Longboy's "OVERTIME" I/C Twin!

[Longboy]

About 3 yrs. since I built my first I/C twin engine. My "GEMINI" is a good start but I want another crack at an inline twin to address a couple of shortcomings in its build. Can I make improvements in servicing, durability and a new feature using basic machine shop know how and NO PLANS in the same scale? ....The story of "OVERTIME" starts this weekend!

[Longboy]

  With this engine being an open crank style, a 4 piece frame is the backbone of Overtime. Two end plates, a deck plate and base plate. The deck is overlapped to the endplates and the endplates are overlapped to the base. Eight, 6-32 socketheads holds it together. For servicing you can remove the deck with all top side components as a unit and either end plate for access and removal of the crankshaft.  A couple of brass bearing holders for each end plate will be the crankshaft support. I'll be using Oilite bushings here, 3/4 inch long ( 1/2 in. shown). More bearing area than a set of roller bearings that also will work fine, just builders choice here!

[stevehuckss396]

Interesting!  Wondering, how is the rotating assembly lubricated? Do you just put a few drops of oil in places before a run?

[Longboy]

Hasn't been necessary....yet! Oilite bushings are self lubed, impregnated with 30W. Initial first runs a couple drops of WD40. I'll see how it goes after more run time.   http://en.wikipedia.org/wiki/Oilite

[Longboy]

A brass flywheel is secured to the crankshaft with a taper collet made from Delrin. A 3 screw retainer makes the press fit or actually draws the flywheel back into the collet. This 1st collet was too short, didn't get the grip and a longer one was made without the split and tried out...the right length worked out better! The Delrin seems to compress enough without having the split down the side. 

[crueby]

Is the hole in the flywheel tapered same as delrin as well? Neat way to do it.

[Longboy]

Yes crueby....it has to be a matching taper inside the flywheel hub.

[Longboy]

A fabricated 5 piece crank starts with 12L14 steel web material. A generous length of each web 5/8in. long for heft and support of a 5/16in main shaft and 1/4in throw pin of stainless round stock. Drilled and reamed as one piece then parted to length.

[Roger B]

Good start on the "Overtime"     I will be following along   

[Longboy]

The webs are internally balanced to the piston/rod assembly. Two half inch through holes at 5/8 inch yields a hair under 1 oz. of removed material.

[tvoght]

I'm watching and enjoying your build. Your Delrin tapered collet gave me an idea at the precise moment I needed one!

--Tim

[Longboy]

Good Tim, something I presented here helped you.     Dave.

[Longboy]

The shaft is joined to the web by press fit. A straight knurl gets the bite into the web. Some cold bonding agent, either thread locker or Epoxy, supplements the primary grip of the knurl when driven in. After pressing, the assembly is chucked in the lathe. The shaft is paralleled to the web with some light taps and the assembly is then set aside and repeated for the other end.

[Graham G]

  Yup i'm in for the ride, I like what I see so far
cheers
Graham

[Longboy]

The weak link in a 360 Deg. crankshaft for a two bearing inline twin is the throw pin. Its long and narrow and joins the heaviest parts of the crank. I used 1/4in. stainless round here, upsized from my GEMINI engine.



The pin is locked to the web with a 10-32 set screw instead of being pined or silver soldered to the web. The pin has to be removable as I am using roller bearings on the rods.