Project Centaur

[redhouseluv]

Hi all

I would like to learn about ICE engines, specifically, carburation, ignition, timing, fuels and bought this old Westbury Centaur from an auction last year. It is not the prettiest engine, the flywheel and base are incorrect and she needs a lick of paint, but if I can get her going and learn about the items listed I have promised her a makeover.

I have bought a few bits and need some advice on some other bits which are missing before I can start; I am a little nervous of using fuels, electricity and sparks.

Ignition system
- I have sourced this from Minimag who advised on what I needed (see pic)
- I have been informed the Spark plug it came with is incorrect and have a smaller one
- I need to get the ignition to fire at TDC?
- You can get a nasty jolt from the ignition circuit?

Cooling system
- I need to rig up some sort of water supply to the jacket?
- Water goes in at the top and out of the bottom?
- These shouldn't be run without water as they will overheat quite quickly?

Fuel system
- I should use Colemans fuel I believe, but what sort?
- I was thinking about buying a RC airplane fuel tank (see pic).
- What sort of fuel line do I need to connect to the carb?
- Do I need to mix oil in with the fuel, if so what oil and how much?

Ventilation
- I assume that once fired up these give off some nasties, so should not to be run for a long time in a unventilated area

As you can see there's lots for me to understand and buy before I can make a start on this project, but I'm excited by the thought of seeing my first ICE engine come to life! I have other ICE engines in the 'backlog' so getting this going is a critical 1st step.

As always your knowledge and experience on all matters gratefully received 

[Jasonb]

Looks like the spark plug screws in so you could use that, just nee dto check th einternal length, out side does not really matter

Yes you can get a belt from the ignition.

Cool water goes in THE BOTTOM from the bottom of a cooling tank, warms and rises OUT THE TOP of teh engine and into the top of the tank.

Can be run for short periods without and water

Coleman fuel like this https://www.gooutdoors.co.uk/15893237/coleman-liquid-fuel-1-litre-15893237

I tend to use a R/C type plastic tank for testing but if you are going to put it on a base then something metal looks better. Original used the base as the tank.

Colemans seems OK with RC silicon tube though I would not leave any in the tubes long term but if you go with petrol then use Tygon (yellow) tube

I don't add oil but a drip or two of 2-stroke oil can be added but not a smuch a syou would use for a weed wacker or chainsaw

Open the shed door and windows

Would need to check if the carb is built for gas or liquid as I think there were options for both

Did you get the build article or drawings with it?

[Bear]

Nice find on the engine. Best wishes on your rebuild.

[redhouseluv]

Thanks, there's a lot of info to digest

I've got old copies of the drawings which are tatty and faded, but I have a the Centaur.pdf which is free to download from model engineer (see cover photo). This gives full build instructions

There is a reference in there which states it can run on either gas or liquid without any changes, however, given I have no experience of either I wouldn't know if it could or couldn't or how it should be set

I agree, fuel in the base will be better and will be the end state so for now I'll order a cheap R/C fuel tank and tubing to use with Colemans; I don't fancy the petrol smell everywhere

[redhouseluv]

I thought I'd make a start today with the ignition when I realised I had no plug cap! The ignition kit comes with a drawing to make a mini plug cap for the NGK CM-6 plug so made a start on that - quite fiddly and nearly forget to put the sheath on before soldering the HT lead to the internal spring.

I guess the next stage is to wire it up and and get a spark at TDC, I'm not quite sure how this Hall effect sensor is to be rigged up, but presumably somewhere along the camshaft where it triggers on a full rotation?

[michaelr]

On my Centaur I fitted a alloy disc with the magnet bonded into the disc face and held to the cam shaft by a grub screw, the Hall sensor is fixed to the lever that was for the original points ignition.
For timing I set the engine to TDC turn the disc on the cam shaft with the Hall sensor, and when the magnet passes the sensor the timing light flashes (That's the ignition point) tighten the grub screw, the ignition I used is the Minimag

[redhouseluv]

Thanks Michael, that's great info, thank you. I'm using the same Minimag ignition system.

[redhouseluv]

Started maker a hangar for the sensor, this needs to be a bit longer than the one used for the points to pass the over the the lobes where the contact breaker must have been located.

There's an interesting gap around the base of the inlet valve flange? The heavy flywheel looked like it was held on with the tiniest of Allen head bolts, but under a brass cap there's a proper keyway cut? I think there are many more mysteries to be revealed....

[Jasonb]

The gap is probably due to the tapered seating, the guide will have pulled up tight on the taper and there is still a way to go which is about right. If the flange hits the head before the taper is tight you will have a leak.

On the otherhand the key may not be tapered so the grub screw is there to stop the flywheel moving sideways while the key transfers the drive loads.

[redhouseluv]

The gap is probably due to the tapered seating, the guide will have pulled up tight on the taper and there is still a way to go which is about right. If the flange hits the head before the taper is tight you will have a leak.

On the otherhand the key may not be tapered so the grub screw is there to stop the flywheel moving sideways while the key transfers the drive loads.

- Ah okay, I didn't realise there is a taper; you are correct I had a quick scan of the drawings
- Understood re. the flywheel, I think if I can get this working I'd like to put an authentic flywheel back on. Casting is not cheap!

Question

How is the carb fed with fuel, is it gravity or other means? If the fuel tank is lower than the inlet (like in the base) what pushes the fuel into the carb. I'm buying a clear silicone tube so I can see if fuel is getting through, I'm assuming this should this be constantly full?

The trouble with buying part-machined or machined engines is that unless I put it together I don't quite understand how the whole thing works or whether components have been made correctly or not......let's see

[michaelr]

The fuel feed supply for the engine relies on the engines suction whether it's in the base tank or a remote external tank. if you have a external tank the top of your tank should be level with the needle valve on the carb, you don't want any gravity feed on the fuel supply as it will cause problems with flooding.
I used a external tank on my engine.

   

[Jasonb]

It is possible to include a non-return valve in the fuel line if the tank is below so that the fuel does not drain back into the tank. Should be less of a problem on this a sit is throttle governed than a Hit and Miss where the fuel can drain when it is missing

[Dave Otto]

From the drawing posted earlier it appears that the fuel flow is controlled by the lift valve. With no air flow the valve is on its seat and blocking the fuel port, when the air lifts the valve off the seat the port is opened and the fuel is able to flow. If the valve and seat are properly made you should be able gravity feed fuel to the mixer. This is the same way the Lunkenheimer mixers work on many early US built farm and marine engines.

Dave

[uuu]

But, if you mount the fuel tank higher, and rely on the lift valve, you should fit a cut off.  Just like on a motorbike, where the fuel tank needs a cut off, to prevent flooding if the carburettor float valve fails.

Wilf

[Jasonb]

Looked at the drawing and as Dave says the seat will act as a cut off as well as a non return, You may just need to prime the engine if the tank is below by putting your finger over the air intake and turning it over by hand which will lift the fuel up initially.

No float on the carb