LONGBOY'S "JUSTABLE" MODEL ENGINE.

[Longboy]

I got a phone call last month from "Bob Thomson" over at "NOR'WESTERN LOGISTICS"' They are a maintenance and infrastructure support company for the mining, lumber and oil industries and service U.S. and Canadian firms. He tells me that the little single, "Sentinel" engine I developed for them in 2010 was just ideal for their purposes. Durability, low service intervals and all weather performance. Asked if I would be interested in creating another with a greater capacity. Since I was wrapping up my build of the "Side Shafter" engine........I could most likely have a presentation built before Labor Day.

Starting soon, The Longboy "Justable" engine!

SENTINEL ENGINE (2010)

[Admiral_dk]

Happy customers are always nice and that they ten years later ask for a new design from you is a very good tribute 

But I can't get my head around, a open crank engine with no lubrication system, being a low maintanace power plant ...?... what is it used for / what kind of work is it performing for them ?

Best wishes

Per

[Longboy]

Thanks Admiral. If you are not changing oil periodically.....that kinda makes for low maintenance. JUSTABLE is a model and not used by the business per se.     

[Longboy]

The beginnings of JUSTABLE start with these two pieces. The 2 inch bore centerline cylinder head is a leftover from my first 2 cyl. engine, "GEMINI". I couldn't get a center bearing to work by getting a proper line up of 3 bearings at the time. I duplicated a shorter cylinder head with 1.5 in bore centers and reworked a 2 bearing crankshaft and let a single long throw pin carry both con rods for that engine. Now I can use spare parts on a current project.



On this head, the outboard holes for the head bolts are at 3.75 in. centers. The angle aluminum, left over from SIDE SHAFTER just completed, is 4 in. ! Now I can use this head on a project! With some .25 in. stanchions to mount the head to the deck, I have....." just enough room".....to mate these items and save a few days making another head! Karma shines for my good!   

[Longboy]

JUSTABLE gets a three piece set of crankshaft webs.





And the finished segments. There is one throw pin.....but three webs! Are these enough for a twin or am I short a piece?  I'll let the forum play around with that question before the next posting.........

[Longboy]

I'm trying out a hole saw on the deck for the cylinders, my original method before I bought a boring bar kit for the mill. Slow going with lube, the mini mill breaks circuit often if too much feed on one inch dia. and greater tools. Finished up with a basic China Special bore tool.





Barrel shape pistons with multi piece con rods tuck into the bores. Note the difference in the rod big ends between the two.



The camera's view alludes to a pair of over sized radiators upon the cylinder deck..... however they fit within the deck perimeter to bolt on the cyl. head. I had......"just enough room" to make it so!   

[Longboy]

Underneath the short angle frame piece goes the Tecumseh points. My favorite for their versatility mounting in tight quarters. The crankshaft offset from center of piece leaves little room on the outboard side to place them. Well.....I was "just able" to do such as you see. The Phillips head will be replaced with a 4-40 socket head to adjust the gap easily with a ball end Allen wrench when assembled.



A sample crankshaft stub with the points cam trigger through the bearing gives me an idea where the pivot point will be when the cam hits the rub block.



The spring and stud insulator stick out from the frame. The insulator will slot into a thin piece of hardware store angle aluminum and will make for easy connection with the ign.coil. That bracket will bolt up to the backside of frame tucked next to the bearing carrier.



One other component goes onto the crankshaft here, the cam drive. GOLLY! ...it "just made it"!   

[Longboy]

I'm trying out and sticking with a new material for the valves.



From SPEEDY METALS with a full line of diameters of 12L14 steel rounds. Ordered some valve material as well as flywheel rounds at 3.75 and 4.0 inch dia. I'd say an easier cut than SS. No galling or chunking and a clean finish with no follow up treatment in the seat area of valve.





As for flywheels. Still a chore. Slow going removing metal from large diameter stock on the mini lathe. 

[Longboy]

The lower deck piece is a  2 x 2.25 in. surface. I need two items upon it, the cam drive and a distributor.



The cam sprocket location is the difficulty here.   



I measure for an approximate position for the camshaft bushing through the vertical leg of the cylinder deck, go to my belt length calculator (https://www.bbman.com/belt-length-calculator/ ) and order a MLX 81 tooth. The arc in the upper left corner is my margin of position to drill for shaft. It is a 2 inch center line, crank to camshaft.
If the belt is low to the left......I am running the lifters too close to the edge, right off the upper deck and with the belt upon its sprocket, the belt slot will be beyond the left edge of lower deck.
If I follow the arc up and to the right, I'm running the cam lobes right into the underside of the upper deck. Had to sit and think about this for awhile........and I got a solution!   

[Longboy]

The best way was to pull back from the 2 inch crank to camshaft centerline. Lower and to the right, under where I want the lifters to be.



Belt slot will end before running off the deck edge and if too much slack in the belt, can reorder. Most likely a MXL78 tooth.

Trying an idler to take up the slack now and it will work fine with the 81T belt.    Locate with a couple of transfer punches and drill the frame for the shafts.





One caveat with the chosen location of cam sprocket is its flange sits right on top of the short deck now. With a slitting saw, I milled a shallow trough in front of the sprocket to the end of the deck for the clearance. Trimming the flange back about .025 in. would have done the same..... but I was looking for adventure with the slitting saw! 

Still going to be tight under the lifters. So I re-bush the cam sprocket for a 1/8 in. shaft now. These cam lobes start form 5/16 in. 12L14 round stock secured with 4-40 set screws to their shaft.

[Longboy]

Back on the other side, I shorten the lifter guides to be flush with the cylinder deck underside and cut back the lifter heads so they have some space between the lobes and guides. Of course....I just made it! 



JUSTABLE's distributor sits on the back corner of the short deck. Its bracket is a piece of the angle aluminum milled for the correct mounting angle along the apex.



With the camshaft revised at 1/8 inch through the brass bushing to end of sprocket, I need a 3/16 in. shaft for these 20T .5 mod gears. They come holed at 3-4mm and I re drill for this size shafting. An inch long piece is drilled the eighth inch and pressed fit over the cam shaft with some epoxy. There is a flat for the set screw under the gears.



These gears are tiny and on an eighth in. dia camshaft.......to prevent flexing and going outta mesh screwing up the ign. timing, an R166 bearing supports the tail end.



Now if you look closely! (  not again Longboy). Oh yes.......the distributor gear........"just fits" between the sprocket bushing and drive gear! (ah- huh  )

[Longboy]

Can an overhung crankshaft be developed for a 360 degree two cylinder inline engine? Perhaps best described has a hybrid as one crank throw supported in two webs, and the other crank throw.....not supported by two webs. What does that look like?

A third crank bearing is mounted under the deck between the cylinders. With two bearings in the vertical portions of frame, a transfer punch is inserted.



The bearing block is 1/2 x 1 inch stock. A bearing cap bolted to its bottom, the butt joint is slightly below the crank center line, then shortened up to the correct match up with the point on the transfer punch.



There is an Oilite bushing slipped over the shaft segment for this bearing block. The crank webs are assembled onto the shaft segments for the rotating assembly. The front two webs are pressed fit to the shaft with the Oilite bushing with two thin SS washers properly spaced for some slight thrust movement and capped in the lead bearing block.



The bearing block shank will be reduced substantially as it is obviously too meaty in appearance here. The illusion presented upon completion is that JUSTABLE's crankshaft appears to be hanging out in space under its cylinders, a floating crankshaft projected out from one end.

[crueby]

Thats a neat look for the crankshaft!

 

[Longboy]

Working on the under framing. This set up not giving me enough clearance for the flywheel.



Going with a couple of skid members and transverse bars with the rubber feet.



Just a little more time to go here.........and then it looks like it is finished! 







COMING SOON!    The LONGBOY "JUSTABLE" MODEL ENGINE!     

[Longboy]

Welcome to Longboy's "JUSTABLE" engine presentation!



An inline 360 twin. 1x1 inch bore & stroke.



Work began on JUSTABLE 1st week of March.



And completed 2nd week of April (5 weeks)



Special features!



Cantilever frame construction.

A floating crankshaft.















Thanks for following! Dave.     



<a href="https://www.youtube.com/watch?v=oWDvMdwQkEQ" target="_blank">http://www.youtube.com/watch?v=oWDvMdwQkEQ</a>