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Member postings for Martin Harris

Here is a list of all the postings Martin Harris has made in our forums. Click on a thread name to jump to the thread.

Thread: Not a fluorescent jacket in sight!
26/05/2017 18:11:23

Crowds were made of sterner stuff in those days...none of that 30m separation - just point your freeflight model at the crowd line and watch them duck!

Thread: Range check and signal loss
26/05/2017 18:07:09
Posted by gangster on 26/05/2017 15:51:25:

do not however overlook the transmitter switch and corrosion. Check it carefully. They are a poor quality component on ALL makes of radio


Thread: Landing a Dynam Spitfire
26/05/2017 13:04:56

Too windy to fly? Cut the grass!

Thread: Anet A8
26/05/2017 12:56:21

Posted by Robin Etherton on 24/05/2017 15:08:00:

Incredible at the differences in belt alignment between various builds! Even with the h piece facing down I still needed the additional spacer to get it in line.

Just a thought Robin - could your X and Y steppers have been incorrectly marked? They come pre-assembled with the belt pulleys and the only obvious difference between them is that the pulleys are reversed.

Edited By Martin Harris on 26/05/2017 13:02:31

Thread: stuck to one Manufactures 2.4Ghz protocol no more
25/05/2017 10:27:29

A good point. It was interesting to see a long time exponent of the capable, but budget Taranis transmitters say that he wouldn't trust these modules because they were cheap! I believe that the more expensive equipment's advantages lie mainly in the mechanical and build quality side - I was fairly horrified to see the internal details of the Horus, for example, with wires running higgledy piggeldly and splodges of hot melt glue everywhere. Corners cut on switches and pots can easily bite you a year or two down the line.

Having said this, price is no guarantee of quality though - witness the recent debacle of a well known and very popular manufacturer's newly released top of the range transmitter which was recalled after finding that the sticks were fouling internal wiring!

Thread: Anet A8
24/05/2017 19:49:56

Fingers crossed - sounds like you're doing a thorough job...

I've no experience of CAD but I've messed around with a free program called Tinkercad which seems quite intuitive - as an exercise (and in preparation for a useful and more accurate part for my current build) I've knocked out a Tempest(ish) exhaust stub quite easily. I used Cura for the slicing...

Still very much at the learning stage - there seems to be a minimum size that is practical - my first (very small scale) six stub manifold was a disaster but a single stub at slightly larger than model scale seems quite acceptable...


24/05/2017 12:48:24

I see what you mean now - looking down on my belt shows a slight misalignment (maybe 1/16" at the middle?) but I haven't noticed any binding at the extremities or effect on operation. It might be worth correcting though - good spot!

My Y axis H crosspiece is uppermost and the belt seems to be properly aligned.

23/05/2017 21:41:40

I'm not sure which longer screws you are referring to on the Z belt, Robin? As I understand it, the Z axis is the one operated by the twin leadscrews...but I didn't find any problems with any of the screw lengths. There again, I didn't realise that there was a manual on the SD card and worked from a manual on the net and the videos I linked to earlier...blush

Thread: Stuka Siren
21/05/2017 22:13:55

But doesn't the siren increase in pitch as the airspeed increases - or did they have a speed regulating mechanism?

devil's advocate...

Thread: How do they do it for the money?
20/05/2017 21:24:10

I built the Black Watch as well - the electronics were fine but the mechanical side was rubbish . After a few months I ended up with one of the first digital car clocks - built the internals into the centre boss of my steering wheel...and replaced the dodgy flexible pcb touch contacts with some of my Mum's pins pushed through the boss and wired to the board.

Happily, I was never tempted by the C5 - although I did have a go with one round a car park...a bit of fun but a joke as a road vehicle!

20/05/2017 14:24:14
Posted by John Privett on 20/05/2017 09:48:54:
Posted by Peter Miller on 20/05/2017 08:13:48:

"Reverse Polish logic"

A school-friend brought his Christmas present in to our Additional Maths A-level class in Jan. '76. (It was a small class - 3 of us I think, we'd done the 'regular' Maths A-level a year early) That was a Sinclair Scientific calculator and used Reverse Polish Notation. I think we (3 of us + maths teacher) spent most of the lesson playing with it...

That takes me back. I built a Sinclair Scientific programmable calculator from a kit, which cost an extortionate amount of money at the time (£20 odd in the early 70s?). If memory serves me right, there was a simpler version (the Cambridge?) which used a smaller battery - the Scientific had a lump at the back to accomodate a PP3. The calculator disappeared decades ago but I still have the books of programs somewhere in the loft.

Thread: Anet A8
19/05/2017 19:53:47

Thanks - lots to learn!

19/05/2017 16:09:59

I'm a happy bunny - test print worked fine although I think I selected the wrong filament type as the nozzle temperature went up to 220 from 190 which I'd originally selected after nothing happened when I followed some video instructions - found a menu which seemed to be for various filament types and selected one - whereupon it burst into life...

Now all I've got to do is work out how to use it in anger...and remove the print from the bed tape. Is there any reason why people don't simply remove/replace the masking tape between each print?

19/05/2017 12:22:10

I'd be interested to know if anyone else has had Z motor alignment problems - is this something to do with the later modified X axis motor and idler parts - especially from Robin with his contemporary machine?

Once assembled, the leadscrews didn't align properly and loaded up the mechanism, meaning that manual lifting of the print head by winding the motors was difficult and I'm sure such loads wouldn't do the motors and machanism any good. I have treble checked that there was no "wrong" way to assemble the motor cradles but I couldn't see another way.

To solve it, I machined slots in the acrylic cradles and it now aligns and moves much better. Drilling and filing should do it but as I have a small milling machine I used that. The acrylic is a pig to machine - the cutter has to move soooo slowly or it simply overheats the plastic and melts it onto the cutter! I might have got away without recessing the underside of the coupling hole slightly to give clearance for the flange round the motor shaft but it was easy to do while I was milling the slots.

I suspect that the mosfet mod isn't quite as important as my version has screw connectors to the PCB rather than a plug and socket arrangement which seemed to be the source of overheating from a little research - but I'm fitting it anyway!

Edited By Martin Harris on 19/05/2017 12:25:12

Thread: What Engine for a yt Dragon Lady?
19/05/2017 00:06:28

Identity theft? Call in the mods!

Thread: Pilot Bails Out At Low Level
18/05/2017 23:09:30

I fly my >7kg models with an altimeter - we have a 400' height limit for them and it's just enough to do a decent loop...

18/05/2017 21:50:30

I could be wrong - it was a very long time ago! Where's a bomb aimer when you need one?

18/05/2017 21:26:16

Acceleration due to gravity isn't linear though - until an object reaches terminal velocity (drag equal to force exerted by gravity) it continues to accelerate with the square of time (ignoring drag which also increases similarly).

At least, I think that's what my physics teacher told me - and I think he was old enough to have got it from that nice Mr Newton...

Thread: Un-even cylinder temps
18/05/2017 21:14:01

Is one too hot or the other not getting to normal temperature?

Valve clearances, piston ring not sealing, poor cooling airflow?

Edited By Martin Harris on 18/05/2017 21:17:06

Thread: Pilot Bails Out At Low Level
18/05/2017 20:47:24

I'm sure we'd appreciate his input...

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