Dick, what I wrote was actual visual experience. course that don't mean anything to you. By the way read your crank thing. most of the quality cranks i ever saw were 3 piece machined from forgings, and they were not cantilever ether. won't get into any thing over it tho. But sounds to me that engine makers that support a crank at both ends might jist know more than any of us modelers. otherwise we'd all make them.

let us clarify the double ended support for cranks once and for all .
This is a simple method of dealing with one piece connecting rods.
If I had a small machine shop and I wanted to make a conversion of a industrial engine ,It is the way I would do it.
Otherwise - I have to make that big crankshaft, front case two forward bearings, etc.
The adaption of the industrial engine -much more simple. shafts and bobs -pressed together
The manufacture of a proper cantilever crank requires some pretty good machining, hardening , a lot of case work-
Same reason the rotary valve is not for the faint of heart - .
It takes a hell of a lot more work and capital to do THAT job- but then who want's a rotary valve anyway ------?
Guess ----

Dick, Seems to me that the same tolerences are in a dble ended crank as you are claming for a cantilever. in fact they may be closer for a full crank seeing as how both ends have to be in complete alignment. also the hardening process whether a full depth or case style does have a bearing on the molecular structure. also the material used in the crank. no matter won't settle this issue anyway.

Boy, howdy.
Reminds me of the Novell vs MicroSoft server wars.

Which is best? There ain't no such animal. Too many variables. Starting with production and ending with application.

I'm a ZDZ owner. I read a lot of good things about them on the forums, the price was right, the RCShowcase people friedly. It may turn about average and I really don't care. It's going to be fun flying the big warbird anyway. Actually, I'd have preferred a rebuilt Pratt & Whitney R2800 but I heard there might be weight problems.

No big store of expertise here, just wanna have some fun. And boy, is this thread fun.

BTW, Novell lost to MS maketing, but it had the best product. Maybe still does, don't know 'cause now I'm an MCSE.

Roger

It's getting a little quiet here so I'll ask a question of the Taurus users. Which part(s) of the Taurus 2.6 engine are unique to Taurus? Which ones did they design or manufacture?

Anything beyond the crankcase and propwasher?

Did they design the crankshaft or conrod or are those parts shared with other industrial engines?

When Taurus users describe the engine as being a jewel of machining, are they refering to the crankcase?

Is that it?

A lot of technical data here, but just about all engines will not wear out, but will die in a bad crash. So, I say find a smooth engine in the size (cc) and weight you want and go with it. Captin John

Gee, I haven't hurt an engine in a crash in the last 12 years. That one was a switch harness that quit, causing the trainer to go in at full bore into the asphalt. The poor little Enya 45 was never the same.

Diablo: I bet you never wore many gas engines out either. John

Actually I have worn a few glow motors out. A couple of YS 1.20 motors and a few others. They get to the point where it doesn't make sense throwing more money in them for repairs. Since liners and pistons cost so much, the glow engines become kind of disposable.

Think about it..The reason most, if not all, "industrial" engines use a double ended crank is because of the need for a magneto..The output end of the crank(except for a few weed eaters) is made for a clutch or a pulley..Not normally possible on the end with the magneto flywheel on it..A cantilever crank, with the bearing on the inside and the other one just behind the hub is much more rigid than a pressed together three piece unit..
Some of the Sachs chainsaw cranks have the shaft, web, and the big end rod bearing made as one piece, with the magneto end pressed on..When these are used for model plane engines the mag end is used for the hub, beacuse of the taper. The other end, with no taper, gets cut off, usually flush with the bearing..
Some of the later model 4.2 cranks were ground smaller on the mag end, so on these I had a taper ground on the larger, output side, and cut off the small end...Worked fine, and had a normal large end for the hub..
A normal, three piece crank with one bearing on each end will flex to some extent if an unbalanced prop is used..Doubt it ? Try putting an unbalanced prop on the engine and watch the hub wobble at high rpm..If the engine is designed with two bearings on the front and one on the rear the flex is minimized, more so if the two front bearings are separated..
A properly designed cantilever crank can't wobble at the front because the front bearing is just behind the hub..
If the balance factor of a cantilever crank is EXACTLY the same as a 3 piece there should be no difference is the smoothness..
It is a physical impossibility to exactly balance a single cylinder engine, unless one was built with a balance shaft, like some of the 4 cylinder automotive engines...

Well now we have at least two people in agreement!
Some of the industrial singles I have seen are terrible in this respect-simply because the crank plates/bobs/throws -whatever you want to call the crank arm plates,simply bend as they go.
I seem to recall a particular engine which was released as a single front bearing setup - then switched to a double front bearing setup.
It took courage to make that improvement -but I am certain it was not done just for good looks.

The Precision Eagle "TOC" 4.2 gassers had a very expensive FAG double row ball bearing on the front of the crank, which was a stock 4.2 Sachs 120 SI chainsaw part..Ran fairly smoothly..
I took the front seal out of a G62 and replaced it with a sealed bearing, for 2 on the front....Didn't see much difference..I always recommend this for someone who wants a long extension on the hub...Same thing would work on a G38...
The old Webra Bully gasser had 2 on the front..
Looks like all the bar stock engines would do this..Bearings aren't that expensive....

can anyone explain the differences between the TS AND TSS desigination?,especially on the 2.6.noticed the weight differences between the two.

Hi 2lo,

I just found this out myself recently. The TSS is basically a custom version of the TS. In other words they will custom build you a version to your specs....port timing, polishing, compression, intake, you name it and they will do it for you...of course it won't be cheap, but it would be a really cool one-off motor. It's a service that's tempting me, even though I have no good reason to do it except that I love motors.

I have no idea why they show a weight difference. You'd probably have to ask them.

For an example, this would be a great service for someone that needed a race engine built. For typical R/C applications there should be no reason to need one of the TSS's.

Bill

porting one of the chain saw engines could be a challange- The ones I have looked into, did not offer much in the way of flow increases-
One can shift ports up -or with great care and work - down.
This is why I like engines with a lot of built in flow potential.
In all my years (too many) of poking into engines - I see the most performance goes along with the best breathing setups.
If tho - one takes a good breather and stuffs it up with a Pi--poor exhaust setup - then the breathing improvements are a waste of time.
The industrial engines were purpose built and the guys who did them really did one fine job in most cases - They were not high performance engines de tuned for sawing logs.
solid ,durable, reliable. You bet.

Hi Dick,

First I want to preface this post by stating that I highly regard Dick's opinions and information, even though I don't always agree with his conclusions.

Let's start with the stuff I agree with you on:

>>If tho - one takes a good breather and stuffs it up with a Pi--poor exhaust setup - then the breathing improvements are a waste of time.

Agreed. The higher tuned a motor is, the more critical the exhaust system is to maximize the performance.

>>The industrial engines were purpose built and the guys who did them really did one fine job in most cases - They were not high performance engines de tuned for sawing logs.

The statement is literally true, but I do not agree with you on the implied conclusion. Correct me if I'm wrong, but I believe you're saying engines which have any parts off of a chainsaw motor were not intended to be performance motors and they can't match up to a motor with 100% purpose-built parts.....such as the ZDZ.

Like the saying goes "the proof is in the pudding" and I can't see that you have any proof to back up your statements. From all the numbers you post, and numbers posted by other people for the ZDZ40, there is nothing to suggest it has superior power to the engines that have chainsaw parts. In this case, as you know, I believe the Taurus is at the top of the heap here, but I also believe that the BME 44 and possibly even the FPE 2.4(w/ch ignition)(and maybe others) match or exceed the performance of the ZDZ. All three of these engines use "chainsaw" cylinder/piston assemblies. I do not know enough about the construction methods of the FPE or BME, but the Taurus is a purpose built motor that happens to use a high-quality German Mahle piston/cylinder assembly which is also OEMed to other companies for different applications, which I'm sure includes chainsaws.

For people that do not have history on these discussions, understand that I am not putting down the ZDZ, I think it is a really good motor, I just don't see the proof that it is a superior motor. Merely by the fact that it has a rotary-valve induction and uses 100% purpose built parts, does not automatically make it a better engine. Also, I do not agree with your arguments that the cantilever crank is a superior design. I think the primary factor in ZDZ using this design is lower cost of manufacture. Also, though I agree with you that the rotary valve intake and boost port cylinder design is superior on paper to a piston port/dual transfer port motor, I will again say that I have seen no evidence that suggests this potential superiority has been achieved in the ZDZ40.

As far as the "chainsaw" cylinder motors not responding as well to modifications as the ZDZ, I have no proof one way or another....but, certainly all of these engines would respond well to modifying just like any other 2-stroke, from the early days of chainsaw conversions used on karts, to the latest 2-strokes, you can get a lot more power out of them through modification. Of course, what the application is drives what mods are relevant. You certainly would not want a peaky, high horsepower at high RPM motor for doing IMAC sequences, or 3D. In fact, the stock Taurus' have been tuned to produce their peak power at much lower RPM than most of the other brands so it can pull bigger props at higher RPM than the competition.

Whew! I hope I haven't bored people too much with these ramblings. :drowning:

The BME44 is the only one of that bunch I have seen and run and compared -
They all ran great-
The prop sizes they used were smaller -to obtain best performance.

I do NOT like side carbs -they are clunky -to me-and inconvenient to fit in cowls.
If the good old side port was such a bang up idea - then all of the glow stuff would still be a side port.which they were 50 years ago- excuse me 60 years ago.
The piston cylinders on most quality industrial engines enjoy one great advantage - they are the product of a ton of feedback on what worksbestfor the industrial application.
As a nice model engine - this is a great help.
As far as the crank setup - well - The cantilever has it beat all to hell for ease of rebuilding -and all of the ones I have seen run very smooth.
Power ? I have YET to see any 2.4 equal the ZDZ setup -or even come close.

Speaking of rotary induction....... In this months issue of Motocross Action they are featuring legendary dirtbikes from the past. (cool issue....lots of memories were conjured up)

Anyway, in there they have a picture and artical about an old Kawasaki 100 that used rotary induction. They stated that it made more power than most 125s and even as much as some 250s! My dad had one of those when I was a kid. But then they went on to say that Kawasaki abandoned the rotary induction and went to reed valves. I wonder why a giant concern like Kawasaki, or any of the dirt bike manufacturers don't produce a rotary system any more? If it truly is superior you would think racing bikes would use it, but they don't.

Wiz

WIS: Good reply ! Boy if I had the equipment to machine parts, I would make an adapter on back of a zdz 40cc and try a reed valve setup inplace of the rotor valve. Motorcycles have went to reeds because they give more torque(I heard). Also there are hi-performance reed boxes that are avalible. Thanks, Captin John P.S. t The carb sticking out on side of cyl is a pain for cowl setup Then here is the air flow rushing over throat of it to goof up fuel mix

I rode one - went like stink!
Problem was --the rotary valve housing was OVER your right foot.
I trapped my foot once.
The little reed valve setup is much easier to produce and works darn well
-It can also be tucked in, making a smooth compact engine -
Look at all the new two stroke performance bikes.
So why am I not a reed valve advocate?
well they are a step up over the piston port setup-OR the bikes would be piston port setups.
Yes/no?
I do find I can tune the rotary valve setup for perfect midrange -easily -with a pipe.
But if none of this is important to a user - by all means - use whatever setup makes you comfortable- Heck - I used to run a GMC blower on my everyday driver (a 371 at 1.5 to 1) and had no problems . That setup is considered only good for racing but I had no problems.
It also went like a rocket - (it was) a Rocket 88

What I find funny Dick, is how strongly you defend the rotary valve. I'm not arguing against it, but I have a hard time believing in its superiority. I suppose at one time is was a superior design or that old Kaw 100 wouldn't have been as powerful as some 250s.

I have got to believe that today if it were possible to make a rotary valve engine produce significantly more power the Japanese would find a way to incorporate it into their works bikes without having any ergonomic issues. For these guys money is no issue, but having a winning advantage is.

Interestingly, I've seen some cable actuated device called a power valve on bikes recently....I think they were 4-strokes, but I'm not sure. I'll have to go back and have another look.

Wiz

A power valve is used on two stroke motocross bikes to change the exhaust timing for best performance...Not needed in our application....
I have a very early 3W48 twin, rotary valve..The newer ones are reed valve..Not sure why.....

This has always been a controversy. I have a ton of experience with both in karts. They are very close in performance, and they are superior to piston port when taken to the limit, at least in broad power band with good peak power. In other words, a piston port can produce as much peak power, but it won't have the broad power band of the other two inductions.....assuming the engineering is done correctly. This is the potential of the design I previously mentioned.

Dick hinted at the reason that bikes aren't using rotary valves. The carb sticks out the side of the engine, makes it wider, and generally just gets in the way. One of the keys to power in a rotary valve motor is to have the intake tract as short as possible, so having a long tract wrapping around out of the way on a bike would be counter productive.

BTW, Dick, I agree that I have not seen another 2.4 that matches the performance of the ZDZ. I will definitely give you that the Taurus is 1.x cc bigger and the BME is 3.x cc bigger and that will make a measurable, though slight, difference in performance.

The only rear induction reed valve model engines I have seen - hands on - spit back into the fuselage.
The rotarys do not.
Here is a biggie tho - much crowing about low cost and cheap forign stuff keeps croping up.
It is all very strange to me as I do know a bit about production costs
If I was to pick the least expensive way of doing a gas burner - I would use the side port /piston port stuff and make a crank and case.

Next least expensive - add a reed bank-
Then make a new proper cantilever crank-- lastly - build a rotary setup .
The costs for tooling this would eat a one man shop alive!
The 3W 48 is not much of a powerhouse -as you know. I never bothered with this design.
Inasmuch as I like tuned exhausts -and want smooth midrange - So far -I find the rotary valve best for this -
basically the reed setup depends on the change in pressure in the case to operate .
When I try the pipe setups on th reed engine-- I run into backpressure problems .
The reed bank changes timing!
And NOT what I wanted -tho I can get a max power point.
The rotary valve engines love the backpressure and really respond well. \I am working on finding a pipe setup for the reed bank engines which is dead linear on throttle response so far - not done well--flat midrange.
But the rotary - smooth as glass -all the way.
even with severe boosts and high backpressure.
If any of you engine guys can offer any constructive info - please let me know.

I guess I gotta get an airframe suitable to test the little 40 and 50cc gas burners on. I can't afford to buy a bunch of twins to compare my ZDZ 80 against....although I suppose I could look at 3Ws line up of singles to see how one of those would compare.


Wiz