Lawrence Merlin V12

[peterl95124]

after brazing the arm has to be sawed, then the piece has to be turned and parted. here we see the turning partially done, with the correct amount to turn off the end shown geometrically in the second photo, and finally we part off (note that I switched tool bits because of the tight space!, also the one parted off here doesn't have enough turned off the end, doesn't match the Vee geometry in the middle photo, so its a scrap piece)

 

[raveney]

now make a jig to hold the arm at 80 degrees across the tube
the jig needs to be symmetrical depth-wise because you need to be
able to make both left and right handed "L" shaped rocker arms so
in the second photo hopefully you can see that the channels for holding
the parts are centered in the jig, and the channel for the arm is 1/4" wide
even though the arm is only 1/8" wide. Also hope you can figure out
where the spring clips came from !

very clever method of fixturing
thank you for sharing that

 

[SPOTTER]

Even if it doesn't fully reproduce the real maelin it's really a great job, it would be nice to try a construction.
you are really good

 

[peterl95124]

Here's the jig for silver-brazing the cam follower pad onto the rocker arm, note the "D" shaped cam follower bar stock, which is milled and sawn from 1/4" A2 tool steel rod as shown next. BTW, A2 is a lot easier to machine than I expected, just keep it flooded with oil, but the mystery is how do they make it, since it hardens as it cools so how can it not be already hard when it comes out of the foundry / factory ???

 

[peterl95124]

here's the jig in use, note that the hardening temp for A2 is "bright orange" significantly higher than required for silver-brazing, so once the silver has flowed (at a "dull red") I crank up the heat, then let it air cool (nothing faster or you'll harden the W1 and that still needs to be drilled and tapped !), once you've got your brazing mojo you can even do more than one at a time with this jig, note how far away from the jig the brazing is, otherwise the jig acts as a heat sink and you can't get all of what you're brazing to bright orange even though the silver has flowed. finally you can no longer saw the A2 so dremel abrasive disk to the rescue.

 

[L98fiero]

Here's the jig for silver-brazing the cam follower pad onto the rocker arm, note the "D" shaped cam follower bar stock, which is milled and sawn from 1/4" A2 tool steel rod as shown next. BTW, A2 is a lot easier to machine than I expected, just keep it flooded with oil, but the mystery is how do they make it, since it hardens as it cools so how can it not be already hard when it comes out of the foundry / factory ???

To anneal A2 it is heated in a controlled atmosphere furnace at a rate not exceeding 400°F per hour (222°C per hour) to 1550°F (843°C) and held at temperature for 1 hour per inch (25.4mm) of maximum thickness; 2 hours minimum, then cool slowly with the furnace at a rate not exceeding 50°F per hour (28°C per hour) to 1000°F (538°C). Continue cooling to ambient temperature in the furnace or in air. The resultant hardness should be a maximum of 235 HBW/ Rc22. Annealed O1 is about 220 HBW/Rc20, so not too much difference.
Personally I find A2 to be 'cleaner'/ produces a better finish, air hardens and doesn't warp as much as O1, it can be used pretty much anywhere O1 can.

 

[peterl95124]

Even if it doesn't fully reproduce the real maelin it's really a great job, it would be nice to try a construction.
you are really good

anyone who succeeds in building this inline-4 with four-valves-per-cylinder will be at the head of the line to buy the full Merlin plans. I'd like to see this level of enthusiasm and commitment before I devote the time required to bring the drawings I have up to date and be usable by others. in the mean time I intend to make the inline-4 plans freely available to encourage people to give it a try.

 

[peterl95124]

here's how I drill and tap the end of the rocker arm for the tappet screw
use X-axis to get correct offset from shaft, use Y-axis to get centered in the arm's width, I use a magnifying loupe to do the Y-axis visually
(yes, everyone should have a pair of angle block sets!)
I don't know about you, but I get tired raising and lowering my BP mill table 3" at a time to switch from drilling to tapping and back, so 2nd photo is my solution...

 

[Peter Twissell]

Peter, if you do want to go ahead and create a set of drawings to sell, I could help by modelling and drawing your design in CAD.
I'm a semi retired design engineer. I'm currently building a Whittle V8 and the first thing I did when I received the drawings was to model the entire engine in CAD.
This process allowed me to identify some errors in the original drawings and produce my own drawings dimensioned in a manner appropriate to my machining methods.
Message me if you're interested.
Cheers,
Pete.

 

[peterl95124]

Peter, if you do want to go ahead and create a set of drawings to sell, I could help by modelling and drawing your design in CAD.
I'm a semi retired design engineer. I'm currently building a Whittle V8 and the first thing I did when I received the drawings was to model the entire engine in CAD.
This process allowed me to identify some errors in the original drawings and produce my own drawings dimensioned in a manner appropriate to my machining methods.
Message me if you're interested.
Cheers,
Pete.

Fusion360 ???

 

[Peter Twissell]

Yes, I have F360 on a commercial license.

 

[peterl95124]

Yes, I have F360 on a commercial license.

OK then, as long as what you produce can be imported into a hobby-ist (free license) version.

how about starting with CAD and drawings for the Inline-4, same geometry as the Vee-12, good for practice and a lot less machining, here are some starting dimensions

cylinders are 1.125 center-to-center, and the block is drilled to 1" IDs (for 1:5.4 scale) but with liners the actual bores are 0.938 with 1.000 liner OD (I wanted thicker than scale liner walls)
and the liners have 1.120 flange OD .031 thick that are flush with the block

cylinder/head studs are 0.938 apart at the 1.125 spacing, #5-40 at each end

head & block from 1.5" bar stock, block is 1.5" high x ~5.1, head is 1.25" high x ~5.8, the head is longer than the block in the rear for the bevel gear to the cam shaft.

combustion chambers are a full 1" ID (true to scale) x 3/16 deep for ~ 7:1 CR
valve layout is both int & exh are 0.203 from center line, int are 0.375 apart and exh are 0.500 apart. all are 0.312 diam (true scale would have 0.344 int, but I wanted to keep it simple) with 0.093 stems

I should probably send you photos of my drawings

 

[peterl95124]

Yes, I have F360 on a commercial license.

lets email off-line for photos of drawings, I'm at peterl95124-at-comcast-dot-net

 

[petertha]

Thanks in advance to both Peter's for initiating this. Can't wait to see what results. The model building community will benefit by the outcome!
Agree 100% with Peter - the benefits of 3D CAD in the right hands is really worth it. Not just to vet parts, features, dimensions, sub-assemblies... but it results in so many useful potential drawing perspectives - sections, dimension... which collectively assist modelers with the build itself. I would also add that any useful fixtures employed worthy of consideration as well because often fixtures are derived off the parts (but I'm not the one doing the work LOL). Good luck guys!
(yet another) Peter

 

[peterl95124]

some photos of my 8-40 spark plugs and bits and pieces, and a 10-40 that hopefully more clearly shows how the ground electrodes are cut from the body (by hand using an abrasive cut-off disk on a dremel, argh!!!, I 8-40 drilled&tapped a holder to help holding them still while grinding, and to avoid burning my fingers!)
the small insulators shown are Corian and loctite'd in and haven't had any problems but then I only run the engine for maybe 30~60 seconds at a time for demos at shows, the larger insulator is Macor again just loctite'd in and that's in my Hansen A-frame engine which ran almost continuously for a couple hours at the last BAEM at GGLS open house show with no problems.
hopefully the pictures are self-explanatory but if you have question feel free to ask !

 

[awake]

That is some incredible work - so tiny!! What are you using for the central electrode?

 

[peterl95124]

That is some incredible work - so tiny!! What are you using for the central electrode?

its just .031 stainless wire !

we don't run our engines hot enough or long enough to cause any problems, but I do see platinum and/or iridium wire on eBay so maybe I should start a go-fund-me !.

one of the frustrating (but not actually challenging) aspects is grinding the back side of the 8-40 die so you can thread up to the shoulder, even then you still have to chamfer the hole in the head that the plug goes into.

the machining is all pretty straight forward, the hardest part is grinding by hand the body electrodes from the machined body and then deburring them by hand too. get out your high magnification OptiVisors !!!

 

[awake]

Is the body mild steel, or also stainless? One thought that probably only exposes my ignorance: could you do a small relief cut at the top of the thread to avoid having to grind the die?

Again, just amazing. I don't think I could pull this off, even with OptiVisors! I'd need a quart of tequila to get the courage to try, at which point my fine motor skills would be lacking ...

 

[peterl95124]

Is the body mild steel, or also stainless? One thought that probably only exposes my ignorance: could you do a small relief cut at the top of the thread to avoid having to grind the die?

Again, just amazing. I don't think I could pull this off, even with OptiVisors! I'd need a quart of tequila to get the courage to try, at which point my fine motor skills would be lacking ...

body is also stainless, gasoline engines don't have the same rust problems as methanol engines, so its not strictly necessary, but I use stainless for plugs (and valves) anyway.

I think full size spark plugs either do have a relief cut at the shoulder or use such a thick copper washer that it doesn't need a relief, but I prefer avoiding either of those. IMHO, YMMV, VWPBL, yada, yada, yada...

you're over thinking this, practice makes perfect, and even I start with more parts than I'll need, the mistakes become my "parts display" that I always show along with the finished engine.

 

[awake]

I'm at the stage where at CM10 spark plug is about as small as I want to get.

I had to look up VWPBL ...