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LONGBOY'S "WEDGE RUNNER" Model Gas Engine.

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Longboy

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Build season came early for me this year in August as the virus changed my routine and I needed some around the house activities to come into play long before the cooler weather comes for my usual involvement time with modeling.
So I begin with a concept.

I've taken one of these and put it into the Longboy Engine smelter......


........then I added one of these into the smelter.


Then I started to pour the combination into the mold of the mind! The WEDGE RUNNER STORY coming this weekend!
 

Longboy

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This parallel twin starts out with a 3x3x.25 in. angle aluminum. Bored for a pair of DOM liners for 1in. bore pistons.


Aluminum rounds for air cooled radiators on the top side deck. The bore center line is at 2 in.


A pair of 4-40 screws hold the radiators to the deck. This is a change from a 3 screw set up I use releasing the top of engine from the deck for reasons explained later. At a right angle to the crankshaft I can get the screw driver between the crank webs to remove the screws.
 

Longboy

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The cylinder head will be my hybrid flat head design effort.



I bore the combustion chambers to around .375in. depth. With the flat top pistons rising to a point about .250in. below the deck height, I get the right compression for the chamber volume presented.

From the head perimeter port into the combustion chamber. The valves are not in the combustion chamber but in a remote assembly attached to the head at the port.

 

Longboy

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The head is milled out around the ports to dock the valve blocks.





And the head is ready for the valves. Looks good!



 

Longboy

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Valve blocks made from .250 in. flat stock, 1 x 1.25 in.



An O-ring seals the valve between the two blocks. Mounted to the head, a brass tube with o-ring seals the valve port to cyl. head port.



 

Willyb

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Looking good Longboy. Will be following along as you build this engine.
Cheers
Willy
 

Longboy

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The valve blocks bolted to the head determine the camshaft height above head. These cam towers came in from the valvetrain division with the shafts! Lobes ride on the bucket valve spring retainers threaded onto the valve stem.



Those towers look pretty high to the top of the cylinder head using 3/4 inch tall stock for the head.



I will raise the height of the head by making an overlay using 3/8 in. stock for a better proportioned view.
 

Steamchick

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The valve blocks bolted to the head determine the camshaft height above head. These cam towers came in from the valvetrain division with the shafts! Lobes ride on the bucket valve spring retainers threaded onto the valve stem.



Those towers look pretty high to the top of the cylinder head using 3/4 inch tall stock for the head.



I will raise the height of the head by making an overlay using 3/8 in. stock for a better proportioned view.
I would advocate installing a centre bearing for each camshaft.... Just looks wrong (to me) as it is. Also you may need hardened steel cam followers, and a very good oil supply to avoid excessive friction and wear of cam followers. Case harden a polish the cams.
K2.
 

Steamchick

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Build season came early for me this year in August as the virus changed my routine and I needed some around the house activities to come into play long before the cooler weather comes for my usual involvement time with modeling.
So I begin with a concept.

I've taken one of these and put it into the Longboy Engine smelter......


........then I added one of these into the smelter.


Then I started to pour the combination into the mold of the mind! The WEDGE RUNNER STORY coming this weekend!
That Gilera is just gorgeous! Guess it's a real one, not a model.
K2
 

Steamchick

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Did you remember that compression ratio must include volume of ports right up t the valves, plus internal volume of the space inside the spark plug, as well as the chamber at the end of the cylinder at tdc?
I guess you did... just checking.
K2
 

awake

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K2, Dave has built several engines using a similar head and valve design ... very interesting and unusual engines, which run very well.
 

Longboy

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Did you remember that compression ratio must include volume of ports right up t the valves, plus internal volume of the space inside the spark plug, as well as the chamber at the end of the cylinder at tdc?
I guess you did... just checking.
K2
Ah no K2. This engine doesn't seem to care that the battery in my calculator went dead before I got to these considerations. ---Dave.
 
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Willyb

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If you used rocker arms you could lower the camshafts and put them between the intake and exhaust valves. That would lower the height of the engine. Just a thought.
 

Longboy

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I would advocate installing a centre bearing for each camshaft.... Just looks wrong (to me) as it is. Also you may need hardened steel cam followers, and a very good oil supply to avoid excessive friction and wear of cam followers. Case harden a polish the cams.
K2.
Thanks K2. Center bearing here not mechanically required. Bearing to bearing distance is 4 inches. Don't need harden lobes for a low RPM engine with valve springs of .022 wire. Axle grease on the lobes the right lube here.
 

Longboy

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If you used rocker arms you could lower the camshafts and put them between the intake and exhaust valves. That would lower the height of the engine. Just a thought.
That is true Willyb. Seems that in these days of modern OHC engines prevalence, the heads are taller than the block. I am sure most will like the look and proportions of WEDGE RUNNER as the postings continue. ---Dave.
 
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Steamchick

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Thanks K2. Center bearing here not mechanically required. Bearing to bearing distance is 4 inches. Don't need harden lobes for a low RPM engine with valve springs of .022 wire. Axle grease on the lobes the right lube here.
Axle grease (for CV or UJs) contains Molybdenum. The best anti-scuff readily available. Good.
K2
 

Longboy

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The holes in the overlay are over sized so the head can be removed with the overlay attached or not. Head bolts and spark plugs pass through.



A pattern of cooling fins milled in.





Three socket head 4-40 screws right down the middle secure the overlay to the head then.



And the cam towers shortened up nicely!

 

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