Author Topic: Longboy's "BEST FRIEND FOUR" model gas engine.  (Read 8004 times)

Offline Longboy

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Longboy's "BEST FRIEND FOUR" model gas engine.
« on: March 28, 2017, 06:16:32 AM »
Flathead engines, an old design from the onset of internal combustion. Most notable characteristic is its cylinder head with nothing more than the spark plugs rising up from its surface. No camshaft or rocker arm assembly on top, its low profile stance calls attention to its named type. Valves in block along side the cylinders furnish the breathing.....except in this example! ( :thinking: ...where did you put those valves Longboy?)

The Best Friend Four story coming up now!



« Last Edit: April 18, 2018, 08:23:02 AM by Longboy »
Wadda you mean, "It don't run"???

Offline Longboy

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Re: Longboy's "BEST FRIEND FOUR" crankshaft assembly.
« Reply #1 on: March 28, 2017, 08:29:21 PM »
Here is a photo of another modeler's (PARKSY) crank cradle. Made for his steam engine, I felt the same could be used under a gas engine for my winter shop work. A block could be supported over this cradle by posts or a gantry set up in a change from how I have framed up my engines.



Here's my copy of Parksy's cradle.



Bearings and webs in brass, the aluminum cradle is 2 in. wide.



And in Satin Black!



« Last Edit: April 18, 2018, 08:26:25 AM by Longboy »
Wadda you mean, "It don't run"???

Offline Longboy

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Longboy's "BEST FRIEND FOUR" block to cradle mount.
« Reply #2 on: March 29, 2017, 09:24:49 PM »
The crank cradle supported by a pair of slight S- bend raised cross bar stock. A set of motor mounts from aluminum angle are bolted to the block and join the bar stock legs using 3/8 in. rounds.



The block will get a set of .065 wall DOM cylinder liners of a 1 in. bore.
« Last Edit: April 18, 2018, 08:28:30 AM by Longboy »
Wadda you mean, "It don't run"???

Offline 90LX_Notch

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Re: Longboy's "BEST FRIEND FOUR" model gas engine.
« Reply #3 on: March 30, 2017, 12:26:28 AM »
Following along Longboy.

-Bob
Proud Member of MEM

My Engine Videos on YouTube-
http://www.youtube.com/user/Notch90usa/videos

Offline Longboy

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Longboy's "BEST FRIEND FOUR" block prep.
« Reply #4 on: March 30, 2017, 10:24:28 PM »
With a billet piece of aluminum for the block I get to use my new boring head on this project. I'll be using 1/4 in.width bar stock for the connecting rods here which allow me to reduce the bore centers to 1-1/2 in. This is a half inch less than my FOREMAN engine where I used longer webs and 3/8 in.width con rod stock.



I bore the cylinders with the block bottom upright in the mill to accept the liners at a finger press fit and overbore here .040-.050 about 1/4 in. deep for a film of epoxy to bond in the liner with the block to the correct position later when the combustion chamber is bored into the cyl. head. The epoxy at the bottom of the cylinder is far enough away from the combustion chamber where engine heat would not soften up the bond.

« Last Edit: April 18, 2018, 08:31:17 AM by Longboy »
Wadda you mean, "It don't run"???

Offline b.lindsey

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Re: Longboy's "BEST FRIEND FOUR" model gas engine.
« Reply #5 on: March 31, 2017, 12:02:22 AM »
Nice start, and should be a fun build. Do you have a sketch of where you are hoping to end up appearance wise?

Bill

Offline Steamer5

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Re: Longboy's "BEST FRIEND FOUR" model gas engine.
« Reply #6 on: March 31, 2017, 03:49:44 AM »
Hi,
 Ok pulled up my chair,  :popcorn: at the ready.
Nice work so far, keep it coming.

Cheers Kerrin
Get excited and make something!

Offline Longboy

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Re: Longboy's "BEST FRIEND FOUR" model gas engine.
« Reply #7 on: March 31, 2017, 04:54:53 AM »
Nice start, and should be a fun build. Do you have a sketch of where you are hoping to end up appearance wise?

Bill

Thanks Bill. No sketch-ups here. There will be some unique features that I haven't seen in models paging thru forums and Google images for BEST FRIEND though!

Dave
Wadda you mean, "It don't run"???

Offline Longboy

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Longboy's "BEST FRIEND FOUR" block prep.
« Reply #8 on: April 01, 2017, 01:03:17 AM »
The Chinese special boring bar makes a tapered groove around the cylinders for the O-rings that seal the cyl. head to block.




What looks like the beginnings of a water cooled engine was not to be. The mini mill doesn't allow a 6 inch long block to fit under a boring head for making the water jackets. BEST FRIEND will be air cooled!








Some finning can be machined into the side of the block for ambient heat rejection....but I will be using "cladding" instead. :o
« Last Edit: April 18, 2018, 08:38:48 AM by Longboy »
Wadda you mean, "It don't run"???

Offline Longboy

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Longboy's "BEST FRIEND FOUR" block prep.
« Reply #9 on: April 01, 2017, 11:59:20 PM »
Trying something different here. On Ebay, you can find heat sink material in various sizes. Always in hardware store grade aluminum, it is easy to cut and shape.



Choosing some 3-48 SS screws to bolt to the block, they can also be bonded in place.



There is room for another row between the motor mounts if needed. The same can be used for cooling cylinder heads. These are listed in mm. sizes, on BEST FRIEND they have seven 3/16 in. fins and are nominal 3/4 in. width.

« Last Edit: April 18, 2018, 08:42:22 AM by Longboy »
Wadda you mean, "It don't run"???

Offline Longboy

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Longboy's "BEST FRIEND FOUR" cylinder head.
« Reply #10 on: April 02, 2017, 05:59:13 PM »
The single piece cylinder head combustion chambers are bored 1/4 in. deep. The 10 mm. spark plug holes for CM-6 plugs are upright center.



Four head bolts per cylinder and intake/ exhaust cross flow porting drilled into head. Later the head will be decorated with some contouring /finning.



The liners are placed into block with their O-rings and then the head is mounted and torqued down. The liner bottoms out at the roof of head chamber and a reference mark is made where the liner is to be epoxied in the block with about .020 clearance from the chamber roof. Through the head porting, the liners are now through drilled into combustion chamber.



 :facepalm: A concern of mine is that the porting is drilled low in the combustion chamber just above the O-ring. Hot exhaust may penetrate the gap between liner and block deteriorating the seal then. The solution is to bridge the gap with a tube installed into the port through the liner if needed. On this test piece the liner is ground through to the hole so the cyl. head with tube protrusion can then be dropped down upon the block then. This can be done while still installed in the block.  :ThumbsUp:

« Last Edit: April 18, 2018, 08:46:42 AM by Longboy »
Wadda you mean, "It don't run"???

Offline Longboy

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Longboy's "BEST FRIEND FOUR" model gas engine.
« Reply #11 on: April 03, 2017, 06:10:01 PM »
The cradle, block and head pretty much completed, the body is there. Now ready for some internal organs to come and external appendages! :D

« Last Edit: April 18, 2018, 08:48:54 AM by Longboy »
Wadda you mean, "It don't run"???

Offline zeeprogrammer

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Re: Longboy's "BEST FRIEND FOUR" model gas engine.
« Reply #12 on: April 03, 2017, 11:13:17 PM »
Nice picture!

I'm not saying much but I'm following along.  :popcorn:
Carl (aka Zee) Will sometimes respond to 'hey' but never 'hey you'.
"To work. To work."
Zee-Another Thread Trasher.

Offline Roger B

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Re: Longboy's "BEST FRIEND FOUR" model gas engine.
« Reply #13 on: April 04, 2017, 06:37:01 PM »
Following along in the background  :ThumbsUp: :ThumbsUp:  :wine1: The use of commercial heatsinks is an interesting idea  :)
Best regards

Roger

Offline Longboy

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Longboy's "BEST FRIEND FOUR" ignition.
« Reply #14 on: April 04, 2017, 06:48:07 PM »
Points ignition working well for me and so equipped is BEST FRIEND. A change here to Kohler engine points. Brian Rupnow found these pushrod actuated points.....I'd thought I would try them out. Mounted to the front of the block they are crankshaft triggered.



The elephant faced brass piece is the pushrod guide. A tiny steel barrel sits on the rod against the points rub block and a brass barrel rides the points cam on crankshaft. The condenser ended up later under one of the screws on the end bearing block.




I find that the Kohler points has extraordinary stiff spring pressure for model engines. I radiused the flats on the points cam and sphered the bottom of the brass barrel for a softer ride over on the cam. Also with a needle nose pliers bent the spring to take some pressure off and it rides
well now. :ThumbsUp:
« Last Edit: April 18, 2018, 08:52:09 AM by Longboy »
Wadda you mean, "It don't run"???

 

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