Author Topic: Ohrndorf Valveless 4 strokes  (Read 1025 times)

Offline glorfindel

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Ohrndorf Valveless 4 strokes
« on: March 21, 2019, 08:22:53 PM »
I just got the plans, someone did it???

Offline Admiral_dk

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Re: Ohrndorf Valveless 4 strokes
« Reply #1 on: March 21, 2019, 09:42:04 PM »
If it is the model aero engine I found a short video clip off - it isn't really a valve less design - just a rotary valve => nothing new.

Or is it something different that we haven't seen yet ?

Offline Chester

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Re: Ohrndorf Valveless 4 strokes
« Reply #2 on: March 21, 2019, 09:42:57 PM »
I’m going to have to research about this one. I haven’t heard about it before but I bet it’s going to be an interesting mechanism

Offline glorfindel

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Re: Ohrndorf Valveless 4 strokes
« Reply #3 on: March 21, 2019, 11:22:19 PM »
If it is the model aero engine I found a short video clip off - it isn't really a valve less design - just a rotary valve => nothing new.

Or is it something different that we haven't seen yet ?
Kind of a drum inducted 4 strokes

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Offline glorfindel

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Re: Ohrndorf Valveless 4 strokes
« Reply #4 on: March 21, 2019, 11:23:59 PM »
https://www.engineman.de/en/products-page/plaene/vl-1-10-motor/

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Online Jo

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Re: Ohrndorf Valveless 4 strokes
« Reply #5 on: March 22, 2019, 08:14:54 AM »
 :thinking: That looks interesting I don't have a rotary valve 4 stroke in my collection to build. I do like to make every different type of engine rather than keep repeating the same old, same old design  :)

Jo
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Online Bluechip

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Re: Ohrndorf Valveless 4 strokes
« Reply #6 on: March 22, 2019, 09:54:29 AM »
Can't really see but it looks similar to the 'Cross Rotary Valve' .

https://www.bing.com/images/search?q=cross%20rotary%20valve&qs=n&form=QBIRMH&sp=-1&pq=cross%20rotary%20valve&sc=1-18&sk=&cvid=E41476CEA8704E6EA53793089C609D4A

There have been models made with this arrangement I'm pretty sure.  ( Pascoe ?? )

The (one of ) other design (s) is the 'Aspin Valve'

A description of these are in that book I gave you Jo.   :ThumbsUp:  'Valve Mechanisms for High Speed Engines'   

Back now to sulking .. Still no proper bacon in the shop   :cussing:  I'm not thriving. Damn sure I'm running short of some essential micro nutrients   :'(

Dave




Offline glorfindel

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Re: Ohrndorf Valveless 4 strokes
« Reply #7 on: March 22, 2019, 05:33:29 PM »
Can't really see but it looks similar to the 'Cross Rotary Valve' .

https://www.bing.com/images/search?q=cross%20rotary%20valve&qs=n&form=QBIRMH&sp=-1&pq=cross%20rotary%20valve&sc=1-18&sk=&cvid=E41476CEA8704E6EA53793089C609D4A

There have been models made with this arrangement I'm pretty sure.  ( Pascoe ?? )

The (one of ) other design (s) is the 'Aspin Valve'

A description of these are in that book I gave you Jo.     'Valve Mechanisms for High Speed Engines'   

Back now to sulking .. Still no proper bacon in the shop   :cussing:  I'm not thriving. Damn sure I'm running short of some essential micro nutrients   :'(

Dave
It look like this.

So far, im not impressed with the quality of the plan, but it will be ok.



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Offline Allen Smithee

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Re: Ohrndorf Valveless 4 strokes
« Reply #8 on: March 22, 2019, 07:10:11 PM »
Yes, that's a Cross rotary valve. Back in the 1980s in the early days of model aircraft 4-strokes Dennis Allen (of Allen Mercury and AM engine fame) made a few hundred engines under the "Condor" brand in .91 and 1.2cu in (15 and 20cc) sizes:



The concept works well enough, but the problem making one with "model engineering" facilities is simply getting a good enough seal on the rotary shaft to achieve compression without excessive friction (and the associated lubrication issues).

Someone mentioned the "Aspen Valve" which is another rotary-valve configuration which uses a rotating conical head insert with ports in it (which may or may not include a separate, continuously burning combustion chamber above the rotary valve). Around the same time as the Condor 91 the austrian company Hirtenberger Patronen marketed a pair of Aspen-valve 4-strokes in .21 and a .49 cu in (3.5 and 8cc) sizes.



 They were compact, smooth running and exceptionally quiet, the .21 in particular running like a little sewing machine. But they never solved the lubrication problem and they used to suffer high wear rates. A clubmate had one that would run for 4 weekends with progressively reducing power and then need to go to the service agent (John Haytree) for a rebuild. It would then last another 4 weeks before the next one. Most had the same experience, and I've heard it suggested that it was the warranty claims on these engines which essentially destroyed HP. They were a major brand in model engines at the time, but they all but disappeared.

The Aspen valve configuration has the advantage that the upper surface can be lapped in (like a car engine valve) for an excellent seal with reasonable thermal coupling to the head fins, but establishing effective lubrication was never easy without a separate positive-pumped oil system. They also needed a 90 degree change in drive direction for the valve (usually a vertical shaft with straight gear drive at the top and bevel gears to the crankshaft at the bottom).

€0.00009 supplied,

PDR
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Offline Admiral_dk

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Re: Ohrndorf Valveless 4 strokes
« Reply #9 on: March 22, 2019, 09:58:41 PM »
Yep - just as I thought - nothing new. Nimbus the biggest Danish motorcycle manufacture (back then - now they make vacuum cleaners) designed a totally similar system more than 70 year ago and had exactly the problems Allan describes .... alas it never made it into production.

Offline glorfindel

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Re: Ohrndorf Valveless 4 strokes
« Reply #10 on: March 22, 2019, 10:18:44 PM »
Good info, thx.

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Offline Allen Smithee

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Re: Ohrndorf Valveless 4 strokes
« Reply #11 on: March 23, 2019, 08:25:18 AM »
Thinking about it overnight I remembered that there was another Cross-valve model aircrft 4-stroke - the Webra T4. It was made initially in .91 size:



Webra had initially planned to make this a supercharged engine by routing the induction through the lower crankcase and then on to the inlet valve, using reed valves to try to make the two cycles of crankcase pressure per induction cycle pressurise the induction system. They never made it work, so the production engines omitted the valves. The resulting engine with its large transfer pipe was rather bulky and this restricted its popularity, but it ran well enough. Years later the Japanese company YS produced (and still produce AFAIK) a very successful range of powerful 4-strokes that used this same supercharging principle, so it can be made to work.

Later Webra followed up with a .61 that had a neater enclosed drive belt and more conventional direct induction:



I don'r remember this engine making much inroads into the market which by this time was dominated by OS, Saito and Enya who just made high-quality engines with conventional overhead poppet valves. They may have been less innovative, but they worked!

AS
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Offline glorfindel

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Re: Ohrndorf Valveless 4 strokes
« Reply #12 on: March 23, 2019, 12:34:20 PM »
The sealing part is done with 2 orings at each ends.

Maybe a real seal would be better??


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Offline dieselpilot

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Re: Ohrndorf Valveless 4 strokes
« Reply #13 on: March 23, 2019, 03:57:58 PM »
Those oring just prevent leakage to the outside, mainly leakage to the intake. The seal in question is simply a very small clearance between the rotary valve and head. In production engines this is achieved with silicon aluminum head and chromed valve of brass/bronze.  The expansion rates of these material allows a small clearance over a wide range of temperatures. Rotary valves need to be quite large to compete with poppet valves in terms of power.

The Aspin valve is a very specific design. The only model engine to use it was the Webra T4-.91 The other Webra T-4 (40, 60, 80) used the Cross type. HP VT series are not Aspin, but are a rotary type.

Offline glorfindel

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Re: Ohrndorf Valveless 4 strokes
« Reply #14 on: March 23, 2019, 04:02:03 PM »
Those oring just prevent leakage to the outside, mainly leakage to the intake. The seal in question is simply a very small clearance between the rotary valve and head. In production engines this is achieved with silicon aluminum head and chromed valve of brass/bronze.  The expansion rates of these material allows a small clearance over a wide range of temperatures. Rotary valves need to be quite large to compete with poppet valves in terms of power.

The Aspin valve is a very specific design. The only model engine to use it was the Webra T4-.91 The other Webra T-4 (40, 60, 80) used the Cross type. HP VT series are not Aspin, but are a rotary type.
Got it, thx for the info!

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