Hi guys,
With the base and parts for the Corliss engine awaiting painting I thought I’d have some time on a couple of diesels that have been on the cards for rather too long. Though some parts of this project have already been made this won’t be a build log as such - the Throp will take precedence - but will be more on an ‘as and when’ basis. I would like to think however that I would have them finished for running at the Forncett ‘do’ in October.
Perhaps first however a little bit of background is in order….
The ED (Electronic Developments) 3.46 cc 'Hunter' has long been a 'favourite' engine. This one, still with original box, was recently passed to me as a gift from the original purchaser by my long time control line model flying friend John Leonard.
I think I said somewhere else it hadn’t been run for forty years. John assures me it hasn’t been run since just after purchase in the mid 1950’s. Despite the dirty appearance it certainly doesn’t look as if it’s had much running though I notice it has a replacement screw at some stage. The nice thing though is it has an original needle and spray bar which can be copied.
Until this example then I had only owned an original one for a very short period when I was around 14-15 years old. I had bought it second hand and built a KeilKraft Pacer control line team racer to fit it into. Anyone remember this ad?
On it's initial outing I had had several nice flights before clipping the prop (engine was stopped) on landing. Nothing was thought about this until starting it for the next flight - that clip had broken the crankcase all around the front bearing housing where the wall section was very thin due to the bearing housing behind. I replaced the ‘case but like so many engines over the years it disappeared, no doubt to fund purchase of another engine.
A couple of years ago John (L) asked me if I could have a look at his version, which was binding on bottom dead centre. A strip down revealed nothing more than many years of languishing castor oil crud that had gone rock hard and the con-rod was hitting this as it passed. Scraped off and cleaned with solvent it was back to running state in very quick order.
The Hunter - in it's day - was (to a young teenager) a big engine and had a reputation of being a finger grabber - a reputation well deserved I should add
and this proved just the same but having never used anything but the digits to start an engine why change the habit of a lifetime
The crackle of the exhaust in the workshop door soon had ideas of getting one for myself just for nostalgia sake but as it sat on the bench waiting for JL to pick it up I became to realise just how much I actually liked it's shape. The thought of a 5cc version didn't take long to manifest itself and a quick check of the small increase in dimensions required showed that it was significant enough to have a visual difference.
A GA was laid out and a preliminary set of drawings done ….
…… and the usual start made to hack out a crankcase from ali block. There would be a couple of challenges - particularly around the bosses where the backplate screwed to. Unfortunately at around this time my interest was distracted elsewhere (as it does
) and the roughed out rectangular blocks albeit with the internal dimensions finish machined and the bronze bush installed were popped in a box and gradually forgotten.
Sometime last year I had need to turn something non modelling orientated from ali and the thought occurred to ‘just’ turn the outer front ends. All the old buzz quickly returned and again in quite a short time I had not just two crankcases but the backplates and venturi’s too. Despite a serious ‘plastic distraction’ at the time this was the catalyst for the resurgence of interest in machining and the desire to do something about those languishing Throp engine parts. Unfortunately no images of machining the crankcase parts were taken but it was machined from solid much as the ETA and Atomatic engines described previously on here.
The cases were easy enough to machine – as said, only the bosses where the backplate screws to presenting a small challenge but once done there they have sat waiting along with material cut off for the cylinders and crankshafts.
I guess some you will remember this classic old British design with a firm degree of nostalgia and hopefully, on that note, will be of interest.
I’ve been turning the cylinder heads this morning and so far the ‘cases, cylinders and crankshafts have been machined. There’s a definite whiff of ether in the air
Regards - Tug