Here is a list of all the postings Craig Booth 1 has made in our forums. Click on a thread name to jump to the thread.
|Thread: V-Twin 100cc Design & Build|
Thanks for the info Jason, that's something new i've learnt.
I do have a collet set that i use for the larger (16mm bit), but will look to use them for the smaller also.
Ignorance is bliss. I guess as a newbie I can get away with it..
I presume now that you've hinted that the milling bit should be held in a collet instead for better accurancy?
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.
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.
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
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.
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.
good thing my lathe has a replicator button... going to be needing that a lot on this build
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
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.
parted off overlength, reversed in chuck and faced off to length.
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
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.
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.
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 1/4x32).
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.
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.
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.
Some more work on the head to change the inlet/exhaust connection. I now have a plate connection which will allow me to easily make the manifolds that will be need to be bent to shape to suit the cowl. Manifold will be copper, silver soldered to flange. The lot can then be chromed.
Hi Niels, yes balance will be via all rotary and 2 times half reciprocating mass.I'm pretty sure I have enough space to do this as there will also be the rear crank web. Of course it will not be based on volume as you note above but mass, with the steel of the crank web having a greater mass per volume than the lighter mass of the piston.
Another good think about Autodesk Inventor is that it calculates mass and centre of gravity of all parts based on material, so I will be able to use this rather than trial and error balancing.
Cylinder head altered a little, increased height by 2mm which allows better sleeve support and also slightly larger fins.
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