V-Twin 100cc Design & Build

[Ian Johnson 1Participant @ianjohnson1]

This is a great project, looking forward to seeing it all come together and running.

[Craig Booth 1Participant @craigbooth1]

To give a rough idea how the engine will fit in the cowl. The exhaust manifold will wrap around the outside of the cowl curved to the rear.

Ignore the outlet on the other side, I now need to mirror both the cylinder head and cylinder for that side.

[JasonBModerator @jasonb]

Craig, unless you particularly want chromed exhaust stubs you could solder them up from stainless steel and polish to your desired finish.

[Craig Booth 1Participant @craigbooth1]

Posted by JasonB on 12/07/2019 12:33:50:

Craig, unless you particularly want chromed exhaust stubs you could solder them up from stainless steel and polish to your desired finish.

Jason, have never tried silver soldering stainless, but could be a better idea than having to rely on external chrome plating. Also like to try something new.

[JasonBModerator @jasonb]

Not really any different to soldering steel, just use HT5 or Tenacity No5 flux which removed the chrome oxide layer.

[Craig Booth 1Participant @craigbooth1]

Slower progress now that I'm back at work.

Checked the counter bore depth needed for the sparkplug. I am using a small sparkplug type (same thread as a glow plug 1/4×32).

Also realised that the spark lead would foul on the edge of the cylinder so have reduced the spark plug angle to 15deg and also chamfered the fins to give clearance.

[JasonBModerator @jasonb]

You can get some much neater and nicer looking plug tops than those Rcexl ones

[Craig Booth 1Participant @craigbooth1]

Posted by JasonB on 20/07/2019 08:55:35:

You can get some much neater and nicer looking plug tops than those Rcexl ones

yeah, they are a bit plain, but what came with the unit. Will consider changing them but that's a long way down the track.

[Craig Booth 1Participant @craigbooth1]

started to make some chips. Cylinder No.1

2.5" HE30 barstock, machined down to 62.5mm OD. Fins are 1mm width with 2mm space, 7.5mm deep.

[Roger ClarkParticipant @rogerclark]

What type and size plane are you building Craig?

Roger

[Craig Booth 1Participant @craigbooth1]

Posted by Rockingdodge on 27/07/2019 15:54:01:

What type and size plane are you building Craig?

Roger

Rodger, I'm drawing up plans and have it half cut out for a 1920's style racer. Its a mix hybrid between a Gee Bee R3 and Chuck Gratners Riley B design. Wingspan 100", target weight around 14-15kg

[Craig Booth 1Participant @craigbooth1]

parted off overlength, reversed in chuck and faced off to length.

[Craig Booth 1Participant @craigbooth1]

move to the mill to drill the bottom set of holes for bolting to crankcase and milling the octagon faces.

all that remains are the top set of holes, but think I'll leave these until later as they are non-symetrical and also mirrored for each cylinder head bolt pattern.

[Graham Williams 12Participant @grahamwilliams12]

Hi Craig, this is a lovely project and superb CAD drawings, especially the fully rendered 3D images. As an engineer and keen RC aircraft fan I'm looking forward to seeing this running and flying. Do you use Inventor in a professional capacity?

Graham

[Craig Booth 1Participant @craigbooth1]

Posted by Graham Williams 12 on 29/07/2019 22:10:30:

Hi Craig, this is a lovely project and superb CAD drawings, especially the fully rendered 3D images. As an engineer and keen RC aircraft fan I'm looking forward to seeing this running and flying. Do you use Inventor in a professional capacity?

Graham

Thanks Graham, I am an engineer by trade but in a different field (building services – heating,cooling, ventilation, sustainability etc). I don't use Inventor at work but was already familiar with the standard AutoCAD software so it did not take long to teach myself Inventor and is it relatively intuitive

Craig

[Craig Booth 1Participant @craigbooth1]

good thing my lathe has a replicator button… going to be needing that a lot on this build

[Craig Booth 1Participant @craigbooth1]

on to another relatively simple item. The prop thrust.

Turned on lathe with counter bore. Reversed in lathe to add 0.5mm lip so only in contact with inner race of bearing.

onto the mill to blind drill for M5 tapping holes

moved onto side to drill thru for M6 grub screw tappings (both sides) which will marry with flats on the crankshaft.

[Graham Williams 12Participant @grahamwilliams12]

Very nice parts Craig…..

Graham

[EmgeeParticipant @emgee]

Hi Craig, what is the purpose of the recess in the front face of the prop driver ? I would have thought you need as much driver to shaft contact as possible with the method of fixing the drive to the shaft, also increased mounting face area for the prop, IMO a key would offer more security in operation and if also on a taper ensure concentricity of the drive system.

Emgee

[Craig Booth 1Participant @craigbooth1]

Posted by Emgee on 06/08/2019 09:16:04:

Hi Craig, what is the purpose of the recess in the front face of the prop driver ? I would have thought you need as much driver to shaft contact as possible with the method of fixing the drive to the shaft, also increased mounting face area for the prop, IMO a key would offer more security in operation and if also on a taper ensure concentricity of the drive system.

Emgee

Hi Emgee, the recess is for the retaining nut which holds the prop driver to the shaft, the grub screws stop the rotation. Your'e right, a key would be the correct method but at the moment that is outside my experience and skill. The key and retaining nut seems to be the way most manufactured RC plane engines of this capacity appear to be fixed. I can image that this may be a part I may need to remake later in the build. Thanks for the comments.

[Craig Booth 1Participant @craigbooth1]

This weekend I worked on the crankcase. Started with a big block of aluminium 76x76x65 in the lathe off centred and bored the main crank axis hole. All the other work was carried out in the mill.

The edge chamfers I will do later once the cylinder bodies are located. Now I just have 49 M3 holes to tap

[Craig Booth 1Participant @craigbooth1]

I didn't get any photos but when I had the stock in the lathe for the cylinders, I also parted off the 2 cylinder heads after cutting the fins. Being the same diameter it was easier to do while the stock was aligned.

Then moved to the mill to drill and counter bore the mounting holes (M4 bolts), and the 2 central holes which will be used to fix the rocker bracket. These are M3 threaded, but looking at them now I may increase to M4.

All the mounting holes are asymetric due to clearances needed on inlet and oulet holes.

Next I made a basic block to hold the head while the other operations, circlular on one side to match the head, and square on the reverse to hold it in the vice and small rotary table I have.

Fixed in the vice at 15degrees off vertical to drill the 7/32 hole for the sparkplug, tapped at 1/4-32, and counterbored to 12mm for plug wrench clearance.

Moved to vertical in the vice and used 2mm slitting saw to cut fins in the top

Then back to 15 degrees to chamfer the top edge to give plug lead clearance.

[EmgeeParticipant @emgee]

Nice looking fins Craig, all look very crisp.

Emgee

[Craig Booth 1Participant @craigbooth1]

more work on the head today, but first needed to get the rocker support started as I wanted this in place when I drilled the holes in the cylinder head for the valve sleeves so I would get perfect alignment.

Once valve sleeve holes where drilled, fixed the head to the rotary table to mill the flats for the inlet/exhaust ports and to drill the ports.

These ports will need to be re-drilled once the colphos valves sleeves are in place, but the head will need to be anodised first and this cannot be done with any other types of metal present.

[JasonBModerator @jasonb]

It's coming along nicely Craig and just goes to show you can hold milling cutters in a drill chuck

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