Crash investigation - taken ages to find the cause

[PETER BRUCE - Eastchurch Gap]

Yet again I have a brand new AcrowotXL (no 3) and this time I will fit the usual upgraded parts (control horns & clevices) and now a dual battery bus bar system with an electronic switch - the latter is in place of the slider switch that failed on AcrowotXL number two... I really like this plane and a 35cc petrol aerobatic was a new venture for me a few years back from the usual scale biplanes which I normally fly. The extra strains on a more powerful larger aerobatic plane puts on the components has been some tough lessons to learn as what is satisfactory on smaller models just won’t cut it on a large aerobatic plane. Another factor regarding slide switches which I found on stripping down some old ones I had in the spares box from long deceased planes was interesting because I also found oil coating the internal slider contacts - not much, but how much does it take to affect the contact ability? The glo fuel oil gets everywhere and if there is any castor content in the fuel - I am sure that clammy jelly glaze that you find in your old engines must affect the slide switch contact ability so I wonder if the slide switch issue is even more prevalent than I suspected.

If you have any old slider switches in your box of spares - never use them - but strip one down and have a look for the oil ingress as glo fuel gets anywhere and if you have ever used any fuel with any castor oil content it would be interesting to know what you find. Regards Peter

[Peter Robinson 9]

Hi Pete

Any info/pictures of the unit you are going to use.

Peter

[Tim Flyer]

One idea I use with slider switches ( I often use Futaba Heavy Duty) is to put them inside the model where possible. Then they don’t get the oil coating.

[Ron Gray]

OK, so this is slightly off topic but in some ways it isn't! If slide switches are potentially such a risk, what is the best alternative, magnetic switches, pin switches? Or maybe this should be a topic in its own right on the forum?

Edited By Ron Gray on 24/10/2018 11:58:00

[Paul Marsh]

The best were these, sold by SM Services, but they are now gone.

However, think RS sell them.

[PETER BRUCE - Eastchurch Gap]

Just got back from work and got a few goodies to look at. Pin switch, dual battery system... lot to learn. Thanks Peter for the items to look at you kindly brought to the flying site Saturday for me to look at. I am intending to upgrade both my Albatros and Sopwith Pup to remove the slider switches from the equation as to lose my converted Albatros IC model would break my heart after all the time spent on it - as far as I am aware it’s the only Maxford USA Albatros out there running with a 120 four stroke engine in... My Sopwith with its twin four stroke is also one I don’t want to lose so the slide switch in that is going... will keep you posted but at the moment things are a bit hectic so not much time to play to find our where I’m going but be assured I will be monitoring. Regards Peter

[PETER BRUCE - Eastchurch Gap]

Made a start on the new AcrowotXL - we’ll the DLE35 engine actually as the cooling fins on the engine head were all broken on one side so the whole head had to be changed. Washed out the crankcase and no bits inside so that’s a bit of luck. On the switch front I was lucky to have a club member (Peter) loan me a few to look at which are the magnetic type and that’s the way I’m going to go. To alleviate any possible problems I’m going to use a power panel as well as the bus bar system inside them has got to be better than the bus bar in the Rx. Not in a mad rush to get this model done and I’ve ordered a 12v 5kW diesel air heater - the self contained unit all in one they fit into trucks and motor homes but I’m going to put it in my shed so I can work up there during the cold weather. Yesterday I tackled the lighting problem I had and I’ve installed a 5 foot batten LED fitting which gives an instant good light level and is better than the old flo fitting I had in there. The heater is due in the first week in December so once fitted I should be all set to work outside and the 5kW heat output should keep me toasty. I will show the progress of the switch situation. Regards Peter.

[Keith Sharples]

Hi Peter. With the diesel heater I would suggest that you put it inside a muffler box, make some form of box which will deaden the sound of the heater running as they can be quite noisey but please make sure there is a large air gap all around the heater as well as ventilation to allow any build up of heat from the heater casing to vent out of the box. With the heater inside the box, then use foil lined ducting on the air input and heated air output directing the output duct to where you want it. Also make sure the heaters exhaust pipe is vented and sealed to run outside your shed, you don't want the shed to fill with fumes!!. Really follow the heater fitting instructions and use common sense and you shoudn't go wrong. I used to fit loads of these when I was in the caravan and motorhome industry.

K

[PETER BRUCE - Eastchurch Gap]

Hi Keith. Thanks for the warning. I am aware of the problems and it’s one of the reasons I went for the all in one unit in the metal case as opposed to the usual loads of bits in a box package most use for cars vans and trucks. I’m going out the side of the shed with the 25mm one piece stainless steel exhaust and will sleeve the hot exhaust with proprietary exhaust tape so no heat can transfer to the wood shed construction. The combustion air inlet will also be taken from outside. I will be fitting a Carbon monoxide alarm - just in case. Regards and thanks for your concern. Peter