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Member postings for MAD Dave

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: Wattmeter Quandry?
02/11/2019 00:01:17

Experimental error Simon? Suggest try again a couple more times to consider the range of results. Talk Sunday.

Thread: Design assistance request!
01/11/2019 22:51:08

Having got my 3D printer kit built and working successfully, I have used Tinkercad to design and print a few sundry items, even a made-to-measure battery tray/Rx mount for my "pre-loved" HK Spitfire. I am very pleased with the quality of the prints so far and have aspirations to use the printer for further modelling bits and pieces. As a start, I decided I would like to have a go at constructing a simple straight sided (trapezium) outline fin for my latest home build project – and have hit a brick wall. I am aware that a classically built up fin would probably be lighter but just wish to give it a go and see what I can achieve.

My status in the 3D print world is of course biased toward the inexperienced end of the spectrum, so, any tips and suggestions would be most appreciated.

Put simply, I have the root aerofoil and the tip aerofoil but I cannot see how to smoothly fill the space between them. I am quite able to position each aerofoil correctly in 3D space in software relative to each other but filling the space between them is my challenge. I am yet to come across the "secret button" or process.

I have had reasonable success with Tinkercad and have installed Fusion 360 on my pc. I am slowly working my way into '360.

As stated above, any help would be much appreciated.

Thread: Glue for PLA and PET-G
01/11/2019 22:10:36

Having got my 3D printer kit built and working successfully, I have used Tinkercad to design and print a few sundry items, even a made-to-measure battery tray/Rx mount for my "pre-loved" HK Spitfire. I am very pleased with the quality of the prints so far and have aspirations to use the printer for further modelling bits and pieces. As a start, I decided I would like to have a go at constructing a simple straight sided (trapezium) outline fin for my latest home build project – and have hit a brick wall. I am aware that a classically built up fin would probably be lighter but just wish to give it a go and see what I can achieve.

My status in the 3D print world is of course biased toward the inexperienced end of the spectrum, so, any tips and suggestions would be most appreciated.

Put simply, I have the root aerofoil and the tip aerofoil but I cannot see how to smoothly fill the space between them. I am quite able to position each aerofoil correctly in 3D space in software relative to each other but filling the space between them is my challenge. I am yet to come across the "secret button" or process.

I have had reasonable success with Tinkercad and have installed Fusion 360 on my pc. I am slowly working my way into '360.

As stated above, any help would be much appreciated.

Thread: Cheap Chinese Laser Cutter
27/09/2019 11:45:06

......which is the background as to why I was enquiring about laser "life" earlier in the thread

22/09/2019 19:22:10

Is there any clue to the life of the laser?

Thread: Glue for PLA and PET-G
25/08/2019 11:58:05

Many thanks for your inputs chaps.

I have yet to get my Prusa Mk3s kit out of its box, having stalled at the somewhat voluminous assembly instructions book! In the meantime, if anyone learns something significant re PLA/PET-G adhesive, please let me know via this thread.

Back to studying the assembly instructions...........

21/08/2019 14:04:48

Has anyone tried uv curing adhesive? 3D materials in particular.

21/08/2019 09:29:38

I have just ordered my (first!) 3D printer with a view, in part, to it contributing to my model builds; possibly even construction of whole models.

In the case of a "whole model", printed in pseudo-Airfix components and glued together to form the whole, I am at a slight loss to know what adhesive to use; PLA and PET-G in particular.

Does anyone out there have any practical experience and recommendation(s) please?

What I am particularly keen to avoid is the likes of this........... **LINK**

Thread: How to reduce voltage?
16/03/2019 14:38:53

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!

16/03/2019 13:20:19

Place some diodes in parallel to share the load, ie, heat. Recommend the same spec. devices.

Thread: 1/6 Westland Whirlwind
14/02/2019 18:15:12

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
10/02/2019 13:27:29

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?
08/02/2019 14:44:24

fao Piers - Wareham!

Thread: Latent Servo Response
12/01/2019 00:39:08

Thank you everyone for your thoughts, much for me to think about now....................... dont know

11/01/2019 17:13:47

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?

11/01/2019 11:29:41

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
08/12/2018 10:46:43

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
07/11/2018 23:16:58

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
29/08/2018 18:07:36

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
23/08/2018 22:13:39

Mode 3 is a mirror image of Mode 2 re stick functionality.

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