Mazda Rotary - what are the issues to be overcome?

[Lendo]

Although I have a preference for the Spur Gear PSRU, that Billrsv4 is developing. I have some information about a likely candidate for those who might want to develop their own Planetary PSRU.

It's from a new Process 273 transfer Case. It's heavier than the Ford C6 . it has a 31 spline Input on the Sun gear.

It is the low range gear for the 4X4 Transfer Case behind the Ford Power Stroke Diesel 7.3 Liter engine (Ratio 2.72:1). It has been suggested to me that it will handle 3 times the output of the engine.

I have no experience with this myself, just passing on the information.
George

 

[Urquiola]

One clarification on rotary housings. The proper term for the housing that contains the spark plugs, and the 'peripheral' (if installed) intake port and the peripheral exhaust port (in pre-Renesis Mazda rotaries) is properly called the side housing. That housing has always been aluminum in the Mazda engines. I mis-used the term earlier (duh) speaking about the *end housings* and center housings, which touch the *sides* of the rotors. Confusing enough that I get sloppy with the terms sometimes, and I've watched rotaries since before my father bought a new 1974 RX4. Anyway, end and center housings are what are available from aftermarket vendors; the side (rotor) housings have chrome wear surfaces, and people rarely have issues with them in aviation applications, unless there's FOD, or damage from broken apex seals (rare except in boosted engines).

I can kinda see why the V belt system might be chosen for a helicopter, with the need for a clutch in addition to the reduction aspect, and the maintenance-intensive nature and complexity of the tensioning system would be a minor addition in a heli. Given your experience with the Robinson system, you could likely make a V-belt system work if you wanted. But I think you will find it quite a bit heavier than other choices, and very few homebuilders willing to deal with that level of complexity and maintenance intensity in a fixed wing a/c.

Charlie

Hi!: I'm not that sure about the definitions you propose. 'Housing' is the central part, the one where plugs are placed (Ford made some RCEs with plugs in the side plates, others with plugs in rotor, Toyota discovered a Glow Plug in leading site improves economy) where the apex seals slip, where the working surface is plated.
The other parts are called simply: 'plates' or: 'side plates', 'front plate', 'rear plate', 'intermediate plate'.
GM had some housings made of iron, this leads to much higher surface and cooling fluid temperatures, increasing risk of a lubrication film failure, but reduces the flame extinction that is main source of emissions at high rpm,
General Motors reported having solved the fuel economy issue of RCE, but not economy and emissions in the same design, never published detailed information.
For the Corvette Rotary engines, they used aluminum housings, as everyone, it is much more conductive of heat, has less weight.
Rotors were made of iron for thermal dilatation purposes, the Renesis, if I remember well, has aluminum rotors, it have less momentum to be overcome when racing the engine, it accelerate faster. Salut +

 

[AIRCAB]

The 13B MSP ( Renisis) has cast iron rotors, very light in comparison to early 13B

 

[Urquiola]

Urqiola,
I would have thought Butanol, had a better energy rating, I don't know about weight.
The narrow surfaces you refer to are referred to a SQUISH areas and the do (as you say) extinguish the flame front. The result is fuel burned in the exhaust.This has been overcome in the RX8 with side exhausts, as the Apex seal carries unburnt fuel into the next combustion event. However side inlets and side exhausts are more restrictive than the Peripheral Ports.
George

I was told by an expert, Kevin Landers of RotaryResurrection, that when Renesis seals broke and detach, as it have no way to be expelled through a Peripheral Exhaust port, make serious damages to engine.
Squish, as far as I know, is fast gas flow when mix is compressed in a very narrow space, between two very close surfaces, it's sometimes used to speed combustion, generate turbulence; Quenching is flame extinction; in RCE, from cold temperatures in combustion chamber walls.
This is why I'd like, theoretically is possible with no big changes or expenses, having a Renesis engine, a single rotor would be easier to modify, keeping the side exhaust ports, totally closing the side intake ports, and having a Rectangular Peripheral Intake Port, controlled by a Twin Peak Reed-Valve, as in the Ford Canada patent CA1045553 CA 1032477; patent CA 1036073 is about a RCE with plugs in the side plates. About Propanol, I collected data; I have no info about Butanol. The widespread use of extremely toxic Methanol may come just from lower production costs. Salut +

 

[Lendo]

Urquiola,
Interesting statement, most broken apex seals will cause damage, perhaps less so with a Peripheral Port. So one must ask, why is it that the Apex seals break, I would suggest they may tend to break at high load and insufficient lubrication and then there is Detonation. Some aftermarket apex seals are guaranteed not to break at all, but that raises other questions. So we are not running a high load at 6,000 rpm and we maintain lubrication one way or another. Carbon seals are good but I've been advised that Ceramic seals are even better.
The 12A thicker seals are stronger, but the thinner 13B seals - seal better.
George

 

[Neil Unger]

The main issues with a rotary is simply cooling. Most try and economise with small cheap radiators. Bare min is 500 cubs for water and 250 to 300 cubs for oil if cooling a turbo. The rotary has little grief compared to others due to sheer simplicity and light weight. Power to weight is approaching a turbine, with only 3 -4 % more fuel than a piston engine. Cost wise in fuel, much less than an engine on Avgas. Here in OZ $1.50 compared to $2.50 a litre plus.( 4 litres to a US gallon) Can be leaned to less fuel than a lycoming, just depends how fast you want to go. The current Time to Climb record to 10,000 feet is held by a rotary at 100 seconds, and will never be beaten with another combustion engine. 550 HP from a 2 rotor rotary. Check it out on U tube.
Neil.

 

[RSD]

The main issues with a rotary is simply cooling. Most try and economise with small cheap radiators. Bare min is 500 cubs for water and 250 to 300 cubs for oil if cooling a turbo. The rotary has little grief compared to others due to sheer simplicity and light weight. Power to weight is approaching a turbine, with only 3 -4 % more fuel than a piston engine. Cost wise in fuel, much less than an engine on Avgas. Here in OZ $1.50 compared to $2.50 a litre plus.( 4 litres to a US gallon) Can be leaned to less fuel than a lycoming, just depends how fast you want to go. The current Time to Climb record to 10,000 feet is held by a rotary at 100 seconds, and will never be beaten with another combustion engine. 550 HP from a 2 rotor rotary. Check it out on U tube.
Neil.

The main issue with rotaries is that people try to fit them to planes that had air cooled engines and thus don't have enough suitable space under the cowl for an engine that requires a lot of water cooling. Design a plane with suitable space for a rotary and it will be a winner. In my case I'm designing a plane that has twin rotary power.

 

[rv7charlie]

The Renesis does have lighter rotors than the 13B, but they aren't aluminum. I *think* Mazda switched from cast iron to steel in the Renesis.

 

[Lendo]

Neil Unger,
I'm located in Brisbane, where are you located as I would like to meet you and have a look at your RSRU -if possible.
George

 

[Neil Unger]

George, I am in Parkes Middle of NSW. I will be in Brisbane to pick up my original mazda engine before Christmas./ Can meet you there and save a trip for you if that suits. Let me know and we can arrange a meeting, Neil

 

[Urquiola]

The main issues with a rotary is simply cooling. Most try and economise with small cheap radiators. Bare min is 500 cubs for water and 250 to 300 cubs for oil if cooling a turbo. The rotary has little grief compared to others due to sheer simplicity and light weight. Power to weight is approaching a turbine, with only 3 -4 % more fuel than a piston engine. Cost wise in fuel, much less than an engine on Avgas. Here in OZ $1.50 compared to $2.50 a litre plus.( 4 litres to a US gallon) Can be leaned to less fuel than a lycoming, just depends how fast you want to go. The current Time to Climb record to 10,000 feet is held by a rotary at 100 seconds, and will never be beaten with another combustion engine. 550 HP from a 2 rotor rotary. Check it out on U tube.
Neil.

About getting rid of heat in a Liquid Cooled RCE, there is an interesting SAE paper 741091 'The effect of selected coolants on metal temperatures in a Rotary Engine', G A Paul, Dow Chemical. It points propilenglycol mixes are better than usual ethylenglycol, that also is very toxic.
An Spanish company, Inquinasa, now owned by Hunstman, produces a propylenglycol based cooling fluid for Solar power facilities, 'Solar57', where 57 is for the % PropylenGycol content, it's probably suited both for Wankel and ordinary engines.
SAE paper 840237, 'Effects of Alcohol Blends on performance of an Air-Cooled Rotary Trochoidal Engine', M Gutman, Syvaro; indicates mixes of 5% and 10% Ethanol in gasoline do much better than plain gasolines, always add at least 1% oil directly into Wankel fuel, the best oil pumps can fail.
'Cooling your Wankel' is a good booklet from Paul Lamar, head of www.rotaryeng.net site.
In ResearchGate, Joe Graymer, you can find my list of selected Wankel RCE references. Having it all will cost you over $4'000, and time for searching and ordering it one by one. Salut +

 

[Lendo]

Neil, I can do that, what might be easier for you is to ring me my number is 07 33515448, you know how times and dates can change. I'm retired so pretty free most of the time.
Another option is to visit me at home I'm at Ferny Grove in Brisbane.
George

 

[cheapracer]

The Renesis does have lighter rotors ... I *think* Mazda switched from cast iron to steel in the Renesis.

Thin wall cast iron, not steel.

The rotary has little grief compared to others due to sheer simplicity and light weight.

I think it's fair in an aircraft forum, where weight is a critical factor, that we sort out this claim that rotarys are lightweight, they are not, nor is their power to weght anything special, which was exceeded a long time ago by any numbers of piston engines.

The original all aluminium 10A, an absolute dog of an engine, but kept my Father in lots of overtime replacing engines under warranty back in the 1960s, was indeed lightweight, but none since.

My suggestion is anyone wants to argue this point, please show a picture of your complete, ready to install rotary complete with oil cooler and radiator (with fluids), on a set of scales, not some mythical number drawn off the internet.

Not here for a fight, I just think that people considering a rotary, most likely because they believe they are lightweight, should dig a lot deeper than some of these threads that tend to be all good news from advocates of them, same with Subaru engines that are NOT lightweight either (post-EA81), but are also constantly claimed to be in forums.

Facts are hard to beat.

PS: I happen to like rotarys, in fact my 2nd car, a Datsun 1000 Coupe, I fitted a 12A single dizzy into it. If I was considering a rotary, a 12A would be on top, the narrower stock apex seals give little trouble, even in PP form, and the lighter rotors are much easier on the stock side gears, that 13Bs do break occasionally. But I guess by now 12As are getting harder to get.

 

[rv7charlie]

4 port Renesis: ~335 lbs for everything, including dual 55A alternators, the stock exhaust manifold and a heavy Aeroturbine muffler. Everything to run on the plane except fluids. I'll try to add a pic of the scales tomorrow. About the same FWF weight as an O320, and a lot lighter than an angle valve IO360.
edit: Pic added showing weight. Hard to see, but engine is sitting on a small ~440 lb capacity platform scale. I piled various hoses, water tank, etc on top of the engine to get this weight. Only thing not there would be a reservoir for 2stroke oil to feed the oil injection pump, but most guys use premix, which would reduce my engine weight by a couple of lbs (removal of the oil injection pump and adapter).

For perspective, most of the older O320 Lycs weigh around 275-285 lbs, bare. Angle valve IO360s weigh around 335 lbs, bare. Configured to fly, you can add a minimum of 30- 40 lbs; likely more. So while I agree that current (bleeding edge) tech piston engines can be lighter than an 'iron block' rotary at the same HP, they are wound pretty tight to do it while the rotary is pretty much loafing at its stock rated HP.

Now, if we could just get Mazda to start production on the 16X, which has 23% more displacement, has the torque curve shifted to a lower rpm, and is about 50 lbs lighter than a Renesis.....

Charlie

 

[AIRCAB]

Thin wall cast iron, not steel.





I think it's fair in an aircraft forum, where weight is a critical factor, that we sort out this claim that rotarys are lightweight, they are not, nor is their power to weght anything special, which was exceeded a long time ago by any numbers of piston engines.

The original all aluminium 10A, an absolute dog of an engine, but kept my Father in lots of overtime replacing engines under warranty back in the 1960s, was indeed lightweight, but none since.

My suggestion is anyone wants to argue this point, please show a picture of your complete, ready to install rotary complete with oil cooler and radiator (with fluids), on a set of scales, not some mythical number drawn off the internet.

Not here for a fight, I just think that people considering a rotary, most likely because they believe they are lightweight, should dig a lot deeper than some of these threads that tend to be all good news from advocates of them, same with Subaru engines that are NOT lightweight either (post-EA81), but are also constantly claimed to be in forums.

Facts are hard to beat.

PS: I happen to like rotarys, in fact my 2nd car, a Datsun 1000 Coupe, I fitted a 12A single dizzy into it. If I was considering a rotary, a 12A would be on top, the narrower stock apex seals give little trouble, even in PP form, and the lighter rotors are much easier on the stock side gears, that 13Bs do break occasionally. But I guess by now 12As are getting harder to get.

I would agree with your claim about the 13B, in regards to package weight, and the power to wiegth. Leaving the 13B-MSP alone, the stock 13B engine parts have not been available over the Mazda counter for a long time! Aluminum plates have been available for about the last 5 to 10 years. These parts do dfop the package weight considerably. The ability to modify this engine for more HP, is legendary ! The 3 moving parts, and dual plugs is appealing also. I see the PSRU the big setback currently.

 

[Lendo]

Cheapracer, I'm with you on the 12A engine, I would like to see that reproduced for smaller cars to improve availability - with modern improvements naturally.

Do you however seem to forget the advancements that Powersport made with their Superlight engine, with their Oven Brazed light steel housings, it was just the cost to produce them that put that on the backburner - now with current technology, Laser Sintering and 3D printing, anything is possible, but again production costs are high still.

Bottom line the Rotary has many possibilities/opportunities to lower weight. The Germans are doing it with a slightly smaller motor with Aluminium housings, they were even in discussions with Mistral at early stages, but Mistral decided to go the Mazda way, I don't know why as they had to make all parts themselves to satisfy the AuditTrail for Certification. This would have been available to them with the German design.

However I do take your point there's little 'off the shelf' and cost effective presently. This may change if I win Lotto.
George

 

[AIRCAB]

Lando, how would you compare the PowerSport brazed housings, with a sprayed coating, to the new style billet alu / cast iron treated replaceable insert from say, BilletPro ?

 

[Lendo]

AIRCAB,
BilletPro is local to me and I have been down to see him. It's a very good but very expensive product. He does the Aluminium Rotors as well, for racing. I don't know if I could trust them in Aviation. Bottom Line there still a lot of weight in the cast Iron insert. He actually had the Mazda Housing material tested and then had the foundry reproduce blocks he could cut from. He does this as Cast Iron tends to hold oil for the Apex seal to run on and I guess he felt the Mazda Iron had a proven materials mix.

This is not a new method, it's been around for a long time now, I first suggested it to someone in the States years ago now.

I had the plates cut from damaged housings and found the weight saving in using a Cast iron insert in Al Housing, to be not enough for all the work involved - hence why their so expensive.

From what I'm hearing the Det-Gun technique on Al. housings is also very good and a lot lighter but also expensive to do. I believe I would currently go that way.

The Powersport Brazed Steel housings were about 1 lb heavier than their Aluminium housings, maybe the Det-Gun Housings some where inbetween.

Future Laser Sintering 3D printing or other 3D printing will eventually be the norm and with more competition the prices will come down.

Apart from that, I don't know what's the most cost effective.
George

 

[AIRCAB]

George, thanks for taking the time to post that info,

Steve

 

[Billrsv4]

Aircab, and All,
The lightest and longest lasting alternate housings and side plates were the Detonation Gun coated aluminum housing and side plates, period. These were used by Mazda iin the LeMans winning so called 26B four rotor. The SIDE plates and ROTOR HOUSINGS were both only aluminum with the coating. These were used in the engine that won the 24 hour race outright, and was promptly banned by the forward thinking FIM.(snark intended) If these parts were so good why doesn't everyone use them? They are astromically expensive. They have only been used in factory specials. Since they have the production tools they can afford to use the diamond grinding tools needed to work the detonation gun coating. To my knowledge the Mazda LeMans racer/s are the only time anyone has spent the time and money to produce parts this way.
Powersport, built several successful versions of their Superlite engine. They always used modified Mazda standard rotor housings. P-ported, and with all external non essential portions removed. The standard housings are reasonably light weight. All of the talk about building light weight Mazda based Wankel rotary engines are refering to the side and end plates. Which in the regular car engine are nitrided cast iron. These were used by Mazda because they were the least expensive way to make them. Powersport experimented with several methods of making the side and end plates. The material they had decided on in the Superlite engine was cermet coated aluminum. This was still somewhat fragile, but the most reasonable weight savings with a reasonable cost. They felt that the cost of the superlite engine was too high to succeed in the Experimental market and shelved the engine. (I can comment about this in the correct forum or by PM) The last side housing they built, which showed great promise, was the CNC machined and oven braized steel side plate. This material allowed the surfaces to be gas nitrided which closely mimic the original Mazda side plates, but being steel and having all exteranous material removed were much lighter. These plates were used in an engine that was given to Raytec the purchaser of Powersport when one of the partners died in a crash. (Not engine related) They may still have them, or have left them on an engine donated to the EAA museum. These were the most promising side/end plates they tried before selling the business.
Bill