Starting a motor for the first time

[Peter Christy]

Manny: Glad you got it sorted!

--

Pete

[Mannyroad]

Thanks.

I've put two tanks (8oz) through my new SC25, during initial run-in, and its loosened up great and the transition between a fairly low tickover and full throttle is pretty good. Surprisingly I found I had to slightly richen the low end mix to get this because when I did a pinch test on idle it just ran on and on. However what I'm finding is that, if held on normal idle for 15 secs it starts to die, and cuts by 20 secs. regular as clockwork.  I also find that if I try to transition quickly from a fairly fast idle it bogs and struggles to pick up, but surprisingly I'm not finding much evidence of bogging from normal idle speed.

Any thoughts on this would be appreciated. If a vid would help I'll do one, it just take 30 mins to upload any vid I do onto Youtube (not sure if there's a quicker way to upload or not).

Edited By Mannyroad on 26/02/2017 13:25:59

[Denis Watkins]

Manny, you suggest "new" and running in

So don't be disappointed with the tune just yet

Run it in some more, it will still be tight

And don't overheat it

Maybe 5 minutes at a time, until a few more tanks full

Then we fine tune again, but I would put the low end back where it was for now

2 or 3 more tanks, then come back

Edited By Denis Watkins on 26/02/2017 14:39:11

[Mannyroad]

👍

[Mannyroad]

Fair point Denis, I will put low end setting back and give it a bit longer as you suggest. I don't run longer than about 3-4 mins before allowing to fully cool in this period.

Generally I run a half tank through (4oz - my test stand has an 8oz tank) doing 2mins at full throttle - 2 stroking, then around 30 secs of 4 stroking, alternating this way till half tank is used. Then I allow to fully cool down before repeating all over again. I normally do this for about 3 full tanks, i.e. 24oz of fuel, tweeking the needles as things change. After this I put it in the model.

I'm perhaps like others, never really ask how anyone else does their run-in procedure. I've always done it this way, give and take. What's your procedure?

[Denis Watkins]

You won't thank me for this Manny, but the bulk of the running in is completed in a model, with absolute certainty of acceptable tickover and throttling, I run them airborne on the Boomerang. This model is my "running in " platform, nice and cool in the air, no aerobatics, just smooth circuit flying.

Prior to that is much as you have done, a couple of tanks securing a good idle and ensuring no unplanned cutting out.

The motor then goes airborne on the hack for about one week of good flying weather, which usually amounts to about a gallon of fuel, while I get it set up, then it goes on the final model.

This amounts to approximately 1 motor per season on a new model, as I am more a prolific flyer, than a prolific modeller

[Peter Christy]

Depends on the engine! In days of yore (ringed, cross-flow engines), a couple of tankfulls quite rich, followed by leaving it on the rich side for the first few flights was considered the norm. The main thing is not to let the engine labour or overheat.

Modern engines usually require far less running in. In particular, ABC engines are probably best run-in in the air (better cooling than on a stand), slightly under-propped (prevents over-loading) and just a tad rich - definitely not slobbering! Keep the flights short at first.

Those of us who fly helicopters don't have the luxury of being able to run them in in the recommended way. We usually just bolt them in the airframe, leave them a tad rich for the first few flights, and keep initial flights short. Never seems to do any harm!

Just as vastly improved manufacturing processes means that modern cars need little if any running in ("Don't tow a caravan for the first 500 miles, sir!", so most model engines require little running in compared to the motors of yesteryear.

As I say, a tad rich, keep flights short, and don't over-load it, and it will bed in in no time!

--

Pete

[TIM Shaw]

That depends on whether the engine is a ringed type - in which case I would do something similar, but in a model rather than a test stand, and I'd fly it, albeit slightly rich for the first half dozen flights or so.

For an ABC type motor though, I'd absolutely NOT go through this type of procedure, mount it in a plane and go fly it, tweaking the bottom end after each flight if necessary, and while taking care not to get it at all lean, I'd not run it deliberately rich either.

Why? because I believe it is important it wears in under the conditions you are going to use it, in particular the cooling characterisitics of an engine in flight are very different from those on the ground. I would probaby leave a full cowl off though - you really don't want any cooling problems either.

But thats just me.......

[Mannyroad]

OK guys, cheers for your views on this.

Seems the general consensus is to bolt a brand new engine straight into a plane and fly it, slightly rich, short durations. It's funny though, how over the years we get varying views. There was indeed a time I recall fellow modellers advising me to always bench run it first to loosen it off before putting it in a plane to avoid the risk of deadstick landings on first flights. I kind of took this on board and have always done this. maybe for engines of yesteryear this was what we all did, I can't say, I just know I took the advice on board and did it this way. maybe I now need to review this in the light of improved machining of engines. Cheers for your comments, the 25 will go airborne now.

[Jon H]

running in is an interesting issue and causes us some issues as many customers are still doing it the now out of date way (slow rich runs) and running into issues because of it.

Our engines are ringed 4 strokes and yet we recommend running them fully lean, ie no rich running at all, from day one. This is extremely important as it gets the engine up to operating temperature quickly and it allows the engine to run in like this with all the parts properly expanded. The oil also works better when its hot and the high piston velocity is good for the iron rings. All we ask is that the engine is not loaded with a big prop and is not run at full power for long periods.

In truth however you could more or less do what you like with it and the other day when testing a batch of 70's each was wound up to 11000rpm and left there for a solid minute before slowing down.

In all honesty, running in is not a big issue any more and should be done in the air. No more than a 5 minute run on any engine on the ground before getting it up there and all this nonsense about running rich for 5 years before leaning it off a click at a time is simply out of date.

[Andrew Davies 3]

how "oily" should a motor run when new? I stood behind mine earlier to give it a run, with my legs (in wellies) in front of the tail to hold it steady, and noticed that the wellies were quite wet after 5 or 10 minutes running. The side of the plane is quite oily too?

is this right?

[Don Fry]

Jon, and I believe he may have some knowledge of engines says, lean it off till it peaks, but no more. When you go to the moving the needle bit, but the moter does not alter, you are in the danger area of a lean run. Peak power, but not lean.

In the plane, plan to push air through the cooling fins. Air will try to do a lazy route, not through the fins. Plan to push it where you want it, to take heat away. It is an active process, not a hope process.

When it runs hot, they stop after a bit. And then we complain it is unreliable.

[Denis Watkins]

Hi Andrew, there is some oil from the silencer, and if the model is static, with the outlet pointed at the model, then some oil will collect over that time.

The silencer is marginally adjustable, and the outlet can be directed away from the model, and in the air, the oil will not collect as much

If the engine throttles and idles properly and fly's well then accept some lubricant

If the needle is set very rich then this would account for some oil

But there will never be no oil ejected

[Jon H]

two strokes tend to be quite messy, but if you are running rich it will be even worse.

Donald's comments are fair but to elaborate further and get our terminology straight there are 3 conditions the engine can run in:

Rich - too much fuel
Optimum - pretty self explanatory
Lean - insufficient fuel

In a rich state the engine runs at reduced power and is not very smooth. It will also run cool.

In a lean state the engine again will run at much reduced power and will likely overheat and stop in fairly short order.

The optimum state is the range of the needle where adjusting it makes no difference to the rpm or performance of the engine. go outside of this range one way or the other and you are either rich or lean. Some will call this peak performance 'lean' and they are incorrect to do so as the engine is not lean until there is insufficient fuel to maintain combustion. Anyone who has used oxy acetylene welding torches should know what I am on about.

when tuning your engine, wind it up to full chat and slowly close the needle until the engine is near what you think is peak rpm. Then slow right down. Lean it off in small steps with a gap in between. I would go 2 clicks and wait, 2 clicks and wait and keep doing this until you hear an rpm drop which is where you have gone lean. Then go back 2-3 clicks and you are all set.

If the engine overheats and stops in flight you have two possibilities. One, it overheated and needs better cooling as Donald suggests, or two it went lean as the tank was too high to begin with and the drop in fuel level caused a lean cut. In neither case will richening the needle be the correct solution!

The above is not 100% of the story and some engines, usually 4 stroke will need perhaps a click or two richer under certain circumstances. A friend SC70 for example wanted about 4 clicks back after hitting the lean point as it had a little knock when only 2 clicks back. Its not the sort of thing most would notice, and at that point we really are getting into the finer points which is beyond the realms of what model modellers will care about, and as it was not enough to damage the engine it was hardly worth worrying about anyway. I just like perfection in my engines and the ones around me

Edited By Jon Harper - Laser Engines on 26/02/2017 22:34:46