it went. I had some good luck taking this neat little engine to its full potential, topping out at 19.9K on a 6 x 3 Tornado prop. On a 5.7 x 3 APC run recently, that one topped out at 24K. Ouch, sounded like a loud TD .010, and that's WITH the muffler.

I'm into diesel conversions in a heavy way and this engine got the chance to run on stinky fuel,,,, on the bench. I broke two, stock cranks in the process.

So it wasn't long before a Norvel crank was installed but for some reason that one didn't run well at all.

Well, I wasn't expecting much in light of that but here, http://www.youtube.com/watch?v=ykRzLyzvaM4 it looks like we have another winner. Since this was taken a few days ago, some tweaking and extra break-in delivered the anticipated 19.9K on the 6 x 3 Tornado prop and 25% Cool Power. At first, the throttle didn't idle as low as I'd been accustomed to and acceleration was a little ragged. But I had that problem with the first engine and this gave me a chance to try and solve the issue. Some rework of the throttle produced a reliable 5K with instant acceleration. It's been flown on the Low Stik and now I can do very low and slow aerobatics more confidently. I am very pleased with the outcome of this project to say the least.

Pictured is the crank along with some mods for more power. But for some reason, the mods didn't deliver more than a few hundred extra RPM, well within the range of variability. BUT, the engine now seems to run more smoothly at low RPMs.

In any case, this one will get the diesel treatment in due course. I'm really hoping that the crank will hold up. I've been getting inquiries from the UK about a light weight, low cost 1/2A diesel for controline use. A standard Medallion crank will be installed into a stock case. Both have round intake ports, more in line with the original concept. It just may be that the lower fuel demand of diesel makes the larger, rectangular intake port unnecessary. CS offered this neat little engine as a diesel and I did get one but their contra-piston design, while unique and innovative had issues.

If the Medallion crank delivers the goods without breaking I'll modify the ports to a rectangular shape but the crank won't be cut as long as you see in a stock TD. I've modified Medallion cranks to look more like a Norvel, with round corners and got the same performance as a stock, TD crank. The elimination of stress risers may get us what we need. Pictured is the Brodak/CS crank, the Medallion, a TD, modified Medallion and a Norvel Crank.

The other neat thing to try here is to get some TD left hand cranks and see if we can get a matched pair for twins with counter-rotating props. I've done this with the VA MK1 and at first, it looked like a go but the only left hand prop available is a Tornado 6 x 3 and the VA doesn't do well with such large lumber. Best I've found for the Mark 1 was the APC 5 x 2. At 22K plus, this prop delivered better power than a 6 x 3 Tornado at 16K. At that RPM, my twin was a slouch. I never had a flame out on either engine but it just wasn't a lot of fun staggering around in the air. If I can get a pair of twins doing 19K on the Tornado, and get reliable throttling, I'll be a happier camper for sure.

ffkiwi

Nice work Andy-what was the origin of the heavy duty TD 049 crank? My experience with TDs (30+ years of it) is that standard TD cranks are fairly good-and the weak point is the ball and socket little end on one hand and the plastic intake assembly on the other. Your figures for the CS are right up there with what I'd expect from a good TD and that % fuel

ChrisM
'ffkiwi'

AndyW

My Feedback: (1)

Thanks Chris,

One denizen of your big neighbor to the west, Stewart Clydsdale, provided me with one to play with. If you enter, 260387051369 on that B*y thing, you'll find the crank described as, "Cox Tee Dee RC 05 Killer Strong crank shaft" I had an RC .05 and it had a standard, TD crank. But LiteMachines had special TDs made up for their heli and I believe that this is the way the crank was made for them. I'm not certain about that so don't quote me.

In any case, it looks to me, like a crank should look. Maximum counterweight and it even has a hollow crankpin. Something you only get on SOME larger engines. This has me concerned a bit with diesel but I've never just broken a pin on a Cox crank. The entire web broke off with the break starting at the sharp corner in the port. This was on an engine that was run extensively trying to perfect good throttling. That engine was run up and down, by cracking the throttle open by hand, many many dozens of times. As you might imagine, the sudden acceleration would give that shaft a good twist every time. Eventually it gave out. This has never happened under normal operation, though.

The next two I do using the killer crank will not feature the cut outs in the crank web. In this case they did little and only served to reduce the counterweight mass.

But you say you've seen TDs do upwards of 19K plus? On 25% and on a TORNADO prop? I've never had one do that as best I can recall. And I've really tried my best to get one with a good piston to cylinder fit. But that was the days before I learned to use diamond paste and a proper lap. It may be time to dig up that box marked COX on the top shelf. Hey, maybe this killer crank will help.

On the subject of props though, I took the time to gather all the 6 x 3s in my possession and run them on the same afternoon. I was very pleasantly surprised with the Burford prop I got last year. The Burford's know prop technology and like their Taipan prop series, they try to make the pitch true, all the way to the hub. The Taipan blade was taken below the hub but this time, they just made the hub thick enough to accommodate the proper pitch near the hub. I took notes, not available right now, but as I recall, the Taipan did 1000 RPM better than the Tornado and the Taipan has considerably more blade area. And that efficiency showed in the air, with a visibly faster high speed pass and better verticals. This prop needs to be made in all sizes. As far as I know though, it only comes as a 6 x 3 and 6 x 4.

But I'm glad to hear that stock, TD cranks are as good as any. I do plan to make up a pair for a twin, counter rotating set up.

ffkiwi

Andy my experience is solely with F/F use of TD 049's-the fastest I ever had one turning was 25,400 on a DC 5-1/4x 3-1/2 prop-originally intended for the rather sickly DC Bantam sport motor. The TD sounded fantastic-and the model flew like s*** -all revs and no thrust. Incidentally the model was a 6.25oz 1/2A'Witch Hawk'-so it should have gone like stink at that weight. Needless to say I was risking both the ball and socket joint and the prop blades at those revs. fuel was 30%. The rev figures I quoted earlier were for a good TD 049/051 on Cox black 6x3 and 5x3 or Topflite 51/4x3-and were for a bog standard TD-but with the KK timing shims fitted, the right number of head gaskets and 30% fuel. My experience is that Cox (or Bill Atwood or whoever designed the later square tip range of Cox props) got the design bang on-and this is indicated by the number of people who used the 7x3-1/2 prop on F1C's in the late 60's and early 70s-and that prop-in glass or carbon was still available frm some cottage suppliers in the early 80's. I've always thought it was a bit much load for the TD 09 however. Fuel wise I've used up to 65% nitro (but only in PAA load)-and burnt THROUGH a piston-but in all that time never broken a crank.

Hmmn wish I'd known about them (the Lite Machines HD cranks) when they were available-I did avail myself of the Lite Machines Norvel 074s that were going cheap last year-but haven't got around to any testing yet.

ChrisM
'ffkiwi'

Mr Cox

Nice work! How much are you keeping from the original CS engine? Case, backplate and carburator?

Maybe I should try to do something similar on mine, but the case was the worst part of the engine...

SGC

Andy,
Your welcome , glad you made good use if it.
Chriss,
If you look for the No Andy quoted on the auction site , the cranks are still for sale - he has a few.
Stewart

ffkiwi

Ta Stewart-I'll follow up on that.

'ffkiwi'

Japanman

Nice work, man, i had forgotton what a huge window there was in a TD crank! [X(] i could imagine that being a problem...

S

Mr Cox

Hmm, looks like a G-mark needle assembly on the carb?
What a mix then, CS, Norvel, G-mark and Cox...

Still, again showing that if someone would make an effort in these engines sizes there is a lot to be gained compared to what is offered now.

Another thing, I don't have any Tornado 6x3 props, how does the load compare to e.g. cox 6x3 or graupner 6x3?

SGC

The Tornado 6x3 loads the engine less than a cox or graupner, the PB 6x3 (Burford) is thin in blade section with what looks like true pitch.

GrahamC

Hey Andy,

I always enjoy reading your posts, lots of good ideas and info.

Interesting you should post this and just a wee bit of time after Mr. Cox posting his latest problems with his CS 061 with the crankcase with the hole in it.

I have three of the CS 061's one strictly control line and the other RC. I guess I got lucky with the three that I got. One remains unrun and the other two have seen some use. I did nothing special to either, just a good cleaning and a good break in on the bench. In fact they are still not quite completely broken in even now.

I had a 1/2a control line plane out to the field yesterday and it has one of the CS 061's on it. This plane is about 20 years old and a simple all sheet sport flyer - it has had a TD 049, Norvel 049, Norvel 061, AP 061, PAW 80 and now the CS 061 for power. All flew the plane well but the current set up seems to be the best. CS 061 25% nitro 21% oil, self made Turbo plug button (original head used as the clamp) and an APC 6x2 prop and runs about 19,000 to 19,500.

I am starting to like the APC 6x2 prop as well - might not have the pitch speed of the a 6x3 but the engine seems to be happier, runs faster and seems to have lots of thrust.

chees, Graham

AndyW

My Feedback: (1)

Yep, case, backplate, carb AND the headclamp. Plus the prop drive washer etc. The usually non-critical bits but yeah, not in your case. A shame. All my cases are very well done. I'm willing to bet that you have a warranty claim here.

AndyW

My Feedback: (1)

Good observation. I did use the needle assembly from an old G-Mark. For no other reason than because the original was used on the GZ carb that was put on the Picco/Brodak/CS hybrid. I settled on the tornado 6 x 3 as a standard prop long ago because it fell between the Cox and an APC. Some say that you need to run the Norvels fast to get the best power and I've done that, (5 x 2 APC at 25K) but that didn't give me the best flight on the kinds of planes I fly. The Norvels are incredibly versatile. They WILL spin fast and do good work for some on certain applications. But they'll also do a very good job as diesels spinning a Cox 8 x 4 at 11K. That's a Norvel .06 and compares very favorably with most of my .074s which do 11.7K on the same 8" prop. I'd venture to say that the Norvel .06, as a diesel, is superior to any of that size, modern or traditional.

Yes, the Brodak/CS has huge potential. Just making it AAN and using a turbo plug would do wonders.

AndyW

My Feedback: (1)

Graham,

That sounds like you got lucky and got a few good ones. Some of the very early versions I got had cylinders with high and low spots discovered only after I went and lapped a few to suit oversized pistons. This delivered an extra 1,000 RPM on an engine that originally did only 10K on the Tornado.

The Tornados (no longer available) were once THE recommended prop as they were featured in Norvel's catalog. At least for sport RC. As it turns out, the Cox and the Burford, 6 x 3 deliver the best thrust to RPM of all the props tested. I'll have to post a separate thread on that. Two sets of notes have produced some variance that I'll need to clarify with another round of tests.

ffkiwi

Yes the Burford props are good ones-hard to compare with anything else as their layout and blade shape is so different. Of the various ones mentioned thus far I personnally would regard the Tornado and the Graupner as the least efficient of those mentioned. Fully concur with your wish that the Burford ones were available in more sizes. I'd like to see 7x3 and 7x4 for a start-but the existing props were developed for Peter's 0.3cc diesel-and I doubt that this needs anything bigger than a 6". The original 70's Taipan range (which went up to 11 or 12" diameter IIRC) are still partially available in flexible nylon from a new supplier/manufacturer in Australia-I think only 7x4, 7x6 8x4 and 8x6 sizes. Stewart should be able to confirm details [I got mone from a NZ C/L flier]

ChrisM
'ffkiwi'

GrahamC

I had a look for the PB's props with the thought that it would be interesting to get a couple for comparison. That is until I looked at his website and discovered the cost - $16.00 is high enough for two props but not completely unreasonable but the $15.00 postage pushed it up to $31.00 for two props and that is just a bit too much for my wallet I am sure that like all of PB's stuff they are indeed very high quality indeed.

On another note and from same part of the world as PB are some details you might find interesting on using propellers for testing purposes (that is of course unless you have already seen these references). The idea of using standard or calibrated propellers for model engine testing is not new (like that is a ground shaking revelation as it is something we all do to a degree when we tinker and test). However, others have put much thought into the process and to expand on your already vast knowledge of the subject, I offer up the following references from Ron Chernich's marvelous Model Engine News web site:

First the home page:

http://www.modelenginenews.org/

Second, his page on a variety of testing ideas (including details on calibrated propellers)

http://www.modelenginenews.org/techniques/testing.html

And lastly, his page from a series authored by Gordon Cornell detailing the build of a small engine with this page in particular dealing with testing including some formula and propeller constants that can be plugged into the formula. Included in the list of propellers are some of the popular ones for the smaller size engines ie APC 5.7x3 Cox 6x3, Cox 7x3.5 to name a few.

http://www.modelenginenews.org/cornell/p9.html

Gordon's complete series is a good read with lots of interesting details (as is the entire web site).

Starting with the constants presented in the article and the details on the testing page I have given thought to building my own dyno but perhaps I will explore how to calibrate some props on my own the idea being to expand my knowledge of the subject before digging too deep into the dyno thing.

Didn't mean to hijack the thread. I posted some references to a few articles published in the AMA magazine in the thread that Combat Pig started on his Pusher Man 2009 plane so I won't repost them here.

cheers, Graham in Ottawa Canada.

Mr Cox

Thanks for the links. Quite interesting to read, so a cox 6x3 spinning at about 15400rpm or an APC 5.7x3 spinning at about 17200rpm would both require a power of about 0.1 hp, if I read the table correctly. That's a much larger difference in rpm than I thought there would be...

The black cox I have in that size is extremely soft though, guess the data are for the gray ones?

Maybe I'll dig out a few of my last cox props and make a few comparisons myself. I really like the 5.5x4 cox gray but I tend to fly a KB 5.5x4 prop instead as they can handle almost any abuse it seems...

DeviousDave

Did someone say heavy duty cranks? http://cgi.ebay.com/Cox-Tee-Dee-RC-0...4.c0.m14.l1262

AndyW

My Feedback: (1)

I flew the Burford 6 x 3 the other day at 19K plus. Just after, I flew an APC 5.5 x 2 at 24K.

The aircraft flew about the same, verticals were about equal. Flat out full bore on the deck, the APC had a bit of an edge.

The disadvantage to running a smaller prop (that gives the same performance) is that you wear out the engine 25% faster (in this case) and the perceived loudnes is quite a bit more. I'd fly the Cox or Burford at the local park but I'd dare not the APC.

AndyW

My Feedback: (1)

That's the one. The real test will be to run the engine as a diesel on a Cox 8 x 4. [X(] Got to replace the lines in the tank though.

Big Al-RCU

Andy, this has no bearing on the subject, but I found it ironic because when the APC’s first came out lots of us put them on our OS 4-strokes because we thought (were told) they were quieter. Actually, I couldn’t tell much if any difference but wasn’t about to admit it or contradict a popular perception (myth?).
Al

AndyW

My Feedback: (1)

Al,

I think that the scimitar shape with the thin, knife like tips, would likely make a prop quieter. What I meant to convey was that the faster spinning engine delivered a higher pitched exhaust note. A lawn mower is louder, decibel wise, compared to an .049 open exhaust. BUT, the higher frequency of the small engine makes it SEEM louder.

Our brains are trained to respond to higher pitches because that's the range that small creatures, like babies, put out. In fact, all animals respond to the higher pitched sounds coming from their babies. That higher pitch is the result of a smaller voice box, which physics says will put out a higher pitch.

I'm not averse to screaming, small engines, but my experience with diesel has opened up some insights.

It's the difference between this, http://www.youtube.com/watch?v=Cyvb7...e=channel_page on an APC 5.25 X 2 delivering 26K

And this, http://www.youtube.com/watch?v=PRn5i...e=channel_page on a Cox 8 x 4 giving me 10.5K

Both of them, Norvel, Revlite .06

The smaller prop has the edge in HP, static RPM and speed according to my thrust/HP program.

So for a jet type of model, the first way is the way to go.

But for a Sopwith Pup though, imagine how out of place that 26K would sound.

Not louder just more "attention getting"

The Low Stik is neither a jet scale model, nor a Sopwith biplane. Just a versatile, sport plane with a drag profile somewhere between the jet and the biplane. That Stik design, though, sure has a wide speed profile.

Mr Cox

Yes the reactions from others at the field are very different, the small screaming glows are frowned upon while a small diesel that throttles well gets a lot of positive comments.

Can't help but notice that only one engine is muffled in those videos too...

Big Al-RCU

Andy, of course you are correct, and I didn’t mean to imply otherwise, hence my disclaimer that my comment ‘had no bearing on the subject’. It was just the combination of wording (APC and noise) that jogged a 20 odd year old dormant memory cell that I found amusing and was relating to.
Those videos sure tell it all re noise. One of my favorite engines back in the late 40’s was a Drone 29 and to this day the smell of diesel makes me wish that I could hook up a set of 60 ft lines to a Hot Rock. (Have never seen one since, it was a stunt ship flown by Bob Tucker at the Nats.)
Later.
Al

gcb

I believe both the Drone and the Hot Rock occasionally appear at the "Vintage Stunt Championships".

George