A” WEAVER “1CC DIESEL ENGINE

[KEITH BEAUMONTParticipant @keithbeaumont45476]

I am a fairly regular visitor to the very informative site, for those interested in model I/C engines, run by Adrian Duncan. http://www.adrianduncansmodelaeroengines .com.   A few months ago I discovered information and drawings for this 1950s design engine on it and the fact that it was possible to make it from bar stock, I decided it was to be my next project. The article mentions it has been made by several of the “Motor Boys” from the late Ron Chernich’s Model Engine News site and includes photos of finished engines. In particular it was the photo of Ken Croft’s engine that attracted me, with its Britsh Racing Green anodised parts, so it is his engine that I have copied.

MOD Edit Weaver Plans

Two sets of drawings are on the site. The original set, all on one page, are from an article published in the, now defunct, Model Maker magazine of June 1952 and are of their time. IE-Hacksaw Crankcase to shape!  The other set of six drawings are CAD and produced by Ron Chernich.  When I first studied these, I thought the Cylinder was too thin around the area that contains the fuel transfer drillings, also, I do not like forward facing exhaust ports and made a mental note to change these.  It is probably an “age thing” as when I came to machine the Cylinder, I followed the drawing dimensions!  If anyone is interested in making this engine, I would recommend doubling the thickness of the Cylinder below the cooling fins and not have the forward facing exhaust port, but increase both sideports forward, to compensate. This eliminates the problem that the Gudgeon pin has two apertures to possibly catch in to, as well as not having oil blast onto the prop when running.  I always taper fit Gudgeon pins, by using the taper on a hand reamer, to make a tight fit one side of the piston.

The fuel transfer drillings are 5 off. Drilled by putting a tight plug into and flush with, the bottom face of the Cylinder. Then drilling down with a No 52 drill at the joint of the plug to cylinder to the required depth. This leaves  five semi-circular grooves after removal of the plug, The drawing notes call for these to  join with a “belt”. No dimensions or a scrap view of this feature is given. There is mention of using a saw shaped tool to produce it. I presume it is a circular groove around the bore so fuel is injected in a complete ring, rather than from the five semi-circular drillings. I decided not to try to cut this groove, as 1) I do not have a tool small enough and of the correct shape and 2) I thought the possibility of cutting through the thin cylinder wall was too risky. Without it, the finished engine starts easily,runs for two minutes on the tank of fuel and with a 9×4 inch APS nylon prop, is running at 5800 RPM, on Technics 1000 fuel, in the attached photo.  Initially, I fitted a 6×4 APC nylon prop and although  it was firing easily, it would not go over TDC whatever I tried. Normally reducing compression cures this, but not this time. No tight spots either. The engine was originally designed for tether car racing. The old drawings include a fly wheel and I wondered if the timing is set up for fly wheel use, so I changed to the heavier 9×4 prop and away it went. Success!

I will probably make a nipple for the fuel pipe, so that I can use the larger tank fitted to the test rig, Then I can have some longer running times with it and a chance to “play” before it runs out of fuel.

Keith.

[KEITH BEAUMONTParticipant @keithbeaumont45476]

[KEITH BEAUMONTParticipant @keithbeaumont45476]

For some reason the link in my  post to Adrian Duncans site is not working.  I have found that if you Google Adrian Duncans Model Engines,it takes you to the latest October issue,which is not yet on his regular site. Adrian is waiting to have surgery and those reguler visiters to his site are probably thinking that the  absence of the October  Editorial is  due to this. The Google version,however says he is having his operation in November and I am sure we all wish him well. keith

[Ramon WilsonParticipant @ramonwilson3]

Another nice result Keith – an engine I often considered but never got around too. Love the green anodising, very pretty.

Good to see you are still making diesels – I’m not machining much if at all these days but am still flying with them (and glows)

Best regards – Tug

[JasonBModerator @jasonb]

Having had this little beauty in my hands at the Midlands show all I can say is it looks even better in the flesh than it does in the photos.

Any progress on the Mill’s?

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Good to hear you are still very active Ramon and thanks for the comments.

Thanks Justin also and it is a 5cc Mills the grey matter is working on.

Watch this space!

Keith.

[derek hall 1Participant @derekhall1]

Believe it or not I bought the drawings and build articles when I was at school in the early 1970’s.

Progress was slow as only could access the metalwork workshop at school in lunch hours. However I did make enough bits of it to look like a real engine. Alas I never had the time or skill as a spotty 16 year old to complete it let alone run it.

I have lost the bits of the engine many years ago now, but still have the drawings and build articles. The main problem I had though was how to profile the rounded shape of the crankcase. How did you do that?

I am going to add this to my “want to make one of those” list, which grows faster than I can cross them off…..

Yours is a great looking engine by the way !

[derek hall 1]

On derek hall 1 Said:

The main problem I had though was how to profile the rounded shape of the crankcase. How did you do that?

An on-line build log by Ron Chernich describes how he “(ab)used” his lathe as a makeshift shaper to round the crankcase.

 

[JasonBModerator @jasonb]

With most of us having mills these days the crankcase could be held on a mandrel and indexed round to cut a series of faccets that can then be blended with a file. Or even just held on a rotatrt table with a long series cutter you could mill the curved profile and just finish off under the lugs.

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Jason, That looks like you took some heavy cuts ! I shaped mine with a chuck in a horizontal rotary table . If you advance the cut by 4 degrees a cut you get a finish that needs only a light touch up with some wet and dry. One thing to remember is to align the leading cutting edge of the cutter with the longitudal centre line at the start and cut towards the facing flange. You then cut right up to the 90 degree flange face. Then reverse the process for the other half.

Derek,  You now have a reason to put it at the top of the list!

I was suprised to read that log of Ron’s using his lathe as a shaper, as I thought he had a decent miil in his workshop.

Keith.

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Thanks MOD for addiing that Link to Adrian’s article on the Weaver.

Keith

[bernard towersParticipant @bernardtowers37738]

I have done a couple of billet crankcase bottoms on my shaper using a 5c indexer, its a nice gentle process and depending on your divisions you get a good finish with very little clean-up.

[jimbo7636Participant @jimbo7636]

Keith, great build on the weaver.  I am studying the plans and I also found the description of the transfer belt a bit vague.  I always model the designs in Solidworks or Fusion 360 so I can verify timing and details before stepping into the shop.  For this design I will post a few views with dimensions of how I intend to make the cylinder with the transfer belt – maybe this forum can improve the plan.

But I also have a question on the venturi.  In the 1952 articles and also in the MEN drawings the internal taper is not defined.  I believe a “No. 000 taper reamer” is the same as a “#3/0 taper pin reamer”  https://drillsandcutters.com/3-0-hss-spiral-flute-taper-pin-reamer/?gad_source=5

but that reamer only has 1/4 taper over 12 inches, so the angle of the taper will be much less than is shown in the drawings.  Can you share what taper you used on each side of the venturi ?  Thanks!

[JasonBModerator @jasonb]

The “repairman’s” taper reamers that I mentioned on HMEM tend to have about a 7degree included angle which looks about right compared to the original drawing.

As the designer was English I doubt he would have suggested the American sizing of taper pin reamers, had he intended the builder to use a taper pin reamer then he would have used the English description which would probably have been 3/16″

[jimbo7636Participant @jimbo7636]

Here is my current take on the cylinder for the Weaver 1cc.  The transfer belt appears to need to line up with the 5 drilled holes.  See what you think and let me know.  I had to estimate the shape of the transfer belt at 0.042 high.

[jimbo7636Participant @jimbo7636]

I like the idea, but I think the repairman’s taper has a small end diameter of at least 0.125 inches, so it would be too big.  The middle part is meant to be cylindrical at 0.110 inches diameter.  Also, I believe tapered pins were standard and around at the time of the article.  But Im not sure.  Thanks for sharing the image.

[KEITH BEAUMONTParticipant @keithbeaumont45476]

On every engine I have made that calls for a tapered Venturi, I use a stadard 2 bladed reamer, made for opening up holes in metal sheet. Included angle 18 degrees. I drill the parallel hole through first, then ream from both ends until the outside edge looks right. I have previously set this out the hard way on paper. The multi bladed reamer that I have also tried( same included angle ) tends to leave a pattern in the metal. Slow revs, about 50 RPM and plenty of oil with the 2 bladed item, works for me. If the Venturi opening is on the large size, I pre drill in a short way with a larger drill, to minimise the work the reamer has to do.

Keith.

[JasonBModerator @jasonb]

I did say one with a smaller end on HMEM

An imperial taper pin has a 1:48 taper which to me is very shallow compared to what is on the drawing. Though the spray bar probably provides all the reduction in cross section that is needed so would probably work OK with just a parallel bore.

[Clive Brown 1Participant @clivebrown1]

The Ron Chernich build log records that he formed the venturi taper with an 000 taper pin reamer, so only a very slight taper compared to the drawing. His engines appear to have run, so perhaps it’s not too critical. I seem to recall that some commercial engines of my youth made do with plain bits of tubing for intakes with no venturi taper at all.

[KEITH BEAUMONTParticipant @keithbeaumont45476]

That drawing of the ” belt ” looks about how I visulised it. I doubt whether performance will be improved by its inclusion . My engine starts easily and is easy to control on the NV. Increasing the thickness of the lower part of the Cylinder, allowing the increase of the diameter of the transfer drillings will probably have more effect.

Keith.

 

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Clive,  When I made a repro Mills 1.3 cc Mk 1 it had the attached fuel tank with straight through venturi. I then made a seperate venturi and N/V with the 18 degree “trumpet”and a nipple to allow a larger fuel tank to be used.  No difference whatsoever was found in any performance.

Keith.

 

[DiogenesParticipant @diogenes]

I think I might have used my ‘prop-driver-reamer’ to taper carbs/inlet before, but as others say it isn’t necessary if a spraybar/NV is present, a straight tract is fine.

I suppose that a tapered inlet does lend the impression of ‘performance’ to a sporting engine, and after all, to many viewers of an engine, a lot of it is about visual appeal..

[jimbo7636Participant @jimbo7636]

I came across this today – regarding the transfer belt.  https://modelenginenews.org/gallery/p16.html

“Weaver was a Joy to build. The drawings were perfect. The only areas that were a bit challenging for me were as follows.

The transfer belt height is very critical. I ended up making a tool to plunge the .030 depth. My first attempt resulted in too low of height at the top of the 45 deg. angle making the transfer duration only about 60 deg. I then went back in with my my tool and raised the to edge about .010. This worked great. As you know the distance from the top of the transfer belt to the bottom of the exhaust ports is very small ( .028 if I recall )”

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