Could I ask you a couple of questions
1). A few weeks ago you were discussing the fact that the front cylinders of
your engine were getting hotter than the back 2... Using your u beaut MGL CHT
sensing system. When I put our Dimona's engine together. (And a Grob 109 with
an L2000 engine) used the standard Limbach shells but redesigned everything
else. All good I thought.
I installed a Westach dual CHT on the rear 2 cylinders of the Dimona and just
recently the same on the Grob 109. However as the rear plug is a bitch to
remove, I installed one of the sensors on a front cylinder. .. Flew it for
the first time on Sunday and clearly about 30 plus degrees hotter than the
rear. 200 plus which is just too hot.
My question relates to the Limbach shells. Looking at them it would seem that
there is too much of the head blocked off at the front restricting the flow
around the head at the front. So I am planning to remove material from the
front shells in line with the top exhaust bolt on each side... What do you
reckon about that ?.
2). I have a Great Plains secondary ignition system in stock and am seriously
considering installing it on the Dimona ( after the recent mag failure). What
do you know about the drilling methods of installing the second plug. Is there
any published data about doing that anywhere that you know of.
Sent from my iPad
> On 21/09/2016, at 7:26 PM, Ian Mc Phee <mrsoar...@gmail.com> wrote:
> Interesting both spacer of Rob and Ian's issues.
> My bloke always fits new condenser & points (in glider lives these spares
> plus the cog wheel following Rob Handbury failure at Burketown last year) In
> older electronics capacitors do dry out and fail. 10+ yrs ago we had think
> 4430 fail in coil and LAME said it was overheating so since then always add
> a jet of cooling air to magneto.
> I use the fancy Limbach plugs all pre set but usually carry a spare car plug
> but what is the suggested gap? . Think I remember 0.6mm or was it 0.55 mm on
> magneto and 0.7mm on back up electronic ignition. Anybody remember? I seem
> to remember reading car plugs life is 150hrs but fancy plugs is 500hrs but
> can't find it.
> Ian McPhee
> Box 657 Byron Bay NSW 2481
>> On 21 Sep 2016 8:22 am, "Rob Thompson" <post...@hotmail.com> wrote:
>> G'day all,
>> Just a reminder that there needs to be an appropriate gap between the
>> flywheel and the metal coupling on the magneto.
>> That is, the rubber spider must be the only contact between the engine and
>> magneto. Metal to metal will stuff your magneto bearings, effect the engine
>> balance and transmit crankshaft harmonics straight into the magneto.
>> The measurement process is detailed in the manual and appropriate gaskets
>> can be installed. This technique only works with the engine out.
>> If you are installing the mag in situ, I have only found one way to check
>> the gap. Put blobs of blu-tac or plasticine on each outer point of the
>> coupling and slide the magneto into place. The blu-tac will squash down and
>> you can pull it out and measure the gap. Don't just install the magneto with
>> the same spacer gaskets and hope for the best.
>> You can hold the magneto at the timing point with a bit of appropriately
>> placed masking tape which will disintegrate as soon as you start the motor.
>> Rob Thompson
>> 0429 493 828
>> From: email@example.com <firstname.lastname@example.org> on behalf of
>> Ian Williams <ag...@xtra.co.nz>
>> Sent: Monday, 19 September 2016 7:43 PM
>> To: email@example.com
>> Subject: [DOG mailing list] Dimona ZK-GCB
>> Of interest, we have had some Mag problems with our Dimona. (Slick)
>> I had just completed its annual inspection which included the 2 yearly Mag
>> bench check where both main bearings were noisy so were replaced. The bench
>> test was quite normal. Then reinstalled in the aircraft (not the easiest
>> with a Dimona as you would know).
>> A ground run was done … all normal, then a test flight … again all OK.
>> However during a second test flight, at around 800 feet, the engine suddenly
>> lost power. It would still run … (well sort of) but could not maintain
>> height, so a precautionary landing was made back on the airfield.
>> I took the mag off and back to the engine shop. .. on the test rig, no spark
>> at all. It was pulled apart and the condenser was stuffed. A replacement
>> installed and all good again.
>> Still need to reinstall on the aircraft.
>> This mag / engine had a forced landing in Thailand about 12 mths prior to
>> their decommissioning. The engine was sent back to Limbach and was
>> re-lifed, so we were real fortunate that it was zero timed. But not sure
>> about the Mag. The engine has now about 160 hrs TT (also SMOH) in New
>> I assume the mag was also the original. We had it bench tested 2 years ago
>> prior to the first flight in New Zealand. All OK.
>> When the mag was pulled apart, the condenser had what looked like somebody
>> had put some araldite around where the wire comes out of it. Presumably to
>> avoid any strain on the connecting wire. However it also just may have been
>> leakage from the condenser.
>> So it may be something to consider with the ex Thai Dimona’s that the
>> condensers in the Slick Mags really need to be replaced if there is any
>> doubt that they are still the original.
>> I think there is actually a date stamp on the condenser which could prove
>> Ian Williams
>> New Zealand