# 2 cycle rotary valve engine



## nx06563 (Oct 2, 2019)

I have built several 4 cycle engines and would like to learn about 2 cycle design concepts. I have also looked at  an article on a split single 2 cycle and understand the concepts but don't know 2 cycle design well enough to think about designing one. Port timing is evidently just short of rocket science.

 Does anyone have plans for a 2 cycle with a rotary valve.  I am looking for a design with a disk valve and not a shaft rotary valve.  I built a version of a Jan Ridders engine with a shaft rotary valve and it was a nightmare to get running.

Thanks for taking time to read.

Hogan


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## rklopp (Oct 2, 2019)

The Nalon Viper is a disk valve “Diesel” 2-stroke. Ron Chernich published the plans. I built two, a Mark I and Mark II. They look great, run great, are powerful, and LOUD!  Being compression ignition, they require accurate machining. 

http://www.modelenginenews.org/cardfile/viper.html


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## WOB (Oct 3, 2019)

There is not too much to be found on rear rotary disc valves, but here  is what I discovered: http://modelenginenews.org/index.html
On the index page, scroll down to " Engines" and expand that topic.  You will see "model engine development" and under that will be "Constructing a Replica Super Fury" . Under that, rear rotary disc valves are covered in some detail.  Next, back on the index page, go down to "Design Center" under "Resources"   Look at "Hot Engine Design".  There is useful info on valve timing.  Also look at "Model Engine Development part II".

If you digest all this stuff, you should be able to design your own rear rotary disc valve induction to convert most any conventional model 2-stroke that originally had a shaft valve.     I know of no published plans available for a rear rotary valve glow-ignition engine that have been published.    I was not interested in a diesel, so I did my own.   I successfully converted a Jones 605                                      (   http://www.hemingwaykits.com/acatalog/Jones_605___Colin_Jones.html  ) to rear rotary disc valve and it runs very well.

WOB


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## XD351 (Oct 3, 2019)

nx06563 said:


> I have built several 4 cycle engines and would like to learn about 2 cycle design concepts. I have also looked at  an article on a split single 2 cycle and understand the concepts but don't know 2 cycle design well enough to think about designing one. Port timing is evidently just short of rocket science.
> 
> Does anyone have plans for a 2 cycle with a rotary valve.  I am looking for a design with a disk valve and not a shaft rotary valve.  I built a version of a Jan Ridders engine with a shaft rotary valve and it was a nightmare to get running.
> 
> ...



Some of the  ATOM series of engines ( atom 3 and 5 ) are rotary valve spark ignition two strokes designed by Edgar t. Westbury and he also designed a boxer two stroke with  a rotary valve   ( i think it was called champion ) 







The photos show a version i made from barstock a few years ago -it was the first IC engine i ever built and from drawings i got from a supplier here in Australia , i also bought castings but they were unusable and the plans were almost indecipherable.

I had a look  for my plans of the craftsman but can’t find them but they are available from E&J Winter boulton scale models . Current price was $25au but I can’t say whether they would post overseas .
You could also look around on ebay or the like  and try to pick up a used twin aero engine and base your designs on it , there are many that used rotary valves ( i believe the wasp was one ).
With the craftsman i found the crank design extremely problematic as it is a bolt together job and i found that when the engine fired it would twist and cause the engine to seize - i ended up tig welding it but that led to distortion and a lot of work straightening it , one day i might go back in and make a new crank and silver solder it together .


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## Bazzer (Oct 4, 2019)

nx06563 said:


> I have built several 4 cycle engines and would like to learn about 2 cycle design concepts. I have also looked at  an article on a split single 2 cycle and understand the concepts but don't know 2 cycle design well enough to think about designing one. Port timing is evidently just short of rocket science.
> 
> Does anyone have plans for a 2 cycle with a rotary valve.  I am looking for a design with a disk valve and not a shaft rotary valve.  I built a version of a Jan Ridders engine with a shaft rotary valve and it was a nightmare to get running.
> 
> ...


Hogan

With regard to starting characteristics there really is no difference between a shaft valve two stroke and a disk valve of the same cylinder configuration.

You can get an engine running without resorting to rocket science on inlet porting, exhaust port timing on very high performance two strokes with a tuned length pipe is another thing though.

I have not built complete engines but have built disk valve conversions for high performance two strokes (6.5cc, 4.5 Bhp, 32,000 rpm) I will dig out photos and drawings this evening.

Regards

Barrie


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## lohring (Oct 4, 2019)

This is a little off topic, but I'm in the middle of writing a series on high performance, glow ignition engines.  They cover the history as well as the issues that are important for performance.  The first parts are below:
namba.com/content/library/propwash/2018/october/14/  History
namba.com/content/library/propwash/2019/april/24/  Piston & Cylinder Fit
namba.com/content/library/propwash/2019/october/4/  Head Design

Lohring Miller


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## Bazzer (Oct 4, 2019)

Hogan

Here are a few pictures of the disk valve that I made for the MB40 pylon racing engine, this replaced the rear induction drum valve of this prototype engine, we could never quite get as much power from the rear induction setups as the shaft valve version of this engine.

Lohring

Thanks for the links to your history of high performance glow plug engines, I will read these and get back to you with comments.

Regards

Barrie


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## nx06563 (Oct 4, 2019)

WOW thanks for the response.  You people have made me spend a whole day searching for the perfect project.  I kind of decided on the craftsman after seeing the pictures posted by XD351.  
I found the plans (I think) on an Austrailian web site E and J Winter and have emailed them.

Thanks for all the input.

Another stupid question----
Most of the 2 cycle designs are airplane type motors.  Do the do well adapted to a flywheel instead of a prop?  I have memories of my youth and whacking my fingers starting a Cox 049.


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## Gedeon Spilett (Oct 5, 2019)

the Westbury "Kestrel" 5cc 2 st engine has an admission through rotary valve in the front of the crankdisk, obviously identical to a rear one !
and its "Zephyr" 2.5cc as a rear valve, but I didnt see the plans
http://www.modelenginenews.org/etw/2s/index.html

this picture summarizes what is required to do the conversion...


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## Bazzer (Oct 5, 2019)

nx06563 said:


> WOW thanks for the response.  You people have made me spend a whole day searching for the perfect project.  I kind of decided on the craftsman after seeing the pictures posted by XD351.
> I found the plans (I think) on an Austrailian web site E and J Winter and have emailed them.
> 
> Thanks for all the input.
> ...


Hogan

An airscrew prop has a lot of advantages, as it applies an increasing load as the engine runs faster, up to a point self limiting. A flywheel if the engine wishes will allow revs to rise to an alarming level.

No need to whack your fingers just use an electric starter.

Regards

Barrie


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## XD351 (Oct 5, 2019)

nx06563 said:


> WOW thanks for the response.  You people have made me spend a whole day searching for the perfect project.  I kind of decided on the craftsman after seeing the pictures posted by XD351.
> I found the plans (I think) on an Austrailian web site E and J Winter and have emailed them.
> 
> Thanks for all the input.
> ...



Just remember that the prop is moving air over the  engine so if you run a flywheel you need to  do the same with a fan .
If you are going to build the westbury design i would take a serious look at the crank design!


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## xpylonracer (Oct 5, 2019)

Hi Lohring
May be my system but none of those links work for me, anyone else have problems loading them ?

xpylonracer


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## lohring (Oct 5, 2019)

The last words describe the article's content.  Be sure you don't include them in the url.

Lohring Miller


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## nx06563 (Oct 5, 2019)

Bazzer,  I understand what you are saying about using a prop vs a flywheel, but isnt engine speed controlled by a throtled carburator.

I am lazy and usually use a model airplane carb on my engines.  

Hogan


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## Bazzer (Oct 5, 2019)

nx06563 said:


> Bazzer,  I understand what you are saying about using a prop vs a flywheel, but isnt engine speed controlled by a throtled carburator.
> 
> I am lazy and usually use a model airplane carb on my engines.
> 
> Hogan


Hogan

Yes you will be fine with a carb, keep it rich at the bottom end, I have seen some RC car engines really race away on tick over if too lean, that is the last thing you want on a new engine.

Good luck

Bazzer


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## raildr (Oct 5, 2019)

One of the best books on ALL engines is the *2 Stroke Tuners Handbook*
http://www.amrca.com/tech/tuners.pdf It helped me understand stuff that was beyond my old brain. I worked in a Yamaha shop way back when and Yamaha had manual on two strokes that was very good. 2 strokes amaze me, thing about the Cox TD-10. There was an .049 engine back then that screamed. I missed a chance to visit George Aldrich way back then, he was a wiz with 2 stroke engines.......


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## xpylonracer (Oct 5, 2019)

lohring said:


> The last words describe the article's content. Be sure you don't include them in the url.
> 
> Lohring Miller



My mistake, excellent articles, looking forward to the next issue !!!!

xpylonracer


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## nx06563 (Oct 15, 2019)

Having raced outboard boats with methanol burning 2 cycles in my youth I like 2 cycles.  The only problem was I knew how to work on them but didn't really understand how to modify anything to improve performance.  That was a black science that I paid handsomely for.
My quest for a twingle engine has gotten me more interested in how they work rather than just making one.  First step I guess is to build one before I try to design one.  I found a design in a "Motor Boys" plan book for a 2 cycle diesel airplane engine that looks like a fun build. I guess I will start there and move on to a design attempt after I get it running.  
I leave for AZ for the winter shortly so I will have to leave my shop behind for 5 or 6 months.  I will continue the build of the "Owen Mate"  when I return.  I have converted the design to inches from metric in Fusion 360 and have the crankcase partially done.  

Thanks for all the great input.  I will resume making chips sometime in April and will probably be looking for more info then.

Thanks

Hogan


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## nx06563 (May 1, 2020)

Back from Arizona and spending my Social Distancing time in the basement building the Owen Mate from the MOTOR BOYS book.  Down to the carburetor.  I'm sure I knew at one time but have forgotten.  
Does the hole in the spraybar go up, down,  or sideways?


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## xpylonracer (May 1, 2020)

Best going down in line with the venturi.
2 holes spray bar at 90 deg to the venturi.

xpylonracer


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## nx06563 (May 4, 2020)

Got my Owen Mate done.  Waiting for a propeller to put on it and will build a test stand so I can try it out outside.  Didn't realize at the start I was going to have to become an alchemist to mix fuel for it.  Hope I don't gas myself or blow myself up.
It was a fun build and not too tough.  I do understand the porting far better now so it was worth it.  I will never put it on an airplane so maybe I can retrofit it for a friends tether car.
Ill do a video when and if I get it running.


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## tornitore45 (May 4, 2020)

Nice job.
Mixing you own fuel is not a problem. Finding the ingredient is where you start pulling your hairs.
Try a commercial product, is most likely cheaper than the mismatched quantity of ingredients you need to buy, if you can find them at all.


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## lohring (May 5, 2020)

More than you wanted to know about fuel for model diesel engines.


			AdriansModelAeroEngines.com :: Fuels for variable-compression diesels
		


Lohring Miller


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## awake (May 6, 2020)

You're right, Lohring, that is a lengthy article.

Can we just get the (ahem) _compressed_ version?


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## ALEX1952 (May 7, 2020)

I aggree with tornitore4,5 back in the day the go faster control line or U control flyers, depending on which side of the pond you are, used Amyl nitrate as an additive to there diesel engines, which you could at that time buy over the counter at the pharmacy, I believe it is now a controlled substance and will get you locked up. It may also explain why  my brain is not so sharp in my dotage, maybe due to passive sniffing.


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## nx06563 (May 10, 2020)

OK here I am, I have build the Owen Mate and am waiting for a prop to try and test start it.  The whole process was to get familiar with two stroke design so I could design one for myself.  I don't think I will ever fly an airplane so I want to build a stationary low rpm 2 cycle model.

I have started design of just such an engine with a 1"  bore,  1.25" stroke.  I am to the port timing portion. I intend on a front rotary disk valve.
After all my study I have a design with 120deg intake duration,  120 deg. exhaust port duration, and 100 deg. transfer port duration.

Question for the pros out there is are these port timing numbers proper for such an engine?

Also is there some formula for calculating port area.

Any guidance would be appreciated


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## WOB (May 10, 2020)

IMHO, your valve timing is conservative and won't develop max power.   This site Model Engine Tests
has a multitude of engine tests.  Some of the tests contain specs of the valve/port timing.   

WOB


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## nx06563 (May 10, 2020)

Checked the web site and the tests are all for Model airplane engines turning lots of RPM.  I am looking for around 6000 RPM and easy starting.    I guess power output is not the greatest concern.  Still conservative with those considerations in mind?


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## WOB (May 11, 2020)

It is easy to limit RPM. Just throttle the engine with an undersized carb.   It will also aid starting.   

WOB


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## nx06563 (May 11, 2020)

Do you have any suggestions for port timing since I a placing ports in  the design right now?
Any guidance would be appreciated since this is the first 2 cycle I have designed.  
Thanks for the help.


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## Peter Twissell (May 12, 2020)

message deleted - posted to wrong thread.


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## nx06563 (Aug 1, 2020)

OK, I've got the Owen Mate built and running after making a tighter fitting piston and have progressed on with designing a simple 2 cycle one cylinder with a rotary disk intake valve.
I have things pretty well figured out but need confirmation on port timing.  There is not a whole lot if info out there on 2 cycle port timing but I have settled on the following numbers.  If anyone has advice to give I would love to hear it.  This engine will be a stationary (not airplane) engine with a flywheel.   I am hoping for a top rpm of 6 to 8 thousand and the ability to idle at a reasonable rpm.

Transfer port duration of 124 degrees
Exhaust port duration of 174 degrees
This gives a blow down of 26 degrees
The rotary disk valve will open at 100 degrees before TDC and close at 25 degrees after TDC.
1" Bore
1.25" Stroke 
2.350" long rod

What do you think?


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## nx06563 (Aug 2, 2020)

I have finished building an Owen Mate and have it running after making a new tighter fitting piston. I have moved on to designing a simple 2 cycle stationary (not airplane) engine with a rotary disk intake valve.
I have it designed and have made a few pieces but am not sure of proper port timing for an engine with a flywheel that I want to run at a max of 6 to 8 thousand rpm and able to idle down .  There is not a lot of info out there on port timing so I am looking for someone to critique what I currently am planning.
Here are the numbers
Exhaust port duration 174 deg.
Transfer port duration 124 deg.
for a blowdown of 25 deg.
1" bore
1.25" stroke

What do you think?


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## WOB (Aug 2, 2020)

Some info on port timing of commercial engines can be found here: Ron's Model Engineering and Model IC Engines Index 
On the left side scroll down and click on "resources".  open up "design center" and scroll down to "discussions". The 3rd, 4th, and 5th topics will provide some info.  The topic concerning FRV is equally applicable to RRV as far as timing is concerned.

I wonder about your design approach.  You are wanting to use what is usually considered a high performance induction system on a relatively low RPM 2-stroke. The flywheel will provide no load, so you must be planning to drive some kind of load with the engine.    Otherwise, limiting peak RPM will require running with the throttle mostly closed, so port timing can be very conservative.


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## Steamchick (Aug 3, 2020)

I have no experience  of disc valve 2-strokes, but I seem to remember (from >50 years ago?) of disc valves being a means of getting more power rather than anything else, when compared to simple ported engines. But I recall a test of a road bike - possibly a Grieves or Cotton? Possibly Rotax? - that I think had a disc valve, and had very good low throttle stability, without 4-stroking? Must do some research....!
Of course, the 2-stroke has always been a commercial success as a high-powered engine, rather than clean, fuel efficient, or low revving...
Please tell us me about your project?
Thanks,
K


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## Steamchick (Aug 4, 2020)

Try this for some background?








						Exploring Two-Stroke Motorcycle Engine Design
					

Kevin Cameron explains how three transfer ports, a rotary intake valve, and counter-cone exhaust design put two-strokes on par with the very best four-strokes.




					www.cycleworld.com
				



k


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## Steamchick (Aug 4, 2020)

Also Kawasaki made lots of production bikes with disc valves, until Yamaha out-performed them with reed valves and clever tweaks to their 2-stroke engines. Rotax made disc valve engines into the 1990s... before pollution (exhaust emissions) from total loss oil systems was banned.


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## nx06563 (Aug 4, 2020)

The whole purpose of the rotary valve is for the design challenge not huge power.  Plus it will be easier to change intake timing. My design is a direct drive off the crank.
This is my first design that hasn't partially copied someone else's concept, and a first step to a twingle.  I like different stuff and ease of construction.
Thanks for the input


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## Peter Twissell (Aug 4, 2020)

Ooh - twingle (split single). Now I'm watching carefully.


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## Steamchick (Aug 5, 2020)

One engine that fascinated me, as it didn't use the crankcase for gas flow, was the 180 degree cranked twin, with 2 diameters of piston, so the lower chamber could induct then charge the opposite upper chamber - tried by Suzuki for clean combustion 2-stoke operation. But it didn't take off due to cost and difficulties of the assembly of  pistion rings to bores!
K


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## PRiggs78 (Aug 5, 2020)

Older mechanical designs are cool for their mechanical engineering approach to two stroke.

I like the idea of computer controlled direct injection and lubrication.  This would be a feat on a tiny model engine.


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## Steamchick (Aug 6, 2020)

I have not sketched-out the idea, but as a configuration for a disc-valve twin (180 degree crank) I wonder if there could be a "nice" layout with an enclosed lubricated central bearing on the crank, with the annulus being a chamber with a disc either side so a single carburettor could feed 2 cylinders.... Must get to a drawing board while the neurons are activated!...
K


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## PRiggs78 (Aug 6, 2020)

A twin may get by with a shared crankcase too space. Provided the case volume isn't too high negating any vacuum draw.  There are plenty of twins out there that do this.


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## Steamchick (Aug 6, 2020)

Hi PRiggs, But surely that would have to be a 360 crank twin? - effectively a split single?
K


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## Peter Twissell (Aug 6, 2020)

It depends whether it's a parallel or boxer twin. A boxer with a 180 degree crank or a parallel with a 360 crank can share the crankcase volume.

A split single is something else - two cylinders are each offset from a single throw crank, so that the pistons hit TDC at maybe 30 degrees separation. They share a common combustion chamber. One cylinder has intake ports and the other has the exhaust ports. The design allows for a 2 stroke with asymmetric port timing.


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## Kasey (Aug 6, 2020)

Are there any 2 strokes with 4 stroke style lubrication?


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## Peter Twissell (Aug 6, 2020)

There has been considerable research into this area. Some years back, I saw a design which had oil fed bearings which were scavenged through a second set of oil passageways in the crankshaft, with seals keeping the oil from mixing with the fuel in the crankcase. Ceramic coatings eliminated the need for cylinder lubrication.
Large marine diesels use 4 stroke type lubrication, but don't use crankcase induction. They have supercharger type induction.
See also the Commer TS3 engine.


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## Steamchick (Aug 6, 2020)

PRiggs: Great information: When I commented on a 360degree configuration, I was referring to a parallel twin, as I have never seen a 2 stroke "boxer" - and agree a 180 crank would suit that!
Peter Twissell: I also remember a crank made up with direct lubrication and a host of seals.... - maybe something Yamaha were working on in the 70s with a view to "cleaner" 2-strokes achieving the California emission laws of that era? Having worked on cars' emissions since the late 1980s, more closely post 2000, I am sure that piston ported engines are too limited to meet current laws and have practical power bands, as they rely so much on the gas dynamics for their best (most efficient?) fueling, combustion, heat transfer and scavenging. However, there may be a means of varying the port timing to produce a cleaner 2-stroke of the appropriate size for motorcycles?  But 4-strokes have taken a lead that is probably not commercially practical for anyone to try and achieve with 2-strokes. Money makes a lot of decisions!
Fortunately, we can make models outside of the road vehicles laws...
K


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## Peter Twissell (Aug 6, 2020)

If the 2 stroke has any future in the automotive world, it might be as a range extender. In that application, the engine can operate at constant RPM and load, so it may be possible to optimise porting, exhaust geometry and gas flow for that one, narrow set of conditions.


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## Steamchick (Aug 6, 2020)

Thanks Peter. Good one!
But there are perhaps millions of 2-strokes produced every year for "micro-power" hand tools, garden tools, etc. But even these are now being superceded by re-chargable battery appliances...
Ho hum... Progress?
A good job "us modellers" record history in our models!
K


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