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But we don't compare Kia, Hyundai, Toyota etc with Austins.

 

Why would we? When Austin A40s were around Toyota was probably producing engines with similar lifespans or even less (remember the 1950s & the slogan Jap Crap) Kias beginning production in 1944 & Hyundai in late 1967. Bit hard to compare them when none were in Australia to my knowledge at that time.

 

 

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This has been very interesting to me both for aviation and motorcycle engines. Thanks everyone.

I'm fairly satisfied now that possible reasons for piston throwing in < gen4, which I  beleive that I now have a good handle on, have been substantially reduced in Gen 4.  (piston temps, piston typ

This is something I had no idea about. Bloody interesting.   http://courses.washington.edu/engr100/Section_Wei/engine/UofWindsorManual/Graphics/Piston%20Assembly.jpg Figure 6- Pisto

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Why would we? When Austin A40s were around Toyota was probably producing engines with similar lifespans or even less (remember the 1950s & the slogan Jap Crap) Kias beginning production in 1944 & Hyundai in late 1967. Bit hard to compare them when none were in Australia to my knowledge at that time.

 

Well I wouldn't because of course the older engines had problems, and most of them at that, but some people like to compare old aircraft engines, some even radials from the 30s of last century, with the current crop, the inference being the current ones are all good.

 

 

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That's not my experience with my early Jabiru engine. 1998 model, but I have replaced the 2 rear heads on account of how the old ones didn't have enough cooling fins. The front heads are original.   Never had a problem in the air and about 700 hours now. That would be about 100 trips to Alice Springs from here.

 

Once I asked the factory why my engine was left out of the AD's and was told that it was because they had no problems with engines like mine.  It has all the small bolts they have upsized .

 

Maybe the small carby ( 32mm ) protects things? Maybe the epoxy which prevents any prop hammering? Maybe the frequent ( 25 hour ) oil changes? Maybe taking care with the max temps?

 

In about 200 hours, I intend to swap it for a new gen4 engine.

 

 

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$25,000 on a new Rotax, with titanium parts prices.........

 

Finding the box its in cost $200...... Impressive....

 

Discovering they can't be bothered doing a $50 balance of engine internals?

 

Priceless.

 

I expect the Jabiru are balanced, they run like a sewing machine when on EFI, esp the silky six.

 

 

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You could get valves cheaper for a Ferrari engine. And don't  give me shite about low build numbers.

 

One of the most expensive to rebuild engines I know of, a BMW M5 3.6 is a masterpiece and rare. But parts are still cheaper.

 

 

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Its not 50 bucks to do a balance but its not several thousand either. A decent balancer will set you back a lot of bucks 25k plus and up to 100k. It also doesnt take 5 mins to do a balance properly. I know I had my own Schenck balancer for 10 years..it was second hand and cost me 28k back then. It was for balancing model jet turbines I imported and also repaired all brands..when you have a shaft spinning anywhere from 100,000 rpm to 240,000 rpm...you need a accurate balancer that is very sensitive.  So I do know a little bit about balancing.

 

The 915 IS is 141 hp turbo and injected also super expensive...I would think they balance them as the stress on the engine is a lot more when you increase the hp by 40% and start stuffing air and fuel down its throat at nearly twice the amount

 

Some pics of my balancer doing a turbine from start to finish there are a lot of adjustments required between those 2 pictures.left target is compressor end the right target is the turbine end..both ends require adjustment with a grinder. Tough stuff that inconel

 

IMG_0800.thumb.jpg.0fcac1b966374a36cfb5bbce0622e1d7.jpgIMG_0802.thumb.jpg.974d7a3f646e726fafc27522907f1264.jpgIMG_0808.thumb.jpg.a34def240c1040e748bae9e1423714ff.jpg

 

 

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Here is a engine balancer if you havent seen one..this one I did a repair on for a guy back in the day...I did a lot of repairs on CNC machines and balancers..Just checked the geo on the picture  15 march 2003

 

100-0008_IMG_4.thumb.jpg.e9e687e83b6bd2cbf0d35e01a47e55b1.jpg

 

 

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Compared to the dynamic and other forces inside an engine the" usual" out of balance forces are of a low order. Balancing won't significantly affect the engines capability to rev . More counterweighting will but it's not used all the time as it adds weight. and THAT makes the torsional vibration problems worse.  Not having counterweighting makes the cases take more load.  By not balancing for smoothness you are making a risk of the engine feeling rather "nasty" at revs and also things vibrating that shouldn't, linkages exhaust systems carbs etc

 

    Radials MUST have large counterweights as the whole mass of pistons and rods is hanging off the  single crankpin in each row. Strangely enough, till you think about it, the crankpin is less loaded when the engines got  a load on it (Torque produced). Nev

 

 

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This is why a lot of rotax users complain of rough or vibrations around 4800 rpm and sometimes at 3800 to 4200.. we are positive this is because they are not balanced. When we get this trial setup the specifically balanced flywheel is going on a engine that does have a very knarly vibration at 4800...if this clears it up its no brainer

 

 

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Thanks Kyle and Nev.

 

Love the turbine balancer.

 

My mate builds engines and he is anal about balancing to get the best of BMW engine  to do their stuff on road and track.

 

I know they are not quick nor cheap. The $50 is for a factory like Rotax to incorporate in the production line. It could be more but depends on the automation etc 

 

50,000 engines is enough to justify the investment.

 

 

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I hope you guys realise a four cylinder engine will never be truly balanced, perhaps that is why Rotax do what they do.

 

On the subject of part price I feel Rotax is saying we build this engine which will go 2000 hours and we dont want people rebuilding them in the shed and possibly impacting our reputation. Lycoming and Continental at least know their engines will be rebuilt in a licensed (CASA) shop subject to audits. Good luck with the big bore, the welded crank would be a major turn off for me.    

 

 

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You can balance any engine to take away the majority of harmonics and vibration regardless to the number of cylinders. You are balancing the rotating parts not accounting for the power produced and those other forces produced by combustion. If it didnt work or was valuable it would be standard practice for 80% of all engines and certainly 100% of any high performance engine

 

My engine is being rebuilt by a accredited Rotax maintainer who by the way has far more experience at a machining and technical level that is way beyond most "engine builders"

 

The crank is welded purely as a safety precaution of the extra horsepower as rotax in their unfathomable reasoning decided to use a press together crankshaft instead of making a normally machined/ground crankshaft. This welding has been done by most likely the best welder in Australia who does this day in and day out. This is a well known practice for this style of crankshaft all over the world and its not specific to Rotax. many high performance motor bike engines have this done.

 

If you ever have a prop strike in a Rotax there is a special gauge that you must use to check that the crank journals have not moved

 

If Rotax didnt want their engines being rebuilt then why make available all the parts necessary to do it. If that was the case only specific Rotax people would have access to the parts

 

 

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I hope you guys realise a four cylinder engine will never be truly balanced, perhaps that is why Rotax do what they do.

 

On the subject of part price I feel Rotax is saying we build this engine which will go 2000 hours and we dont want people rebuilding them in the shed and possibly impacting our reputation. Lycoming and Continental at least know their engines will be rebuilt in a licensed (CASA) shop subject to audits. Good luck with the big bore, the welded crank would be a major turn off for me.    

 

 

 

I think what they are really saying is this.....

 

"We have learnt from legacy players in aviation to charge like a wounded bull even if our numbers made, costs and actual engineering prowess indicate otherwise. 

 

We have little wish to be a fair price as we own the market bar that pesky Jabiru. We design our products for maximum return via any parts prices, almost complete replacement of the engine in a rebuild cost and parts wise.

 

We are happy to screw you at all stages of ownership and have worked the market to ensure you will happily just buy another engine at even bigger prices when things get close to a big bill.

 

You can trust our research and development guys are developing safer sounding ways to extract more profit from your wallet pain"

 

 

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  • 3 weeks later...

The only guy I know who gave up flying after an engine-out scare had a rotax engine. But for sure we have had some Jabiru engine issues here over the last 20 years or so. There are more Jabiru engines than rotax and I think the proportions of problems are about the same.

Good luck to you Kyle comms, please tell us the results. I have to say that I can imagine cracks forming in the heat effected zone from those welds, but then I'm a really bad welder. Are the cranks heat-treated after welding?

I didn't know that 4 cylinder engines are unable to be balanced completely, but surely it would be possible to have better or worse out of balance? Personally, I want an instrument that reads engine vibration on my panel.

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They even removed the ones in the B 727 so why put one in a U/L ? Anytime your engine's vibration changes from normal investigate it. Don't just hope it will fix itself. Engines can vibrate from many sources some due to power pulses and others due to mechanical issues. A balanced motor will always feel better than one where not a lot of effort was put into it but the internal loads don't vary much by fine balancing it. Your torsional vibrations won't register on the meter as you don't feel them but they can be very destructive on some engines and usually have a critical RPM basis to them.

A flat Four has better balance than an inline four except for the effect of the cylinder offset effect (one bank is further back than the other). Most VEE motors have the offset problem to a lesser extent unless they use fork and blade conrods . Good rubber mounts will help to insulate the plane from the engine's vibrations and you must keep an eye on their condition. Nev

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There are more Jabiru engines than rotax and I think the proportions of problems are about the same.

 

Bruce, I think you will find that there are a lot more Rotax engines out there than Jabiru. About 5 to 1 I think.

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Last figure I saw was over 45000 Rotax aircraft engines have been produced

There are way more rotax engines in service in australia than Jabs

All engines can be balanced to a degree it just depends how much time and money you can throw at it to be done

Yes the cranks have been welded and heat treated to make sure. It is a common practice but very few guys out there can actually do the job properly. The fellow who did mine is certainly the best guy in OZ and possibly one of the top 10 in the world. I was lucky to get him...its not what you know its who you know when it comes to specialist services like this

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If Rotax didnt want their engines being rebuilt then why make available all the parts necessary to do it. If that was the case only specific Rotax people would have access to the parts

 

Actually they DON'T make ALL the parts available unless you are rotax approved.

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Well I just did a complete engine overhaul and every single part was available....I didnt necessarily use all parts from rotax but I got everything priced from Rotax. Some of the parts Rotax sell as their parts are just OEM from other manufacturers

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When you say you know of problems, but cannot talk about them, I wonder who you are really trying to kid. Either you know what the problems are or you are just pissing against the wind.

There was someone on this site some time ago who kept making those types of statements. Haven't heard from him lately, but a friend of his said that he was having mental problems.

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Well I am pretty sure I dont have mental problems and I never piss into the wind..I dont want to say anything too much as it would directly affect my information source...I plead the 5th ammendment even though we dont have one..all I will say is I WAS going to buy a gen 4 6cyl Jab on intial reports and operations but on the current direct info I have....I then spent similar money and rebuilt a rotax even though it has slightly less horsepower

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In other words Yenn...I did put my money where my mouth is because I DO know the facts and my decision was to spend that money where I thought it would be best used for performance and viability AND most importantly reliability I am prepared to live with...IN MY CASE

 

My case may not be someone elses decision..but its MY bum in that aircraft not yours

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That's true and it's YOUR decision. You are not trying to sell something and profit from it either . There's NO harm in doing that but your "unbiased " opinion ceases to exist when you are an interested person... I personally think the 912 80 HP engine will be their best, as time goes on but we probably need bigger motors for the Majority.. The perfect aero engine eludes us. I would fly a plane with a 3 cylinder Anzani up front. One of the worst engines ever, but in the right circumstances. (not over built up areas or steep forested places). and I'd prefer to assemble it myself or see what was done. Having ONE engine means you do have to go down when it stops, so you pick your locality carefully and have" pre thought" procedures if it's unreliable, just as you do when you have more than one engine, where you may manage to keep it in the air if you do everything right. nev

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