My go at the Holly Buddy

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nautilus29

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I decided to try and make the Holly Buddy engine. It's going to be my first IC engine, and with it's well designed simplicity I figured it would be a good stepping stone.

I started with the crank case. It slipped my mind to take pictures of the work in progress, so my only pictures are with the part nearly finished. I taped the holes to #4-40 since I have plenty of those taps around. All in all this part wasn't too bad. I ran a speed of around 900 while boring and the finish turned out pretty smooth.

I have some pictures of the tools I used to finish it, and then finally me indicating the bore to put in the final taped holes. I plan on adding some chamfers and polishing up the outside surfaces before final assembly.

20170805_002002.jpg


20170805_002009.jpg


20170805_002526.jpg


20170805_003158.jpg
 
Looking great so far. Keep the pics coming.
 
Thank you for the compliments! I'm in the process of drawing a solid model in fusion 360 so that I can better understand the ports.

ED, is there a certain clearance you aim for between the nose and the prop drive?
 
Hi Nautilus29,
Ed will, no doubt, be along shortly to answer your questions.
I've recently finished building this great little engine so it's still relatively fresh in my mind.
As far as the prop driver to nose clearance is concerned. What I did was to finish machine the nose piece and the external dimensions of the prop driver. When it came to machining the tapered bore of the prop driver I had the bearing and crankshaft installed in the nose piece. I then used that as a gauge. I bored the taper whilst using the nose piece, bearing and crankshaft assembly to visually match the external tapers so that there was a visually pleasing transition between the two parts. No ugly steps. Because there is a .1mm difference on the external taper diameters it all works well.
As far as the porting is concerned, there is one dimension missing.
On sheet 3 bottom right the dimensions from the centre of the bore to the centre of the 20mm slitting saw is not shown. In Eds original build thread, however, he says to cut to a depth of 6mm. Therefore centre of bore to centre of 20mm slitting saw becomes 16.3mm.
Sorry my reply is long winded.
Hope it's of some help.
Steve.
 
fishy-steve said:
Hi Nautilus29,
Ed will, no doubt, be along shortly to answer your questions.
I've recently finished building this great little engine so it's still relatively fresh in my mind.
As far as the prop driver to nose clearance is concerned. What I did was to finish machine the nose piece and the external dimensions of the prop driver. When it came to machining the tapered bore of the prop driver I had the bearing and crankshaft installed in the nose piece. I then used that as a gauge. I bored the taper whilst using the nose piece, bearing and crankshaft assembly to visually match the external tapers so that there was a visually pleasing transition between the two parts. No ugly steps. Because there is a .1mm difference on the external taper diameters it all works well.
As far as the porting is concerned, there is one dimension missing.
On sheet 3 bottom right the dimensions from the centre of the bore to the centre of the 20mm slitting saw is not shown. In Eds original build thread, however, he says to cut to a depth of 6mm. Therefore centre of bore to centre of 20mm slitting saw becomes 16.3mm.
Sorry my reply is long winded.
Hope it's of some help.
Steve.
Click to expand...

Thanks for the information. Glad to get that dimension before I knew I needed it lol! I had a similar process in mind as you when it comes to fitting the assembly together. Only difference is I'm planning on fitting the prop driver to the assembly while it is in the lathe so I don't have to reindicate it.

Did you use brass bushings on your motor? I've been considering adding them to the nose and possibly the connection rod. I'll have to check on that to make sure I have the clearance though.
 
Sorry if my explanation is unclear. The prop driver, after being flipped, was chucked at all times and the nose, bearing and crankshaft assembly were offered upto it.
I didn't bush the nose or the conrod. My engine will never see flight. I made it purely for the fun of it.
The nose bore diameter was reamed 3/8 and the crankshaft shaft diameter was made to suit.
Good luck with your build.
Steve.
 
Last edited:
Yup, S ally C an't T ell O scar H ad A
H unk O f A pple. SOH CAH TOA, got to love trigonometry. That saying was how i was taught to remember those formulas while serving my apprenticeship.

Greg
 
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