60 degree Vee Twin 1.6cc

[Niels Abildgaard]

Hello Ed

Ask the moderator to remove the 1.6ccm in title and stay with us here.
Your engine is more important than racing until you remove that old fourstroke and put in a 500 ccm single crank 2S twin like Hondas last GP engine.200 hp?
Is there somewhere mere mortals can download drawings of the Owen mate ?

 

[edholly]

Thanks Neils, have asked if the thread name can be changed - a little while ago now I must admit.

Ran Sydney Motorsport Park with the Brabham - managed a 3rd and 2 - 4ths with about a 30 car grid, so pretty happy with that.

Now back to the serious stuff !

As the photos show have made a start on the VHOT short for Vee Holly Owen Twin - a cool name I think ...

As stated before based on David Owen's wonderful Owen Mate for bore, stroke, conrod, cylinder and piston shape etc. In fact I ran my Owen Mate this morning first time in quite a while and it turned a 9 x 4 wood at 8,600 and there would be more in it when its fully run in I reckon - pretty good for a 2c engine - and it started within a few flicks after the chumminess had gone from sitting on the shelf.

I have included a photo of how I arrived at a vertical over the crankshaft tunnel - used a protractor I had from sailing navigating days yonks ago. It allows you to visually set up the vertical and measure it through the plastic. I reckon I got within a few thou of perfect.

Anyway the photos tell the story so far - one cylinder hole cut, hold-down bilt holes drilled and tapped and transfer passages made ..

Ed

 

[edholly]

Crankcase done - about 30 hours work.

The 2 pots are left-overs from my build of the Owen Mate some 12months ago - ones I wasn't happy with at the time. Hopefully my skills have improved and I will be happy with the 2 I make this time around. Plan is to blank off No2 pot and run both No1 and No2 in - in No1 pots hole. Anyway thats a couple of weeks away yet.

You can see the pots are staggered this time whereas the Butterfly next to it were inline needing a fork and blade conrod system. This time side by side rods with No1 closest to the flywheel as it will produce the most power.

 

[edholly]

A bit more progress

Getting closer, just contras, tommy bars, venturi, muff hold down holes and a few other little jobs to go.

Plan is to run it as a single with No2 blanked off to run in the piston/cylinders and to find a reasonable setting as a datum.

The photo of the circles is the way I worked out the timing and settled for 115 BTDC to 15 ATDC - just 120 degrees, Can always open it up a bit more. Even this is a compromise as No2's transfer port is obviously open for 60 degrees more than No1. However at least with a shaft induction you can play with it by opening the inlet hole - in the case of the Butterfly being a sideport you couldn't. The closing timing of 15 deg ATDC is also a compromise as the pistons are about neutral for "suck" at around TDC.

My TDC is the mid-way point between the 2 cylinders ie 30 degrees in the middle of the 60 separation.

Hopefully will be close to running it in about a week. I expect it should run with a fair bit of power, David Owen's Owen Mate is quite a powerful engine and this is twice that with but some inefficiencies, but still should be better power than a single .. unlike the Butterfly.

 

[barnesrickw]

Anxious to see it run. Seems you are about to do the "impossible" twice.


Sent from my iPad using Model Engines

 

[edholly]

Finished all the bits today cleaned them in the ultra-sonic twice then assembled what will be No2 cylinder into No1's hole.

Mounted it and it was running pretty after about 15 minutes of flicking. Had it way too rich.

Interestingly it ran backwards really well for the initial more than a prime run, in fact when I backed off the comp and tried to stop it with a rag, it showed quite some power and I had to really back it off to stop it with said rag.

Then it started correct way and ran beautifully consistent till the tank went dry - about 10 minutes. I only upped the comp for short bursts and captured one of those on video which can be found at

[ame]https://www.youtube.com/watch?v=ZI23YNL6mwI&feature=youtu.be[/ame]

It easily ran to 6,000 rpm with a 10 x 6 wood prop and that was without exploring ultimate comp setting or touching the nva from 2 turns out, so it augers well for it to run as a twin after I run in the other cylinder as I am doing here. The other cylinder is a tad thighter than this one, which is why I want it in No1's hole.

So far am pretty happy with the results ... 2nd photo is still oily fresh from running.

Ed

 

[edholly]

For all you waiting to see if it runs ... YES ... it does !!

This morning ran both cylinder/pistons in on No1 position ... No2 gave 6100 and No1 gave 6150 on my rpm meter so give or take both about the same. No1 was a tighter fit than No2, but after about 15 minutes running each, both have good compression seal. After running No1 in last, left it in its hole and put No2 in place and then for the big test ...... well it fired up after about a minute or so flicking and ran really well.

But ......

Only got 6,000 as best and needle valve setting exactly same as on one .... indicating that it is running on only one properly being No1 and No2 is not doing much. The prop is as can be seen a wood 10 x 6 so not too small. Evidence that No1 is "supercharged" is given away by the size of the "smoke" emitted from the exhaust when it fires but doesn't run ... much more than I've ever seen from a conventional engine, that is why I believe that the engine will pull the revs it does "carrying" No2 cylinder - No2 is in effect like a supercharging pump adding to crankcase pressure and released when No1's transfer port opens and it shoots up into that cylinder at the expense of No2 moments later.

Now I can play with it a bit by turning No1 cylinder slightly to blank off the transfer ports incrementally from the crankcase (depending on amount of turn) - as I am sure No2 is just there for the ride the way it is at present. As a matter of fact No2 comp screw was unwinding slowly and it had little effect on the revs.

I think at the end of the day it will be a curiosity more than a hard working engine, nice to build but unlike a horizontal opposed or inline twin with separate crankcase chambers it will always suffer from inherent inefficiencies and No1 getting the lion's share of the crankcase charge.

I do love it though .. !!

Here's a youtube clip of it running.

http://youtu.be/mnUYv40k6NA

and some images taken after its test run.

Ed
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[petertha]

. As a matter of fact No2 comp screw was unwinding slowly and it had little effect on the revs.
Ed

Very nice runner, congrats! I was going to mention the unwinding but you caught that yourself. I've watched too may needle valves do that over the years, I must have a developed eye for it now. (And inevitably it seems to be in the lean/heat/destroy direction not the other way around )

 

[Niels Abildgaard]

Hello Ed
Nice to see.
Instead of squizing transfer port on number 1,try exhaust port.
How many rpm will prop do on a stink normal Owen Mate?
Pure ignorance from my side:Are these modeldiesel engines never run with tuned exhaust pipes?
If they are not,reason can be that exhaust is so cold,ie engine proces is very efficient,that there is not very much left for charging work.Some gas compressors use tuned exhaust:

http://www.c-a-m.com/Forms/Resource.aspx?ResourceID=29cbb5a4-335c-47a6-b9e3-4bbd77083223

 

[edholly]

This will be my final report on the 60 degree Vee Twin design.

Having made 2 engines, one a sideport, the other a conventional shaft induction port and now having had the chance to appraise them with various "experiments" - I can say that the inefficiencies inherent in the plain 2 stroke design cause the engine to only have the power of the single cylinder from which it was derived.

These are my observations.

Sideport

Based on an ML Midge which allows no control over the timing the induction phase of the engine, it actually produces less power than the single cylinder upon which it is based. It will run and run quite nicely if in my case inverted, but weight for power it is only about 40% efficient compared to that single cylinder version - or - power wise 80% efficient as a single but with double the capacity.

Shaft induction

Based on a single again, this time David Owen's wonderful Owen Mate. This engine showed a lot of promise when it was initially run as a single with the No2 hole blanked off. In fact using a 10x6 wood prop as the benchmark, the Owen Mate gave 5,500 rpm and the 2 cylinder/piston combos gave 6100 and 6150, quite a bit more power in what was a bigger crankcase volume and with much more conservative inlet timing. I think the ball bearing at the conrod end of the crankshaft has helped here, but this is very interesting and maybe worthy of some discussion later. However as a 2 cylinder engine the best I could get was 6100, so in fact again the second cylinder was contributing only enough to overcome its friction in my opinion. Further experimentation with blanking off the transfer ports to try to force some of the mixture into No2 cylinder only seen it diminish the power and with 50% blockage it struggled to get 5200rpm. In all cases the No2 cylinder was not firing, or if it was not enough to heat the muff enough to make you let go of it with your fingers, whilst No1 was the opposite. I believe where No2 contributes is with increasing the crankcase pressure meaning that No1 is like being supercharged and the effect is about equal in more power to the loss through friction of the other components.

I did say at the outset that I beieved there was a 50% loss with a 90 degree twin and a 25% loss with a 60 degree twin - now I realise that this was without friction losses - and that the friction losses look like robbing most of the extra 25% so that the end result is 50% loss for the 60degree Vee Twin - or in other words 50% loss from a double 2cc engine gives the same power as a single 2cc engine - which is what we have proven here.

I certainly don't regret going down this path, I now have 2 nice looking engines that actually run, but not with quite the power I was hoping for.

Overall the vibration was not too bad, with double the reciprocating weight you would expect vibration to be worse than a single, but in both cases I tried to remove as much weight around the crankpin as possible and I am sure this helped.

The V-HOT I would class as a success, however the 60 degree Vee twin two stroke diesel design is a definite failure, fun to build, a bit of a curiosity as I said before - but it does look good and as No8 engine now made - it is my favourite so far.

The photo here is of all 8 engines made, left to right back row the first ones then left to right front row the more recent ones.

It is a very rewarding hobby and my next engine will be either a inline or horizontally opposed twin, but meantime I have an idea ...

I believe there are many guys out there that would like to build an engine but just need a bit of help to get started ... thinking along the lines of a BollAero18 and developing a class/clinic online through HMEM where the "pupils" can share ideas, ask questions, and encourage each other to "give it a go"

Engines
L-R back row BollAero 18 - Owen Mate - Mills 1.3 - Holly Modded Owen Mate
L-R front row Holly Sideport - ML Midge - Butterfly - V-HOT

Ed
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[Niels Abildgaard]

Going from 5500 rpm to 6150 single cylinder just by having a bigger crankcase volume is heresy and very exiting and a 35% power gain.
You will probably not be able to leave that engine alone before You have made it behave like well brougth up children ,that is sharing the food more equally.
I at least is looking forward to next chapter of my favourite bedside story

 

[edholly]

Thanks Neils ... hope I haven't disturbed your sleep too much.

About to start on another project, this time an inline twin and again based on the Owen Mate.

It seems to me that the crucial factor in this type of motor is the link between the front and rear crankpins. I have looked at various designs and they are all good, but I want to use a ball bearing at either end of the link and have come up with an idea similar to automotive flywheel attachment.

Might sound simple, but plan on investigating a bolt on (4 x 2mm cap-heads) rear crankpin disk to the interconnect shaft. If I use a 10mm shaft can get a good selection of ball bearings and the 4 cap-heads will fit nicely into the shaft. This way I can disassemble the bits anytime simple as removing a flywheel off a car engine. It is the friction between the mating surfaces due to the clamping forces imposed by the cap-heads that transfers the motion, rather than the strength of the sheer of the bolts, so I think it will work ok.

Anyway worth a try.

Now the next question is do I continue with this thread for the build or start a new one ... Methinks I will start a new one.

Love that Owen Mate design ... this engine will be a sideport, as having learned from the Vee Twin that there is a lot of power with timing about equal either side of tdc, then I don't think anything will be lost by going to this "inferior" type of induction.

Some doodling to get to here.

Ed

 

[GailInNM]

Ed,
Just to poison your line of thought you might look at my inline twin, the Lobo Pup Twin in the downloads section.
http://www.homemodelenginemachinist.com/downloads/lobo-16-cc-twin-cylinder-2-stroke-diesel-161.html
Gail in NM

 

[edholly]

Gail,

Would you believe sheet No.8 was being printed here as you were typing your post !

Great minds and all that.

I spent this morning reading through your build of the engine, and what a wonderful design it is. Having made the Midge and then a Vee out of the Midge - then making the next engine based on David Owen's Mate, then watching a YouTube clip of a Taplin twin starting every time from first flick - my thoughts are with an engine of around the 4cc mark.

I know the Owen Mate design reasonably well now and the figures I got with a cylinder blanked off on the V-HOT compared to the original motor blew my mind. In the No1 hole it ran a full 6-700 revs harder than the original - that got my attention - and in No1's hole the timing gets back to similar to a sideport.

I will study your drawings and look at the ideas you have incorporated into the Lobo Pup. I try not to be a sucker for punishment so will try to simplify things as best I can - seems the crankcase will be a big exercise and will look at how I might might be able to reduce time there - the beam mounts will take a lot of machining, unless I use the power hacksaw to rough them.

Guess its early days yet and I do have some other commitments - so will probably take a while to get this one going.

What do you think of the bolt-on crankpin/flywheel arrangement?

Ed

 

[GailInNM]

Ed,
It's been a while since I looked at the Lobo drawings in detail. When I was starting the design I looked mostly at the Taplin Twin and the Sparey inspired twin that Ron at Model Engine News built. I mostly did not like the induction connecting system on the intake of either of them.

I think your crankpin system will work OK. If it seems questionable you could mill a shallow square in the crankdisk and on the end of the shaft. The screws would still fit in the corners of the square.

If beam mounts are desirable, making the beam mounts as bolt on affair and squaring up the crankcase some you could save a lot of carving. It's not an uncommon practice.
Gail in NM

 

[Niels Abildgaard]

Ed

Please do not be tempted to use the possible parts from the magic V2 engine to make a more mundane inline twin.
The strange thing is that the bigger dead crankcase volume of the V2 house gives much more power when run as a single than Your old, dare I say,well made minimum volume ,standard house.
At least a last test where whole for cylinder 2 is made like a variable volume and the change it during running?

 

[edholly]

Gail, thanks for that ... Neils, Don't worry I won't be pulling the V-HOT apart to rob its bits !

Yes the power increase with a cylinder blanked off is something I want to investigate down the track, it is an impressive increase and I don't think it is down to the ball bearing on the conrod end of the crankshaft - something must be happening inside the engine that causes it. In time will discuss with David Owen and see if he can identify why this is the case - and also the timing is way retarded over the normal Owen Mate.

Which leads me to the next engine, the inline twin - as mentioned based on David's Mate again for bore stroke and cylinder shape. Have been playing around with its configuration and come up with something like the attached drawing composite from David's original OM plans.

The major change will be that it will be a sideport and will breathe through a plenum chamber similar to what I did with the Butterfly. I also intend to delete a couple of the transfer ports from the "downside" of the conrod rotation along with deleting an exhaust cutout nearest the plenum chamber. I think this will still achieve good power, with plenty of torque to swing a large prop. The rear crankdisc will be a bolt on affair and it will have 3 bearings, 2 supporting the interconnect shaft and one in the nose with a plain bearing at the prop drive.

Now to start carving up a piece of 53mm round bar to make the crankcase with integral beam mounts.

I will start a new thread for the inline twin as it really hasn't anything to do with the Vee Twin design.

As for the Vee Twin itself, in reflection a lot of fun work to get to the point where I have to class the design as something that won't work as a simple 2 stroke. I really enjoyed the exercise however and have a couple of nice motors to look at and occassionally run, but the built in inefficiencies mean that they struggle to be as powerful as the single cylinder from which they are derived.

The drawing indicates the sideport induction opening and the measurement to figure out the timing, which will be 119 degrees, a bit down on the OM but about the same as the V-HOT

Thanks to all who have followed the progress ... will start the new thread soon ... and this engine I am sure will be pretty good ..

I hope!

Ed

 

[edholly]

Just read through my thread here and see maybe I haven't explained exactly why this

Common crankcase 60 degree Vee Twin configuration does not work.

In theory it seems like it will - and as someone said recently on another thread, with the closeness of the 2nd piston following the lead one, you would expect it to act like a big single.

Well I can assure you it does not ... unfortunately .. and it took about 3 months of building 2 engines to come up with that conclusion.

The basic reason why - put simply is ....

The lead cylinder gets maybe 80% of the crankcase fuel air mixture - leaving the following cylinder to only get 20% in my opinion. This happens because the lead cylinder's transfer is "supercharged" by the following cylinder's piston descending adding pressure to eject the mixture up the transfer ports.

But

The by the time the following cylinder is ready for it's charge, the lead cylinder's piston is ascending reducing the already depleted pressure as a result of most of it going into the lead one, and so the following cylinder gets virtually nothing.

The fact that the lead cylinder IS supercharged means that it puts out enhanced power and "carries" the following cylinder - but overall power is down.

For lead and following you can substitute No1 and No2

Hope this explains it and helps those in the future who might be tempted to build a 2 stroke Vee twin that it really doesn't work, it will run as a curiosity and is nice to make however, and sure looks good on the shelf !

The Inline Twin thread mentioned above can be found at ...
http://www.homemodelenginemachinist.com/showthread.php?t=23188

Ed

 

[edholly]

Went to the Oily Hand weekend at the Cowra Model Aero Club on the western plains of NSW Australia where you were only allowed diesels (or glo up to 1cc) for most events. All engines had to be UN-muffled so plenty of noise just like when I was a kid at Centenial Park in the heart of Sydney's Eastern Suburbs.

This was the best weekend ... absolutely fantastic.

Glorious sights and sounds from about 50 guys with everything from catapult glider to freeflight - control line - and of course radio. The model of the meeting was the Hearns Hobbies Sportster of which 20 were built or in the throws of with a remarkable 14 in attendance - all beautifully made.

I took the 11 diesels I've made in the last 16 months and it is the first time I've run a lot of them back to back.

I have to say now that this Owen Mate based Vee Twin is the most powerful engine I have made, and although No.2 cylinder is almost there for the ride - its pumping effect on No.1 does mean that the overall power is probably more like a single 4cc diesel. I ran it on a 12 x 4 prop and it turned it pretty fast. Soon after I ran the inline twin of 4cc (although a sideport design) and it was nowhere near as powerful, so I will do a back to back analysis in the next week or so.

I said earlier that it really doesn't work - I think I might take that back now !

Maybe I was a bit harsh in my original conclusions of this motor, and of course it will probably get better with more running too.

It did attract a bit of attention amongst the diesel lovers there too.

Pity poor Jacko had to leave a Schlosser 0.25 in the top of a tree inside a little biplane - at least when it comes down the Club will return it to him ...

Ed

 

[johnny1320]

.


I have to say now that this Owen Mate based Vee Twin is the most powerful engine I have made, and although No.2 cylinder is almost there for the ride - its pumping effect on No.1 does mean that the overall power is probably more like a single 4cc diesel. I ran it on a 12 x 4 prop and it turned it pretty fast. Soon after I ran the inline twin of 4cc (although a sideport design) and it was nowhere near as powerful, so I will do a back to back analysis in the next week or so.

I said earlier that it really doesn't work - I think I might take that back now !


Wow this is interesting, I know it would be a lot of work but what if you were to make a new second cylinder liner with no ports and just used the pumping action of the second cylinder, just a thought