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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: BMFA kick backs/discounts for clubs
29/09/2020 21:25:20

Well said John.

I was lucky enough to join a club which bought its own field back in 1982 - members lent money, raised money, took out a mortgage and worked extremely hard to turn rough scrubland into the great field that we can enjoy today. I hope my own small contributions to maintaining and improving the facilities reflect what we owe to those members' efforts to some extent.

Nobody gave us any grants - although I understand that the local council offered us the use of the town centre shopping arcade's top storey car park on Sundays (this was before Sunday trading of course) while the club was "between" rented sites...surprise

The club has benefitted immensely from the far sightedness of those members who persuaded the doubters within the club to make the investment and if there's a club out there that gets the opportunity to buy their own site, I would say give it very serious thought - when I hear tales of clubs paying several thousand pounds a year on rent it makes me feel we're very lucky indeed.

Edited By Martin Harris on 29/09/2020 21:32:14

Thread: Jet Pack Paramedic - Coming to a Hillside Near You!
29/09/2020 13:19:07
Posted by Robin Colbourne on 29/09/2020 10:34:53:

How does the thrust from the engines support the pilot? Surely he's not taking all the load through his arms for the whole flight?

I have to say this was my first thought and makes me suspect this to be some sort of elaborate hoax - maybe someone can confirm that they've seen one of these set-ups working, first hand?

Thread: BMFA kick backs/discounts for clubs
29/09/2020 12:55:40

The 400' exemption seems to me to be the visible tip of the iceberg of credibility that the BMFA has built up. It, along with the LMA, SAA and FPVUK seem to have become organisations respected by the CAA which is happy to devolve certain aspects of control and administration to them.

Of course, various individuals will always claim that better ways of doing things could have been adopted - especially when they have the benefit of hindsight - but generally the BMFA have a pretty good record of assisting clubs and individual members and I'm happy that the organisation is looking after my interests far better than I or my club could ever do alone.

It's an old chestnut but if some people have better ideas, why not get involved where they can contribute far more than sniping from the outside?

28/09/2020 11:31:41

If your club's bank won't allow transfers then it's probably time they changed banks! We actively encourage our members to pay subscriptions by bank transfer - and any money I spend out on the club's behalf as a committee member is credited the same way.

Thread: Best interference free 2.4 tx under ?350?
25/09/2020 11:32:23
Posted by Brian Cooper on 25/09/2020 01:57:54:

I was asked to test-fly a new Wot 4 XL for a club buddy recently. It was (is) equipped with Multiplex equipment. . A couple of minutes into the flight, the ailerons reversed themselves. crook . . It was certainly a challenge to get it down, but the main thought going through my mind was, "what else will reverse before it lands?"

It was landed with no damage, and we reversed the ailerons back. The only thing we could attribute the problem to was my buddy having a mobile phone in his pocket. . Much head scratching. .....!!

. . . .

Spektrum DSMX has proved to be bomb proof for me for several years.


Wasn’t it a Multiplex transmitter which was proved to be prone to programming corruption back in the early days of debate over whether mobile phones were a hazard near the flight line? As far as I know, it was the only repeatably demonstrated example of a problem.

Thread: Ofcom trace interference to a lightbulb
24/09/2020 17:40:00

We told apprentices to pop into the stores and ask for a long weight (after explaining how the return weights for switchboard cords came in different sizes of course).

The word bulb probably only appeared in the stores rate book (roots deep in GPO/Civil Service origins) in connection with wet and dry bulb hygrometers.

24/09/2020 16:12:18

The link hidden at the bottom of Martin_K's post gives a very plausible explanation...essentially, yes - the filament length is at the root of the phenomenon.

24/09/2020 15:41:28

Far from being a rarity, I think the lamps* ("Bulbs? Bulbs is wot you plant in your garden" was indelibly knocked into me by our storemen at work) used in my house have at least reached parity between ES and bayonet and I suspect ES are well in the majority.

*Full title: Lamps, incandescent.

Edited By Martin Harris on 24/09/2020 16:02:01

Thread: The Gov't, CAA, BMFA & UAV legislation thread
23/09/2020 15:30:49

I read it as the autonomous drones will (hopefully) sense and avoid other airborne objects - the zone being a defined area where the autonomous drones will be operating.

Edited By Martin Harris on 23/09/2020 15:31:30

Thread: Premier 1/4-scale piper cub J3 cockpit
22/09/2020 00:44:29

Photos of the plans sent - let me know if they don't arrive...

21/09/2020 13:20:23

There definiely was a manufacturer called Premier - and at some time this design was also sold as Aerotech.

I don't want to let go of my plans Paul - and having witnessed the copying process at my local branch of Staples I don't think the rather aged paper would survive the copying machine - but I'm more than happy to photograph them for you to add detail to your overlay idea.

Edited By Martin Harris on 21/09/2020 13:20:54

21/09/2020 10:06:25

I don't think Paul is quite ready for this - the panel request is nearly a decade old!

I do have a copy of the Aerotech build notes I could send - identical to the Premier kit.

PM me your email address...

Thread: larger models
20/09/2020 19:26:14

I'd agree with that. As a rule of thumb, I'd say that a 2 stroke petrol is roughly the equivalent of a 4 stroke glow.

Thread: Pre-ignition ?
20/09/2020 16:08:44

Cold air is more dense than warm which might have tipped the balance towards knocking. I've found that a lightweight propeller can also contribute due to reduced flywheel effect but you seem to be using the same one on your other engine.

Could the one that knocks be a little carboned up? It wouldn't take much build up to cause hot spots and increase the compression ratio a little.

Thread: Import and VAT
17/09/2020 00:13:03

I was just quoting Irvines - perhaps an oversized bore 1 1/8" OD bearing with a suitable width would make more sense?

Thread: 4 motor watts
15/09/2020 18:36:28
Posted by Ronos on 15/09/2020 16:59:51:
Posted by Martin Harris on 15/09/2020 15:34:05:

I think the only time you put a prop on backwards is for a pusher motor/engine i.e. the motor/engine is pointing backwards. Reversing a propeller simply makes it produce thrust in the same direction - but horribly inefficiently.

It might be worth training the ESCs on the AUX channel separately.

Edited By Martin Harris on 15/09/2020 15:36:25

Hello, I am not putting a prop on backwards , the set requires 2x standard props and 2x pusher props

I didn't think you were - it was Ben's confusion that I was addressing...

15/09/2020 15:34:05

I think the only time you put a prop on backwards is for a pusher motor/engine i.e. the motor/engine is pointing backwards. Reversing a propeller simply makes it produce thrust in the same direction - but horribly inefficiently.

It might be worth training the ESCs on the AUX channel separately.

Edited By Martin Harris on 15/09/2020 15:36:25

15/09/2020 01:36:56

Do you really mean that all 4 props are identical or are two of them pushers? If the latter, it might be that despite the sizes being identical, the pitches are a little different. Swapping them with the other pair and reversing rotation of the motors before measuring again would prove this.

14/09/2020 23:28:14

It looks as though the additional load of running all the motors from the one battery has dropped the voltage significantly. As power (W) is derived from voltage (V) x current (I) the result will be to reduce the total power.

If you connect the second battery in parallel with the first, the voltage drop will be much less and the result should equal or be very close to the sum of the two readings.

Were the readings all taken from the same battery or was one pair connected to each battery?  If so, swap the batteries and see if the difference moves with the battery.  If so, one battery was either undercharged or is not as good as the other.  Otherwise, are the motors/props identical?  Have the ESCs both been trained to your transmitter? Have you removed the red wire from one of the ESCs?

Edited By Martin Harris on 14/09/2020 23:33:16

Thread: New limit on groups in England from Monday?
14/09/2020 11:19:23
Posted by Keith Miles 2 on 14/09/2020 08:57:20:

Why some people seem to feel that a simple signing in procedure, especially in the current circumstances, is a big deal, baffles me and “scapegoating” gets us nowhere.

I assume this is aimed, if not exclusively, at me and I'm not sure who is being scapegoated but it's simply from experience with getting our members to adopt any new process. Your established procedures may help greatly in this situation but we need something which is not only simple but will be viewed as such. I feel that we'll have more success with using the official NHS app (assuming it is released soon) than trying to convince elderly members to go on line and use a "shock! horror!" spreadsheet - although we might be able to avoid using the term. As an example, we went to great lengths to produce and publicise a website to allow members to keep up with events and contact each other - less than 20% of the membership had ever logged in to it when I had access to the stats.

Do you have a suggested simple to access on-line spreadsheet that I can take a look at?

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