Rotary valved engines

This Forum is dedicated to the Hobbyist I.C. (Internal Combustion) Engine Community.

Moderators: Harold_V, JackF

Post Reply
Ben91069
Posts: 13
Joined: Sat May 20, 2006 2:44 am
Location: Dayton, OH

Rotary valved engines

Post by Ben91069 » Sat May 20, 2006 3:17 am

Hi all, I am a newb here, but not as a machinist.

I have been researching developing a roatary valved engine lately. I first came up with the idea back in 1993, but found out that the idea was an old one with a new twist. The biggest drawback using a rotary valve is combustion chamber sealing. Coates Engines has produced working cylinder heads with rotary valves even back then and currently are ready to mass produce them even for some north american manufacturers.

The rotary valve requires a "dry seal" in order to operate. Engine oil required for a valve shaped like a rotating cylinder exposed to the combustion chamber needs lubricated and this mean OIL. Well, I knew you needed something like a ceramic and this is exactly what is being done.

My current idea is to modify the Coates design to allow for a mechanical system for adjustable valve timing. I also would like to know if anyone has experience in grinding industrial grade ceramic, especially silicon nitride using diamond wheels, or anything similar.


My hope is to develop a prototype design, then refine and apply it to a one cylinder, four stroke engine.
Your AD here for $29.95

Steve Nuttall
Posts: 30
Joined: Fri May 26, 2006 8:21 pm
Location: Canada
Contact:

Post by Steve Nuttall » Sat May 27, 2006 6:04 am

I diamond grind Ceramic
We do ball valves for extreme locations

Last one has a 1/2" thick ceramic seeve bonded inside a standard 3" ball valve; then 2 ceramic seats were radius ground and lapped to seal; the ball was 316 stainless steel HVOF sprayed with Tungsten Carbide (0.01 coat) this is also ground and lapped; the thick liner was already in place before grinding the ball; so it was also part of the seal off

Grinding ceramic with a diamond cup wheel is not hard; just spray water on it to keep dust and heat down

magic9r
Posts: 296
Joined: Thu Mar 23, 2006 6:30 pm
Location: Sheffield, England

Post by magic9r » Sat May 27, 2006 5:57 pm

Why rotary valved?

Guest

Post by Guest » Sat May 27, 2006 7:01 pm

magic9r wrote:Why rotary valved?
One the last frontiers of IC engines is to create an efficient valve train. An engine has to produce enough power to run itself, and power left over is net horsepower. The conventional valvetrain uses a lot of energy to run because of the valve design consisting of poppet valves opened by a camshaft and closed by a valve spring. The nature of the valve spring is what makes a conventional valve train inefficient. The valve is under a constant load because of the spring. When the cam opens the valve, it requires more and more pressure as the valve opens to do this. This uses some of the engines power and multiplied by 2 or 4 valves per cyclinder it is easy to see that it wastes a lot of energy.

The reason to use a rotary valve, mainly is that it uses no spring pressure to hold the combustion chamber seal, but rather a tight fit or seal, much like a piston ring. The valve is a shaft that rotates with a port cut into it. As it opens and closes, it functions in much the same manner as a conventional valve with less power loss.

Because of its design, one could utilize it to produce a super efficient engine or a high powered engine with the same economy as its counterpart regarding displaced volume.

Another aspect is that the rotary valve design can be more easily modified to achieve variable cam timing, which tunes an engines airflow more closely to whatever RPMs the engine is running.

Ben91069
Posts: 13
Joined: Sat May 20, 2006 2:44 am
Location: Dayton, OH

Post by Ben91069 » Sat May 27, 2006 7:06 pm

Steve Nuttall wrote: Grinding ceramic with a diamond cup wheel is not hard; just spray water on it to keep dust and heat down
This explains a lot. What I was thinking for a seal would be nothing more than a cylinder shaped seal. One could use a diamond abrasive in a jig grinding machine to do this.

Specifically what do you use to lap in the seal?
Your AD here for $29.95

Steve Nuttall
Posts: 30
Joined: Fri May 26, 2006 8:21 pm
Location: Canada
Contact:

Post by Steve Nuttall » Sun May 28, 2006 6:52 am

Diamond paste
Ingis canada sell it in 18gram tubes
Start with Brown the red; should be good enought

User avatar
SteveM
Posts: 6564
Joined: Mon Jun 27, 2005 6:18 pm
Location: Connecticut

Post by SteveM » Wed May 31, 2006 1:13 pm

magic9r wrote:Why rotary valved?
With no reciprocating mass, RPM will not be limited by valve float. When RPM gets too high, the valves can't close fast enough.

On Formula 1 cars, the valves are actively opened and closed pneumatically. That's how they get 18,000 RPM out of them.

Also why my RX7 (an almost 30-year-old design) got 8,000 RPM in the late 70's/early 80's. No valves.

Steve

magic9r
Posts: 296
Joined: Thu Mar 23, 2006 6:30 pm
Location: Sheffield, England

Post by magic9r » Thu Jun 01, 2006 8:45 am

My question was asked because I can think of no mass production vehicle engine which uses rotary valves so I was wondering why go rotary for a model engine?

The answer citing energy makes absolute sense.

It's also interesting to know that exotic actuation of conventional valves and rotary engines with ports and no valves at all are a solution for high revolutions, although a compressor might scupper any energy saving and the Wankel is really an exotic rotary 2-stroke not needing valves!

Desmo systems with machanical lift & close will also obviate the fixed losses associated with sprung systems but complexity is high!

Regards,
Nick

Ben91069
Posts: 13
Joined: Sat May 20, 2006 2:44 am
Location: Dayton, OH

Post by Ben91069 » Thu Jun 01, 2006 9:50 am

magic9r wrote:My question was asked because I can think of no mass production vehicle engine which uses rotary valves so I was wondering why go rotary for a model engine?

Regards,
Nick

Well, hopefully automakers will have enough sense to incorporate these designs into future engines. Coates engines states on their website they have agreements to mass produce them in the near future, but is shady on the details.

Why do this for a model engine? I guess just for the satisfaction and possibly a test bed for a more enhanced version on a full size engine.

Plus, it would be neat to see running at a model engine show!
Your AD here for $29.95

magic9r
Posts: 296
Joined: Thu Mar 23, 2006 6:30 pm
Location: Sheffield, England

Post by magic9r » Thu Jun 01, 2006 11:18 am

[quote="Ben91069"] Well, hopefully automakers will have enough sense to incorporate these designs into future engines."

Ben, I'm really interested as to how this would make sense for auto manufacturers, aren't non-combustion-engined vehicles the future?

What advantages do you see this delivering for a commercial engine producer over current technology that might warrant the investment in design & production?

Given the development money and class of engineers F1 teams have to play with what valve technology are they using?

I have a sneaky feeling that poppet valves are still with us for a lot of sound engineering & financial reasons & will still be with us while ever we have combustion powered cars.

Regards,
Nick

Ben91069
Posts: 13
Joined: Sat May 20, 2006 2:44 am
Location: Dayton, OH

Post by Ben91069 » Thu Jun 01, 2006 11:55 am


Ben, I'm really interested as to how this would make sense for auto manufacturers, aren't non-combustion-engined vehicles the future?
It makes sense in that they are and will be federally mandated to produce ever more efficient engines. The only non-combustion engine I know of is electric. The problem with electric cars is energy storage, which is why they are building hybrids. The rotary valved engine can work with a hybrid to produce even more efficiency.

What advantages do you see this delivering for a commercial engine producer over current technology that might warrant the investment in design & production?
It will actually save money in design and production over lets say the newest innovation, variable valve timing, which is even more complex than what we already have. The design takes less effort than a newly designed valvetrain and the production costs are lower because of less components.

I have a sneaky feeling that poppet valves are still with us for a lot of sound engineering & financial reasons & will still be with us while ever we have combustion powered cars.
You're probably right. No one ever said that the best ideas usually come to fruitiion, and I am sure there are underlying reasons why it isn't being done, although I believe it can.

Regards,
Nick[/quote]
Your AD here for $29.95

magic9r
Posts: 296
Joined: Thu Mar 23, 2006 6:30 pm
Location: Sheffield, England

Post by magic9r » Thu Jun 01, 2006 4:05 pm

Again, what are actual the advantages for production automobile engines? :roll:

You'd have to give real world details of work showing efficiency improvements for full sized engines, the fact that no racing team even considers them proves that the gains are negligible or even that losses may result.

Call me a nasty old sceptic but rumours and suggestions don't convince me, if someone can quote good data I'll buy it, if not then it's spam perpetuated by the enthusiastically uninformed.

I'm not saying it's cobblers, I'm strongly implying it :wink:

Anyone know what a fuel cell is? :shock:

Regards,
Nick

Post Reply