Here is a list of all the postings MAD Dave has made in our forums. Click on a thread name to jump to the thread.
|Thread: How to reduce voltage?|
I don't believe significantly so. A forward biassed semiconductor (eg, a diode) of the silicon variety will, under normal circumstances, always exhibit a voltage drop between 0.6 and 0.7 volts; in parallel or not!
Place some diodes in parallel to share the load, ie, heat. Recommend the same spec. devices.
|Thread: 1/6 Westland Whirlwind|
Where's the best place to acquire a selection of those plastic topped pins please?
|Thread: How to set flaps on a Futaba 10J Transmitter|
Slightly off piste but still 10J. I am left handed and have always flown Mode 3; ie mirror Mode 2. I recently acquired a 10J, Tx arriving as expected set to Mode 2. Removed the back and (carefully) rearranged the mechanics to Mode3. I now find that ex-throttle/new elevator stick exhibits a servo offset at stick centre position. Have I been unlucky with my specific purchase or am I missing something? Have checked all offsets within the menus I can find and they are all zero. I am able to get things to where they should be with a stick trim offset of 32. Anyone else have experience of Mode 3-ing a 10J Tx?
Re Tx batteries, I have flown many years on a couple of sets of x4 Panasonic 2050mAh AA NiMh cells in my 6J; never had a problem. Intending to employ them with my 10J.
|Thread: Which was the best decade for the hobby?|
fao Piers - Wareham!
|Thread: Latent Servo Response|
Thank you everyone for your thoughts, much for me to think about now.......................
Many thanks for your contributions so far Gents, lots for me to consider. I did wonder about contact resistance, at the plugs/sockets. I had your point in mind Brian and started to wonder about dis and reconnecting everything as an occasional routine maintenance activity on all my airframes. The Pulse has been stored in my (integral to the house) garage over the winter so far. Not perhaps the greatest of storage environments but less damp and cold than some other places. I have not tested anything since returning from our flying field, just parked the remains in the hanger for now. Tx is always kept indoors. I use a BEC integral with the ESC Martin, the whole is in the line of a good airflow. I don't know what the generally accepted life of servo is, the Futaba examples I am using are about six years of age; maybe it is time to ditch them? That said, I have some Fleet servos of several years age that still work fine! Wondering also whether I should use a separate NiMh battery pack?
I experienced something new yesterday which pretty much wrote off my second electric powered Pulse XT60.
What happened is described below. Has anyone else had a similar experience please and know what the cause and/or fix might be?
I was enjoying my second flight of the day with the aircraft and practicing stall turns. I was lucky in that I was accompanied by an experienced club member who was able to witness the pattern of events and confirm it wasn’t down to me.
On the third stall-turn pull up, I thought I may have perceived a short delay between commanding up elevator and the model actually entering a climb. At the time, “Is it me?” was my first thought. All other control responses appeared fine. So I flew an orbit of the field and tried again. No, it wasn’t me, it did it again and with a slightly increased delay. On attempting an asap landing, I intermittently lost elevator authority and into the tree tops it went. I do not know whether I simultaneously lost aileron/rudder/engine, it was flying straight and level at the time and no deviation was required so no other stick movements were made.
A challenging tree-top recovery was aided by three fine club colleagues and a still functioning downward facing motor. This act rendered a largely intact fuselage but, sadly, the wings were written off. As power was still applied, I immediately exercised the elevator. No mechanical problems, no delay, working fine. I am at a bit of a loss to understand the chain of events. The club’s flying field is located in “Darkest Dorset”, well away from known radio frequency transmitters.
Radio gear was Futaba, Tx, T6J and Rx, R2006GS, and I’d left my mobile phone in my car. I had flown two other models earlier using the same Tx and not experienced any problems. Tx battery volts were well within spec. throughout.
Any helpful suggestions or clues would be very much appreciated; I have a slight preference to avoid a repeat!
Finally, I am devastated having severely damaged my second Pulse XT 60, it was my favoured model and I had hoped to take my BMFA “B” with it. I understand it is no longer in production so if anyone has a spare pair of wings they would be happy to part with, I would be most grateful. Please drop me a line and we can talk terms!
My first Pulse XT60? Hands up, my fault, wrong model set on transmitter………..
|Thread: Nimrod MR2 undercarriage|
Craig, presumably your Nimrod has flown by now, I would be grateful if you could give a report on how it all went. I have wanted to build and fly a model of it for many years and only recently discovered the plans,;of which I am now a proud owne! Like yourself, I had a professional association with the airframe. Any tips etc would be most appreciated.
|Thread: Fleet Control Systems|
I used Fleet equipment in my youth, 27MHz & 35MHz, before constructing my own set of the featured RCM&E 35MHz equipment - who remembers that? Never suffered any problems with any of it with one exception. The NiCad's provided with the 35MHz Fleet gear would not hold a proper charge; one duff cell maybe. A diversion off the M3 one day to Fleet sorted the problem. I called in, told Derek about it, there was no argument and he said "Fine". He then invited me to go upstairs in his shop, on my own, and help myself to a set of new ones; third cabinet on the left, second shelf etc. This I did and what an (unattended) Aladdin's Cave confronted me! We had not met before and he did not know me, I was amazed at the level of trust shown, a rare thing these days perhaps. The visit is something that sticks in my memory. That M3 diversion later became more of a routine but for all the good reasons. Different times perhaps.
|Thread: See if you can help me with this|
My take on David’s question 1 (For what it’s worth!).
Continuous power is measured in Watts; Volts x Amps in the basic sense. For batteries, we of course have a time factor, hours, because they are limited in the total amount of power they can supply.
For example, a 4000mAh 3s battery (~11.1V) stores a nominal 44400mWh power charge; 44.4Wh. Similarly, a 2000 mAh, 6S battery (~22.2V) at will also hold 44400mWh.
All electric motors have a maximum continuous power rating in Watts before the inevitable occurs; should they be asked to deliver more!
If a 630kV motor uses the 3S battery above, the maximum rpm would be expected to be around 7,000.
Using an in-line Watt meter, one chooses a propeller that will cause the motor, at max throttle, to draw the maximum power as specified in the suppliers guide – or maybe a little less to be on the safe side!
If a 6S LiPo was then substituted, the motor would then try to turn the same prop at around 14,000rpm and probably emit a little smoke before it got there – which it didn’t of course!
With the same Watt meter arrangement, one would chose a smaller prop that would present the motor with a reduced load/rpm yet retain the same max power consumption at max throttle, 14,000rpm in this example.
More S’s, smaller props! Q.E.D!
One point alluded to earlier is to bear in mind is that for the same power delivered through the cables, a higher voltage reduces the current that flows.
The advantages of reduced current is that there will be reduced volts losses at connectors (due to their contact resistance – V=IR etc. more volts for the motor, but not a lot necessarily) and the ESC will not need to be so “Ampy”! Also the desired maximum discharge current rating of the battery will be reduced, saving funds for the next project and perhaps extending the life of your battery too!
In the examples above, minimum Amp spec’s for a 550W motor would be approximately 25Amp for a 6S battery and 50Amp for a 3S battery; on the safe side, perhaps 30amp and 60Amp respectively.
So, in order to choose how many S’s provide optimum performance, do we now start a debate/thread about propeller efficiency with respect to rpm, diameter, pitch, etc, etc…….?!
|Thread: futaba T10J|
Mode 3 is a mirror image of Mode 2 re stick functionality.
Thanks CARPERFECT, will consider your offer. Re the change to Mode 3, presumably the throttle ratchet and sprung centering changeover requires a little surgery? How easy/simple is that would you know?
I have flown since returning post children using Futaba T6J. Have been thinking for awhile about catching up with developments and investing in a new Tx. The T10J looks attractive but I fly with Mode 3; left handed. The change to '3 on the T6J was simple enough. Does anyone know whether it is similarly simple on the T10J please?
|Thread: Glue advice please.|
Thanks guys, I'll mull over it.
|Thread: Scottish Aviation Twin Pioneer CC Mk 2|
I remember seeing one of those almost flying backward in a strong wind!
|Thread: Glue advice please.|
I have just removed a little grass from mother earth with my Flyingwings Raven. Fortunately, the only damage was a detached aileron. On this model, the ailerons are attached by a thin line of flexible glue. Does anyone know what glue this is please? The method of attachment may sound a little "basic" but it has served quite satisfactorily for many years; a great fun-plane.
|Thread: Additional battery?|
I'm with Allan Bennett. The DA solution may be okay under normal circumstances but should one pack develop a problem, the associated wiring/switches/Rx could suffer badly should one low internal impedance battery pass a high current to the faulty one; don't like it and would never use it. Probably okay most of the time though but I would regard it as a big-time problem waiting to happen. (MAD Dave CEng etc.)
|Thread: From where might I acquire a Pulse XT60?|
Oh dear, suffering from dyslexia now....
Slightly gobsmacked, the Amazon seller is listed as
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