I no longer have the manual for my oldest TT 46, but I certainly recall reading an engine test many years ago that convinced me to buy my first one. That was either 1992, or 1993. The tester (I don't remember who it was) described the engine in considerable detail, & among other things he noted the nickel-plated liner & speculated about its longevity. The price was so much better than the OS engines at the time that I decided to take a chance on one.

I had five OS 46 SF's at that time -- 4 ABC's (actually ABN's) & a ringed SF. The TT 46 absolutely blew them away. I had no trouble with the SF's, but I replaced them with a pair of FX's & a growing collection of TT 46 Pro's. Needless to say, I no longer have any FX's, but I still have every one of the TT Pro's, including the one that ingested its rear bearing. I cleaned the loose metal bits out, replaced the bearing & away it went. Despite scratches on the piston & many dents on the cyl head & piston crown, plus >100 hrs, it is still more powerfull than a quite-new MECOA 46 Tomcat.

I'm a believer.

The only TT sport engine that still uses a chromium plated sleeve is the .36PRO.

All the others are ABN.


Britbrat,

Have you seen a full size engine's piston that succumbed to fatigue?
I have. It broke clean through the oil ring groove.

The crown actually sepatated from the skirt...


Model engines run at a much higher relative load, compared to auto engines.

There is no speed limit where we fly....

With cars, 90% of the time they are at a 20% load, or less.

Cruising at 60 mph takes about 13-19 HP, of the 100-200 the engine can produce.


So model engine pistons are prone to fail much sooner, from metal fatigue.

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Yeah, but if you mounted a dashboard mixture control for the auto engine, how long do you think auto engines would last? <G>

Sure some pistons break. But most of them are OK at the overhaul, most of them can be used for the next overhaul, and the next. I have seen pistons go through about 3 overhauls, with maybe a spacer to close up a widened groove. That is thousands of hours at say an average speed of 2500 revs or about 1/5 the reves our models go. So I would surely expect our model ringed engine pistons to last maybe 1000 hours.

Dar -- I know. One of my hobbies was auto slalom-racing & I used twin-cam Fiat 124's -- 8,000 RPM+ from 125 - 175 HP 1,400 - 2,000 cc engines, which means MUCH greater reciprocating loads than model engines. However, cars are hardly a reasonable comparison. Full scale recip AC engines & auto-based boat engines run at much higher loads than cars & they typically have 1000 - 2000 hr TBO.

While boat engines typically run ~ 4,000 RPM, the recip masses are absolutely gigantic in comparison to model engines, so I don't accept your contention that fatigue is a serious model engine problem. It may very well be the lifetime limiting factor, but the lifetime is plenty long enough, especially considering the low replacement cost (unless it's OS we're discussing -- short life & high cost).

I'm not sure what you are trying to establish. I have 6 TT 46 Pro's with over 100 hr each, & the highest time example is ~ 180 hr. That's the story. They all run very well, despite the high time & every one is a one-flip starter. Performance-wise, my experience is similar to XJet's -- they lose ~ 400-600 RPM from new -- & that seems to go on forever. I don't know what "forever" is, but it is one hell of a lot of air time & I certainly don't plan on buying any more less-than-forever OS engines in that size range.

Perhaps a significant factor is the use of fuel with castor oil lubricant (Omega) -- that's essentially all that I use

That remains to be seen, Ed...

In model engines, the mixture strength is the only control the modeler has over the ignition timing.

The C/R, nitro and glow-plug are all 'given' and cannot be changed 'on the fly'.
Since a lean mixture ignites earlier and burns faster than a rich mixture, what the pilot actually does when closing and opening the needle, is the same as changing the ignition timing.

This is true to some extent in full-size engines, but ignition timing is just ignition timing there...

Fatigue is simply not an issue with model engines as far as determining engine life. Wear over very long periods is all that determines it. Take a ringed engine....after hundreds of hours the ring wears out so you fit a new one and then that very same piston continues on for the next couple of hundred hours. Then you fit another ring

Most performance aware modelers would consider an engine worn-out, when it is down 11% in maximum HP output...
...Which is the condition of a TT Pro is, when it is down 500 RPM, from new...

It is possible that no further wear will occur, since there is nothing to wear any parts down in a loose tapered-bore engine.

Dust and sand, maybe...

If the engine becomes harder to hand-start, as it will be when it becomes loose; it to me needs an overhaul.

In a ringed engine, the force applied by compression and combustion to the ring, on the sleeve, will continue to wear both of them down.

And Brian is correct. The piston will most likely be reusable.

A steel sleeve, or a nickel plated one, will be worn by the ring and will eventually need replacement.

A chromium plated sleeve, like in some older K&B, ST and even an OS, or two, may survive many more ring replacement cycles.

Well 3D fliers tend to be pretty power-aware and I think most are happy to keep using an engine so long as it provides acceptable performance (pull-out from a hover, etc) and reliability.

My 200+ hour TT46 meets all the criteria (including one-flick starts) so I don't consider it "worn-out".

Anyone who's *really* worried about that 10% of power that has been lost is probably really competition-oriented so likely wouldn't be using a sport engine like the TT anyway -- they'd be spending twice as much on a Webra or whatever.

And as for the ABN/ABC issue -- I've got a GMS32 which has a true ABC liner and it's worn out (ie: hard-starting, low on compression and power) after less than 5 hours running. So, a chrome liner doesn't always mean a longer-lived engine -- there's a whole lot more to engine longevity than just the metals used.

Both engines have been run on exactly the same fuel (10% nitro with 20% lube of an 80/20 synth/castor blend).

XJet,


Maybe it is not only the chromium, but also the other materials, fitting, Etc.

MVVS ABC engines last over 100 hours (when properly maintained), before the TDC pinch is gone.

And with the lower price of the P+L+con-rod+wrist-pin+retainers, it would be cost effective to overhaul, while the TT isn't.

Many of my taper bored engines lose the pinch, at least what you can feel with the glow plug in place, in about 10 hours or so of use. That doesn't mean it doesn't have any taper, just that the piston no longer has an interferance fit at the top. They still have excellent compression and seem to run this way a lot longer than it took to wear the piston enough to lose it's pinch. In fact they run a lot better this way, smoother and more power.

I'm not at all sure what the problem is here. My experience with the TT 46 Pro has been nothing short of outstanding. It is absolutely the most user friendly & cost effective engine that I have ever encountered in 50+ yr of modelling.

While, it is not quite the most powerfull 46 general sport engine that I have experienced (amazingly, the horrible Tower 46 is the winner there), it is sufficiently close that it doesn't matter a fig. My 180 hr TT still starts with one flip, holds a slow steady idle & is close enough to a fully broken-in OS 46 AX for power that you can't tell the difference in flight (this is true if they have similar mufflers -- the stock TT muffler is an amazingly inept device -- loud & restrictive). It is still a lot more powerfull than a new MECOA 46 Tomcat. Seems to me that it isn't worn out yet -- probably not even close.

While I agree that TT parts are expensive in North America (and apparently so in Isreal), that is not the case everywhere in the world -- they are cheap in Asia -- making the engine a sure-fire candidate there for re-building -- if it ever wears out. At 200+ hr lifetime (or 400+ hr according to Dr Nitro), I don't care if it wears out. 200+ hr is about 1,000 flights (or an amazing 2,000 flights at 400 hr) -- it doesn't owe anybody anything at that point, plus the case, carb, head & crank are still usefull as spares.


I have owned a lot of engines by numerous manufacturers & in a wide range of sizes & end-use configurations. There are a lot of them that I wouldn't buy twice, but based on my experience to date, I would buy any TT product in a heartbeat.