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Author Topic: Davies Charlton engine  (Read 594 times)
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whiskers
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« on: February 20, 2019, 11:36:36 AM »

Hi guys,

Just received through the post a DC engine I won for peanuts on a certain auction website. It was listed as a "0.75cc in good condition which turns smoothly with good compression" or similar...

Ah I thought, a Merlin! Just the thing for a bit of classic free flight.

As I said, the engine arrived today and was seized solid with varnish. I have stripped it down and cleaned it up and it now turns over and 'plops' nicely over compression. Good, I think it will run OK.

Question is is it a 0.75cc Merlin? It seems a bit big for a .75cc to me. The cylinder head is 2.5cm in diameter by about 15mm tall with five fins. It is red - but this means nowt cos they did various colours I think. I measured the piston with my calipers and it was 0.519" or  13.2mm. I'm thinking it's a 1.5cc Sabre. Obviously I need to find out for prop' and model size!!

Can anybody shed any light on this?
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billdennis747
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« Reply #1 on: February 20, 2019, 12:07:20 PM »

It sounds like a Sabre. You know the piston diameter - estimate the stroke and do the cylinder sum, which I knew in 1969; something about pies. I just googled Sabres and the cylinders were red, as were Super Merlins.
« Last Edit: February 20, 2019, 12:44:36 PM by billdennis747 » Logged
whiskers
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« Reply #2 on: February 20, 2019, 12:59:49 PM »

Thanks Bill I never thought of that!!. I didn't want to pull the whole thing down again so I Just took the back off again and estimated the stroke at about 1/2". On a CC calculator I found on the web that gives me 1.733cc. I guess it's a Sabre then.
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Squirrelnet
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« Reply #3 on: February 20, 2019, 02:53:37 PM »

Yep sounds right to me too

And just to check here's an add from 1957 to confirm. It gives prop sizes too but I think you could put a 9" x 4" on it for sport flying

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Re: Davies Charlton engine
« Last Edit: February 20, 2019, 03:12:14 PM by Squirrelnet » Logged
whiskers
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« Reply #4 on: February 20, 2019, 03:11:56 PM »

That's confirmed it then. Has to be a Sabre.

Not having played with Diesels for ages how do establish a compression setting for initial start-up without running the risk of it being over-compressed? There is little difference in feel between what seems like quite large adjustments of the comp' screw.
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Squirrelnet
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« Reply #5 on: February 20, 2019, 03:24:54 PM »

Its a bit of feel thing. Probably the easiest is to set the needle valve at 1.5 - 2 turns open.

Set the compression so that it produces a nice sounding plop as you described and start flicking it over gradually increasing the compression as you do, maybe giving a couple of flicks at each setting until it starts to fire. Once it shows signs of life its easier to gauge where you are.

If you start soft and gradually increase it should fire before it gets over compressed.

The range between just firing and full compression is about half a turn I think. Originally they had a little pin installed so the compression lever stays within the range of 1 turn but they have seldom survived more than one instance of flooding the engine.

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billdennis747
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« Reply #6 on: February 20, 2019, 03:46:50 PM »

Good advice. I would add that it is important to avoid flooding because you won't know where you are. Choke it until the fuel reaches the needle valve then stop. Close the exhaust ports with the piston and squirt fuel onto the piston - not into the open ports or the intake.
After that, it's all in a good hard flick.
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whiskers
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« Reply #7 on: February 20, 2019, 04:25:53 PM »

Starting to remember some of this stuff now. Thanks for the advice. My first ever engine was a Sabre and I remember that (and all the other DC's I've had over the years) have all had the compression lever guarding pin thingy. This motor hasn't got the pin and there is no threaded hole to receive it. I guess this means something, like maybe it's an early one. It has 'made in England' on the crankcase...but the later ones were made in the Isle of Man?!?

I'm away on my canal boat for a few days now so starting fun and games will have to wait a week or so.
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kkphantom
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« Reply #8 on: February 20, 2019, 07:14:54 PM »

Off topic slightly but we've sold up in Australia and are buying a liveaboard narrowboat around May-ish. See you on the cut!
Gary
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whiskers
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« Reply #9 on: February 21, 2019, 02:19:14 AM »

You'll love it! Are you going to be continuous cruisers or are you having a 'base'?
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John Webster
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« Reply #10 on: February 21, 2019, 02:57:48 AM »

I have a mental picture of whiskers and kkphantom flying Rise Off Water models in a turning basin.
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« Reply #11 on: February 21, 2019, 03:30:24 AM »

Continuous cruisers, yeah, we could sit in a kayak and fly controlline!
Gary
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lincoln
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« Reply #12 on: February 21, 2019, 09:47:49 AM »

Seems like a coracle would be better. ;-)
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Starduster
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« Reply #13 on: February 21, 2019, 10:32:00 AM »

Continuous cruisers, yeah, we could sit in a kayak and fly controlline!
Gary

There's an interesting Physics question:

What would happen if you tried to fly a control line airplane while seated in a un-anchored boat/

My guess is that the centripetal force would make the boat describe an ever-widening spiral.
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kkphantom
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« Reply #14 on: February 21, 2019, 07:24:25 PM »

Probably easier to wear waders and stand up, most canals are only three feet or so deep.
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whiskers
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« Reply #15 on: February 22, 2019, 03:30:43 AM »

kayak combat perhaps? Or ,what are the teams thoughts on prop' size for the lusty Sabre to power a 15 ton Narrowboat? I've had to put my boating on hold for a while due to various reasons so attempted start-up may come sooner than I thought. Thanks for all the input guys.
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whiskers
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« Reply #16 on: February 24, 2019, 11:33:16 AM »

Well, I attempted to run the Sabre this afternoon.

I fitted an 8x4 Master Airscrew and used a freshly opened can of Model Technics D1000. I flicked away, gradually increasing compression until I was rewarded with a couple of 'crackles' then I got serious with it trying various compressions (within 1/2 a turn or so each way of the setting that gave the life) and varying levels of choke/flooding/needle setting. Must have spent an hour on it and have only been rewarded with a few very short runs. And it really is a female dog to start. When started it seems to 'burp' like a Sopwith Camel coming into land. It will then settle a little and increase revs if the compression is slightly upped, then, when on song it starts to sound hard' and dies.

Maybe it's not a good one? My longest run so far is about 10-15 seconds. I have now gashed my trigger finger on the prop so that's it for a day or so!!!

Any ideas fellas?
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Squirrelnet
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« Reply #17 on: February 27, 2019, 03:40:13 AM »

Quote
if the compression is slightly upped, then, when on song it starts to sound hard' and dies

That sounds like over compression.

I would sort the NVA out and go from there
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fred
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« Reply #18 on: March 02, 2019, 12:38:27 PM »

A bit of Rubber hose shield on one's prop flipping finger is IMO: Mandatory with diesels.
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applehoney
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« Reply #19 on: March 02, 2019, 01:48:44 PM »

Rubber hose ?    Have been running diesels and glows for nearly 70 years without such protection ... you'd lose the 'feel' of the engine.   
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OZPAF
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« Reply #20 on: March 02, 2019, 06:37:19 PM »

This may sound strange - but is this motor actually run in? It sounds like it may be overheating which would have the same effects as over compressing.

I would do a number of runs just past or even on the "burping" setting. Don't over choke it - just draw the fuel to the carby and then prime through the exhaust valve onto the side of the piston.

How does the compression feel?

John
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Squirrelnet
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« Reply #21 on: March 03, 2019, 03:39:55 AM »

Thought It worth pointing out that there's some crossover in this thread with another one started in the power FF section.

http://www.hippocketaeronautics.com/hpa_forum/index.php?topic=24091.0

From Whiskers

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Re: DC engine woes
« Reply #15 on: March 01, 2019, 05:16:47 PM »


Made a tank out of one of my dogs pain relief syringes - like the ones I used years ago on my free-flighters. Engine seemed like it wanted to go a couple of times then screamed into life and...kept running!!! Ran out a tankful and started up again after a fill and ran out another tankful, then another.

I guess I'll call that fixed then. It runs best with between 1/2 - 3/4 turn out on the needle so I guess the motor must have been well too rich even with the needle fully seated prior to my mods!!

Thanks everyone.
.
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OZPAF
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« Reply #22 on: March 03, 2019, 05:26:26 PM »

Thanks Chris - the man has solved his problem.

Good luck with your Wilga on that lovely Port Meadow field.

John
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