Longboy's "SILO" Model Engine!

[Longboy]

This image giving me and inspiration for a new model. ....exactly how far can you place those valves from the combustion chamber anyway?

The SILO engine build coming up soon!

 

[ZebDog]

Here we go again. I'm looking forward to this one

 

[Longboy]

The frame up for SILO is the same as four other models of mine. A short lower deck piece of alum. angle backside and a tall angle piece for the cylinders.

Out of the 4 inch angle stock, I do a ninety deg. mate of two quarter inch flats for the cylinders and bearing carriers.

The vertical member will have to be somewhat taller here.

Base support is 3/4 x 3/8 in. alum flats. Under these will be a pair of 3/4 x 1/2 in. CR steel bars mounted crossways to give some heft to absorb SILO's vibrations.

 

[Longboy]

The short deck gets one bearing carrier as #2 cylinder gets the shaft for the flywheel.

Upon this shaft goes the points cam and the MXL cam drive 20T sprocket. Between the bearing carrier and the sprocket here will be a brass eccentric to balance out the piston/rod assembly on the crank web. A change where previously a counter weight was secured to the back of the crank web using the geared set-up. I felt I would need more material mass to make the primary balance.

Topside, short deck gets the 40T sprocket and shaft for the cam drive. SILO is a twin cam engine! A transfer punch through the bearing and sprocket locates its position into the vertical cylinder frame piece for its second bearing support.

 

[Longboy]

Square tube steel butts up to the vertical with brass bushing and shaft. Picking up the drive with .5 Mod, 24T brass bevel gears.

Cam lobes slipped on shaft and somewhat centered with the cylinders topside. Top of tube trimmed away, A 6-32 socket head fastens the assemble to the deck and SILO has its exhaust set position ready for their valve blocks coming above.

Cam drive shaft continues through the vertical, supported with another long bass bushing to end for another set of the bevel gears.

A bearing carrier is bolted from the inside to the lower valve block plate for the intake cam shaft. Brass valve spring retainers are extra long. Drilled and threaded 6-32 after the spring, the valve stems are threaded to them. A 1/8 in. long set screw locks them to the stem and clears the cam lobe on rotation. Threading up/down on the valve stem varies the effective valve lift duration like a rocker and pushrod assembly.

 

[Longboy]

Tecumseh points set to the lower deck vertical. Convenient wire connection right at the frame edge.

The crank webs are low in the frame and the cylinder deck is high. Connecting rods end up longer and the reciprocating assembly is heavier then.

The brass counterweight on the flywheel shaft. 3/4 in. round offset 1/4 in. from centerline and drilled 5/16 in. to slip over shaft then. Two 8-32 set screws lock it to flats on the shaft and take care of the primary balance.

Over to #1 cylinder , the stub shaft is 5/16 in. , turned down for 1/4-28 thread and 3/16. in. The items in view are spacer, spring washer, threaded counterweight, lock nut and the 2:1 brass gear drive pair for distributor topside of deck.

And in the shop.....sum guy with that look of "sometimes seems to know what the hell he's doing here"!

 

[Longboy]

The black diagonal object is a frame brace. Two flats bolted together will flex more than real angle pieces and the horizontal component with the cylinders firing off shoots the stabilities away. Mounted between the cylinders....even this brace was not enough to quell the diving board action seen once up and running. You can't beat a four corner box mount, so SILO has a pair of round stock posts at its front corners. That ended the flex issue.

A block of Delrin and my home developed fuel mixer meters the fuel feed to the valve block.

I spent a couple days working a vapor feed to SILO. I like the novelty and simplicity of these....but couldn't make it work well enough here. The fuel level in the tank has to be constant or you fiddle with the valve feed endlessly. They seem to work better using a jar instead of a tube and for single cyl. engines. Save for another application someday.

 

[Longboy]

The tough part on the build was bring up the connection from the valve blocks into the cyl. heads. Just not going to come straight up and curve into the front and back of the heads.

I had a couple of these 1/8 in brass compression fittings in a tray. Re-drilled them for 5/32 in. tubing, the nuts are 5/16 -24 and the other end is resized for 1/4-28. Washer and O- ring to the valve blocks and O-ring to the tube under nut to make the air tight seal. SILO needs 10 of these @ $3.79 each. I made my own with 3/8 brass hex and partied on to Burger King for a couple of lunches on the savings!

My tube bender has a 5/16 in. radius and with the single port into heads at the side, even with the stiff brass tubing I could make the bends needed and get them into the fittings.

After a couple of throw away samples, I managed to get the four tubes pretty symmetrical in the fit. K&S Metals does have 5/32 in. tubing in more malleable copper.....so I did have an alternative if needing a tighter radius bend by hand for SILO.

 

[Longboy]

Cylinder heads same diameter as cylinders. Just a sparkplug on top and the profile presented is somewhat of a silo with filling chutes.

For those who have not seen the business side of geared together crank webs.

To vary the gear lash to prevent binding or clatter in operation, one of the bearing carrier mounting holes in the vertical frame member should be oversized a few thousands and the screw holes on the carrier's flange oversized so you can shift the crank web slightly in/out its counterpart on the other shaft for the mesh.

My ideal size for flywheels in this scale are 3.75-4 inch dia. / .750- 1 inch long. Preferred material is 12L14 steel or brass. Fits on the mini lathe and does take 2- 3 hours of cuts to fashion. I can sneak my models to under a thousand RPM then!

You fellow modelers enjoy the Easter, Pass Over holiday now! SILO's presentation coming this week sometime! ----- Dave.

 

[Longboy]

WELCOME TO LONGBOY'S PREMIER OF THE SILO MODEL GAS ENGINE!

SILO turned out pretty good for me. Only thing new in design was the placement of the valve blocks adjacent to the cylinder deck and their plumbing routes up to the heads.

SILO was started the 1st week of Febuary.

And completed the last week of March.

Bore and Stroke: 1x1-1/8 inch.

Free air cooling. Will idle 800-900 RPM range.

A milestone year for me! Ten years of wildcatting I/C designs after the plan built Webster. (15 gas engines) I'll have to go to Home Depot and get one more shelf board and brackets to add to the wall for display now! ☺ SUMMER BREAK IS HERE! Happy Modeling to you!

Enjoy the video! LONGBOY ENGINE, Dave.

 

[ZebDog]

Congrats on another wonderful engine. I always enjoy seeing these beautiful creations come to life.

Steve.

 

[a41capt]

Wow Dave, you’re not only creative, but extremely fast in your builds! I’m struggling along attempting to build Rudy’s Pioneer Engine and aren’t even half way done after a month and a half.

Another beautiful runner, congratulations!!!
John W

 

[xander janssen]

Impressive distance between yhe valves and cylinder.

 

[Longboy]

Wow Dave, you’re not only creative, but extremely fast in your builds! I’m struggling along attempting to build Rudy’s Pioneer Engine and aren’t even half way done after a month and a half.

Another beautiful runner, congratulations!!!
John W

I would say you are pretty much on target time wise on your Pioneer. You will find a couple weeks in there that parts made went quicker than you thought they would! I spend 1-5 hours daily. Some of that time is thinking ahead a couple steps and just sitting at the bench before cutting up stock. Many parts, like pistons, rods, valves and guides, radiator fining, rocker arms are repeats from earlier builds and quick in manufacture. You will find your style John.

 

[a41capt]

I would say you are pretty much on target time wise on your Pioneer. You will find a couple weeks in there that parts made went quicker than you thought they would! I spend 1-5 hours daily. Some of that time is thinking ahead a couple steps and just sitting at the bench before cutting up stock. Many parts, like pistons, rods, valves and guides, radiator fining, rocker arms are repeats from earlier builds and quick in manufacture. You will find your style John.

I’m making my own mods to “improve” a design as I go along. Obviously gonna stick with the operating premises associated with the non-compression principle and much of the design, but looking at some shortcomings, I’m looking for improvement as I go along.

thanks for the encouragement!

 

[xander janssen]

I have some question that came up when thinking about my new to be designed engine and your engine.

What compression ratio do you have in this engine? It seems to run pretty stable and relative low RPM.

Did you correct the volume of the combustion chamber for the volume of the long tubes between the cylinder and the valves?

 

[Longboy]

Thanks Xander. No need for considering the added volume of the tubes to the combustion chamber volumes. The brass tubes are 5/32in O.D. and the length per cylinder is approx. 6 inches. (3 in. each tube). The formula for tube volume comes in at around 1.3cc/ cyl. for the tubes substracting the wall thickness of tube. My compression ratios are under 4:1 for easy, no kickback hand starts though the hand grip to a 4 inch flywheel is pretty wide. The cordless drill the way to go for start ups.

 

[minh-thanh]

Hi Longboy !​

My compression ratios are under 4:1 for easy,

I have a question :
I'm planning to change the compression ratio in one of my engines to 4 - 1 for testing, what I'm wondering is: with a little loss of compression air beween cylinder + piston + rings - Maybe the actual compression ratio is only 3.5 - 1 or 3 - 1 - is enough to guarantee the engine will run ?
Thanks !

 

[Longboy]

Our low performance engines will run fine. A single cylinder engine the best test bed to play around with combustion pressures. I find that a higher compression just makes the engine too hard to hand start and is harder on the engine overcoming the up strokes. It better be clamped down to a table. You can get some nasty kick back if the ign. timing too far advanced. Dropping another point in C.R. most likely will give the engine a more relaxed environment for easy idles. I believe there is a no compression four stroke model out there from years ago. Give it a Google search or another hobbyist can make reference to.