Hi Diablo:

First, I'm really not trying here to argue who has the best Web site, only who has the best motors. I think they're all pretty bad, and I would agree ZDZ does a better job than most of the others, though there's still a lot of room for improvement.

>>I haven't heard of any ZDZ owner complaining that he couldn't duplicate the published rpm figures with the same props.

As far as the prop numbers quoted on the Amelung site for the ZDZ 40(Mejzlik 22X10 and 22X12), I haven't seen anyone run either of these props (in the US) they're quoting on this motor. I have found that Amelung numbers are typically with a tuned pipe/can, not the typical pitts-style muffler we run in the US(this opinion is based on numbers on rcfaq.com that they've reported, not their site).

>>They also tell you what exhaust system and length was used.

I couldn't find that on their site, can you tell me where that info is please.

>>The ZDZ motors also have the advantage of a shorter, stiffer, and more durable crank.

Uuuuh, the crank is what I like least about the ZDZ40. They use a cantilever crank that I view as a step to reduce cost, not the optimal setup for one of these engines. Taurus uses a double web, forged, single throw, fully counter-balanced crankshaft. IMHO, this design is vastly superior to the ZDZ cantilever designs, both for strength and lack of vibration.

>>They feature a screw-in prop stud.

If you're talking about the 40, they use use a six bolt prop hub, as is typical on many larger motors, which is of questionable value in this size engine, and a real pain. The Taurus uses a single screw in bolt, so it has the same advantages you were quoting.

>>Replacement bearings are a common size and inexpensive. They cost less than the bearings in an OS 40 FX (under $10 each) .

I don't see this as an asset. It sounds like the engine builder I quoted was right. The Taurus uses very expensive single-row pre-loaded front and rear bearings on the crank. (I've included a picture of the crankcase and crank below)

BTW, after reviewing the ZDZ sites I noticed I quoted the weight incorrectly for the 40. It appears from their numbers that the ZDZ40 is a bit heavier than I thought, and weighs about a 1/2 oz under 4lbs with a pitts-style muffler(assuming 9oz for the muffler) which makes it only 1.5 oz less than the Taurus. They're a lot closer in weight than I thought.

I'd like to emphasize here that I am not trying to put down the ZDZ, only build up the Taurus. The ZDZ is an excellent motor with a lot of potential. I think they do have an advanced design in some areas, such as rotary valve induction, but I also don't like their crank design. Again, I am only talking about the 40, I have not examined the particulars of their bigger motors, which all have excellent reputations.

I am a self-admitted evangelist for the Taurus. I have not known about them for very long, and I have only had one of their motors for a few months, but I've been involved in R/C for decades and have owned a lot of brands of motors and I was so impressed with the Taurus I just had to spread the word.

Hi Kevin:

>>Rear rotary induction which is so smooth in transition and easier to fit in narrow cowls,etc

I agree completely with your view on this....though as far as smoothness of transition, the Taurus has the smoothest and fastest throttle response of any engine I've owned. I have no way to quantify this, or compare it to the ZDZ, but I can't imagine how it could be better.

>>.......If your friend with the opinions on machining and bearing quality is correct the marketplace will find out fast and sites like these will tell all,which is the way it should be isnt it?

You're absolutely right about this, and it definitely hasn't happened yet. I've only heard good things...but ZDZ's also haven't been in widespread use for very long either, so we'll just have to wait and see. Just for clarification, it was not a friend of mine whose opinion I mentioned. It was a well known engine builder/supplier that I have communicated with, and his opinion on this was totally unsolicited. In fact I was singing the praises to him about the Taurus....which kind of fell on deaf ears, since he thinks his motors are the best too....which I agree they are excellent(no more hints). In fact the new motors he's coming out with soon might kick everybody's b..ts.

Bill