Jason's engine

Introduction

As I came towards an end of the Minnie traction engine that you see in my avatar thoughts started to turn towards what to make next. Having done several stationary steam engines I felt like a bit of a change and the hit & miss type engines interested me more than aero engines though the Nemitt was tempting as this was currently being described in ME.

Edited By JasonB on 12/06/2011 12:54:33

How they work

Before going into the construction a few works on why these engines are called “Hit & Miss” may be in order. Unlike steam engines where the governor usually acts of a butterfly valve to control the amount of steam getting to the cylinder these engines are governed my making them miss part of the 4stroke cycle.

The governor weights activate a latch that holds the exhaust pushrod in the open position which means that there is no vacuum formed in the cylinder so no fuel/air is drawn in(miss). As the revs slow the latch will release the pushrod allowing fuel to be drawn into the combustion chamber and the sparkplug or ignitor will make the engine fire (hit) The inlet valve is usually just opened by the vacuum, there is no pushrod.

 

To be continued

I'm sure you jobbing engineers will just use whats laying on the floor but I prefer my work to look likethis 

Edit you read my mind Norman

Edited By JasonB on 12/06/2011 13:42:40

Slightly off topic but here is a video of a 'Hit & Miss' engine running Old Bessemer. Judging by the accents it is in the USA but still quite entertaining .

For those that have seen it apologies .

Edited By Martin W on 12/06/2011 23:46:45

Hi. Common and good engineering practice with the Standard Vanguard, the 8 and the 10. was that the studs had a small saw cut from the bottom up to the plain section, This was usually only done on the engine block, not the gear box holding studs.That did 2 things firstly it cleaned the threads going in and out, secondly it prevented hydraulic lockup, now a days its not done because of cost cutting, but with a Dremel and a diamond disc its easy to do studs for small models, it also saves fiddling with small drills, which in my case I invarabley break, I can also never get them to intersect properly. Dont ask me the problems we had getting studs out of the gearbox and starter motor when broken down in the bush, 80Ks from the nearest help, it always paid to take a full tool kit, but no room for gas or oxy. Lifes a bitch sometimes, but good experience and a laugh, later.

John Holloway

PS still cannot put smilies in posts