Suitable fuel for boll aero engine

[half whitParticipant @half-whit]

Hi all,

Last year I made the boll aero engine but never got around to running it.

Now is the time but need some advice on suitable fuel.

The second photo shows some I found on ebay. Would this be OK?

[BazParticipant @baz89810]

Says Diesel fuel on the label so I imagine it will do the job.

[duncan webster 1Participant @duncanwebster1]

When I was a teenager (long time ago) I had an EDB 1cc compression ignition engine. The local aeromodellers gave me a recipe of 1/3 each of pump diesel, ether and redex. Boots the chemist happily sold me a bottle of ether. The experts could start the engine almost first try, I struggled, never got the knack.

[bernard towersParticipant @bernardtowers37738]

If you can find D1000 you will find it easier for starting. Engine looks very nice.

[half whitParticipant @half-whit]

Hi guys

Thanks for the replies.

Been setting it on a stand which I can clamp to the bench.

Seen the use of a syringe on the internet as fuel reservoir.

I notice Steve Webb models in Frodsham have D1000. Going that way Monday so I’ll call in

[JasonBModerator @jasonb]

Just remember to take the plunger out so it is not sucking against a vacuum.

Engine looks good

[KEITH BEAUMONTParticipant @keithbeaumont45476]

That is a nice looking engine. Cannot understand how you have managed to leave it all this time and not start it up and hear the super noise!

That fuel will be OK. I have used many liters of both 1000 mix and 2000 on various engines and can honestly say I have not noticed either being better at starting an engine. Good starting requires good compression. If you have that and follow a sensible method of finding the point you first get a bang, you will enjoy the experience. If you need any advice just say the word.

Keith.

[half whitParticipant @half-whit]

Hi All,

It’s been a long time and for numerous reasons I’ve not got round to starting this engine.

Well I now have the fuel D1000, so no excuses.

I attempted to start it yesterday with absolutely no indication that it would start, dead as a dodo!!!!

I backed of the contra piston and tried a port prime (with the fuel tank empty). The piston was lowered gradually 1/8 of a turn at a time for further port primes giving each setting 6 aggressive counter clockwise flicks from the front of the engine. Nothing, not a sign of it starting. I can feel the compression but no bangs or any indication the fuel is being ignited?

Could I ask what is a port prime. I realise it is done via the exhaust port, but how much fuel and how is applied through the port? I suspect I may have used to much fuel?

How about the prop, any thoughts?

Geoff

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Hi Geoff,

A port prime is in the exhaust. I squrt it in the exhaust ,about a couple of drops is about right .You soon know if you have overdone it as it will be difficult to  turn over. The six flicks give the fuel a chance to distribute to the correct vapour.  How far down did you wind the contra?  Do you have compression pressure that feels bouncy?  If you think you have put in too much fuel, flick 12 times before any further prime.  The prop in your photo looks about right. what is its diameter and pitch?

Dont give up!

Keith

[Kiwi BlokeParticipant @kiwibloke62605]

Geoff. Very pretty! You can be proud of that!

It’s not clear whether you’re new to compression-ignition engines or not. Assuming novice (apologies if wrong..), little engines can be awkward little buzzers because you have to juggle compression and mixture adjustment. Usually, you can get at least a pop if the cylinder is ‘wet’ with fuel, squirted into the exhaust port (‘port-primed’), and the compression is high enough. A squirt directly into the air intake is also a good idea – see later. The engine may run for a few seconds on the ‘prime’, if the compression is OK. However, remember that the engine relies on fuel getting into the crankcase for lubrication, so I’d suggest having a bit of fuel in the tank, and that’s why an air intake prime is a good idea. Don’t let the fuel feed by gravity, or the crankcase may get too much liquid fuel. Keep the fuel level at, or just below the level of the spray bar. The amount of compression required may surprise you, if you’re used to lawnmowers, chainsaws, etc., so don’t be shy of winding the contra-piston down – just avoid a mechanical crash or an hydraulic lock. Plenty of info on adjustment can be found in the usual places. A large-diameter prop is a good idea, for flywheel effect and easier starting, and to keep the revs of a new engine low, for running-in. Good luck!

Keith beat me – I’m a slow, two-fist typist… Clearly, a lot of advice available here…

 

[half whitParticipant @half-whit]

Hi Keith/Kiwi,

Thanks for the replies.

Still no good. I’ve had another long session today with no improved results.

I’m starting to question the build quality/accuracy of this engine. Have I got something in the build fundamentally wrong. I would be surprised if that’s the case, but maybe I have?

Have another go soon. The prop is 8 x 4. It feels a bit light, I can’t seem to whip up any speed with it?

Thanks again Geoff

I won’t give up!!!!

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Geoff,

With the port prime method, the only part of the engine quality that is coming into play is the  compression pressure. It is in the name, Compression Ignition. If the compression pressure is not good enough you will never get a bang. When you turn it over by hand,using the prop,can you feel real resistance at  TDC? How tight is the Contra Piston? That should not leak and you should have a comfy resistance when you wind it down. Are you putting the prop at 2 o’clock coming up to compression? This gives max pressure at TDC as you flick it. Also, use a stick to flick it. You get much more action than using a finger, even if it has protection.

Good luck.

Keith.

[half whitParticipant @half-whit]

Hi Keith,

I believe now that this is now a compression problem as indicated in your latest post.

I dismantled the engine just to check things out sizes, fits etc and discovered that contra piston is weeping fuel when under pressure. The piston is fine, I lapped it up tdc and there is sign of any leakage or lack of compression.

The attached photo shows the cylinder with the piston supported at tdc. With some fuel on the top of the piston I then inserted the contra piston and forced it down with plastic pen. Note the bubbles around the outside.

The contra piston felt good when I first assembled the engine but clearly not!!!

New contra piston to be made, which in itself will quite a challenge for me.

Report back in due course

Geoff

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Hi Geoff,   It looks like you have found the problem!

The best way of making a contra piston that does not leak is the tapered method. Bring you blank down to size plus .040″ or 1 mm. Bore the blank to a size that should leave the  final wall thickness at .020″ or .5mm and part off. Make a stub mandrel to fit this diameter, with a threaded hole through centre. Super glue blank to this stub mandrel. The theaded hole is so you can put a screw in to push the finished contra off the mandrel with heat applied.

Set your top slide over to .5 of a degree and turn the outside to a good finish, checking the fit into the cylinder often. When it starts to enter change over to using a flat surface with some wet and dry on and reduce fit until it is about 3 parts in. At this point remove from chuck and apply heat to soften glue, using the screw to push it off the mandrel. The taper will ensure you have a gas tight fit. I apply some copper grease  to it when  I finally fit it. For the past 4 engines I have made , I have used mild steel for this item rather than CI. Other will frown on this, but I find it works.

Hope this helps.

Keith

[Author]

Posts