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Member postings for Dickw

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

Thread: Writing on electric motors
13/09/2014 18:00:07

Indeed Aveox were always highly regarded and did a lot of the brushless pioneering work for us modellers. Losing a magnet is still possible, but at much higher rpms these days with the improvement in glues, and most good inrunner motors also have the rotors kevlar wrapped to help keep the magnets on at operational speeds in the 60,000 to 70,000 rpm range.

Getting back to the subject, an example of "numbers on motors" can be seen here on a geared inrunner **LINK**

In this case 2035 is the dimensions of the rotor, 2100 is the kV, and 2D tells me it is a 2 turn Delta wind.

The rotor dimensions give me an idea of the power handling capacity relative to other motors, the kV tells me what rpm I can expect on a given battery, and the 2D adds very little but sounds impressive!

Dick

13/09/2014 17:10:20
Posted by Peter Beeney on 13/09/2014 16:53:54:

...................... An inrunner, with the windings on the revolving rotor inside the stationary magnets does need to be made to withstand some considerable stresses however, they are capable of some very high speeds.

......................PB

Just for clarification for those unfamiliar with that type of motor, the last "inrunner" I saw in which the coils rotated had brushes.

All the brushless inrunners these days have the magnets attached to the shaft and spinning within fixed coils, and yes they are capable of very high speeds - I have seen 80,000 rpm on a data logger when the prop came off.

Dick

Edited By Dickw on 13/09/2014 17:26:24

Thread: JP EnErGy 45A What am I doing wrong
31/08/2014 10:00:03

The beep comes from the motor not the ESC and if the shudder is in time with the beep it is probably just the ESC pulsing the motor to make the sound.

I don't know that particular ESC, but some ESCs beep slowly(~ once a second) if they don't have a throttle signal at power up. I would try plugging a servo into your throttle channel and see how that moves to confirm that is not the problem. Might also be worth checking the ESC signal lead/plug for breaks.

They can also or beep a bit faster if the throttle signal is too high at start up, so check travels and trim settings are as low as possible in the Tx.

Other then that I am out of ideas.

Dick

Edited By Dickw on 31/08/2014 10:00:56

Thread: Carbon fibre airframe
25/08/2014 14:39:33

Well I do have a few all moulded carbon fibre planes (wings and fuselage) and it is possible to use 2.4 GHz with care. However you do need to get the aerials outside of the carbon and do a good "all angles" range check to ensure the signal is not degraded by the "shadow" of the carbon from certain directions. Picture attached of one of my aerial installations.

Dick

aerial support.jpg

Edited By Dickw on 25/08/2014 14:40:18

25/08/2014 13:11:25
Posted by Jamie sawyer on 25/08/2014 11:40:57:
If I was to opt for epoxy and glass clothing wings what weight of woven cloth should I be using....? about 80 grms at a guess but it is a guess lol

I have used 80 grms cloth when covering directly over blue foam, and that give a reasonable surface. For covering over a balsa surface I often use 40 grms glass cloth.

Heavier cloth gives more torsional rigidity, a more 'ding' proof surface, and more weight. It all depends on what you are looking for.

Dick

25/08/2014 09:59:08

Tissue usually has the fibres in a random mat arrangement as opposed to cloth which is woven with the fibres in an organised uniform arrangement, so as a result carbon fibre tissue is not as strong as carbon fibre cloth. Most high sterngth moulded gliders use light weight carbon fibre cloth for moulding wing surfaces and spar webs, with carbon fibre tow (like string) used for spars.

Rather than carbon fibre tissue I would use glass cloth for covering wings (unless you really do need the sterngth of carbon cloth) as it doesn't have the same issue with 2.4 GHz signals.

Also remember that it is the cloth that give the strength and the glue that gives the weight, so use as litltle epoxy as you can get away with. Its a good idea to seal wood or foam first before using epoxy so it doesn't soak up too much.

Carbon doesn't flex as much as balsa, so once you start adding it as reinforcement to spars you have to add enough to take all the load.

Dick

Thread: Trial results and a question about timing
24/08/2014 18:08:08

Spikey

Your latest post does clarify the data, but Simon’s comments about motor size and weight are still valid. kV is just one indicator of the potential motor performance and motors of the same kV can vary a lot.

For example higher weight suggests more copper in the windings and so possibly lower winding resistance which means more watts for the same volts:- i.e. from Ohms law, watts = V2/R so the lower the resistance the higher the watts.

Other testing issues to check, are what is the rpm, was the battery volts dropping between tests as the battery discharges, is the battery warming up (lowers the battery resistance and increases volts). All of these need checking if you are trying to compare motors.

Dick

Thread: National Model Flying Centre
22/08/2014 17:07:01
Posted by Gary Manuel on 22/08/2014 15:47:45:

...........I know that I skipped these two questions because the answer I would have selected wasn't an option. i.e. £0.00

................

Interesting use of statistics to get the required results!

I don’t understand.

From the BMFA website: -“Question logic was used throughout the survey. For example if a respondent indicated they would be prepared to support a centre but not accept a subscription increase they were then not asked how much of a subscription increase they would be prepared to pay.”

Anyone who got as far as Q4 must have already told the BMFA that they supported a NMFC, so it appears that you said that you did.

Presumably you answered Q3 by saying that you would not accept an increase in subs, and Q7 by selecting “neither a donation nor a bequest”. If this assumption is correct you would not have been asked Q4 or Q8 – i.e. your vote for £0.00 increase was already recorded.

OR

Did you answer that you would accept an increase in subs and make a donation, and then deliberately skip Q4 and Q8 because you couldn’t decide how much?

Dick

21/08/2014 10:04:33
Posted by Dave Hopkin on 21/08/2014 09:19:33:

.............................................................

As for getting actively involved... where is the information - if its on the web site, its well hidden

 

Who is my area rep, I have no idea! How do I find out.........

 

Sorry but all this SHOULD be on the web site and easy to find....

........................

 

 

Have a look on the website for Areas - I found this page **LINK**

Seems to have all the contact details for the area I am in.

Dick

Edited By Dickw on 21/08/2014 10:06:18

Edited By Dickw on 21/08/2014 10:06:54

Thread: Why Dihedral on 3ch Models?
18/08/2014 12:24:00

I am no aerodynamicist, so its’ probably a case of the blind leading the blind, but I find that looking at extreme examples helps me understand some things.

In this case a wing with dihedral travelling forwards has the airflow affecting both wing halves the same, and an elevator induced pitch change will change the angle of attack.

Now keep the wing level and still travelling the same direction but turn it 90 degrees so it is sideways on to the airflow. The airflow is now hitting the bottom of the forward wing half and the top of the rear wing half. i.e the angle of attack of the airfoil relative to the airflow is completely different for the two wing halves without any pitch change. The ultimate in sideslip.

You would obviously never see this much yaw induced sideslip in normal flight, but even a few degrees would start to produce this effect.

I am sure any real aerodynamicist is now having hysterics at my explanation laugh.

Dick

18/08/2014 09:27:28

Well Fig 2 in that link is exactly what I was trying (obviously badly!) to described in my post.

So much easier to understand with a picture.

Dick

17/08/2014 18:24:38
Posted by David Cooke 1 on 17/08/2014 17:27:48:

Ah - yes , I remember - it produces a higher angle of attack. I'm struggling to visualize this with my wing in hand. I don't see how the angle of attack changes. You would need to pitch the plane up to change the angle of attack.

When the plane yaws because of rudder input, the angle of attack I don't see changes in the horizontal axis.

Stop thinking about the angle of attack in terms of geometry and start thinking about it as being relative to airflow.

Hold the wing at eye level looking straight at the LE in the centre – like you are the air heading towards it. Both wing halves should look the same – i.e. will have the same angle of attack.

Now turn the wing 45 degrees one way as if the plane is yawing with rudder input. You should now be seeing more of the bottom surface of one half and the top surface of the other half. That is an exaggerated view of what is happening, but it should help understand why the airflow is approaching the wing halves at different angles so the angle of attack relative to airflow is different.

 

Dick

Edited By Dickw on 17/08/2014 18:25:34

Thread: National Model Flying Centre
15/08/2014 15:15:34
Posted by Biggles' Elder Brother - Moderator on 15/08/2014 14:17:37:

...............................................But fear not - I am in the process of making just such a request to BMFA - and then I will know. And I will hopefully understand all sorts of new things like the relationship between the BMFA and the SMAE and the power of members to call EGM's etc. - and I'll make it public -....................................

 

Look forward to your comments when you have read it.

 

Dick

Edited By Dickw on 15/08/2014 15:16:36

15/08/2014 12:45:02

I have no particular interest in a National Model Flying Centre, and don’t really care one way or the other, but I do think there is a lot of hot air being spouted in this discussion. As far as I can see all the BMFA has done is ask its members if they are interested in such a centre and for some idea of how much, if anything, they would be willing to pay for it.

Judging by a majority of the 99 posts so far you would have thought the BMFA had for ulterior motives hidden that question where no one could find it, whereas in fact they published the existence of the survey several time in a magazine that they post to all members, and even extended the deadline to try and get a better response. What else do you want – personal phone calls from the chairman?

Perhaps internet forums?

Well they could have put it on here and reached the 35 people who have bothered to join in this discussion so far. How many other forums should they try to get the message across.

 

I don’t know if the BMFA survey can be said to be representative of anything, but it is probably the best current information they have. I assume they will now carry out some sort of feasibility study which may result in some more detailed proposals to be put to the membership. If people are really against it that gives them time to get like minded people elected to the BMFA council to squash it. That shouldn’t be difficult, but it does mean actually doing something.

 

NOTES

I stopped buying model magazines many years ago because I found nothing of interest in them, but I do read the BMFA mag because it comes through the door anyway – and no, I don’t fly Free Flight smiley.

 

The ‘BMFA’ and ‘SMAE Ltd’ are the same thing, the BMFA is just a public name they use to better explain what they are about (as has been explained many times over the last decade or so). If sending a SAE to get a copy of the constitution is a major obstacle then you are obviously not that interested.

 

Rant over.

 

Dick

Edited By Dickw on 15/08/2014 12:48:14

Thread: Clubs in Bedfordshire
08/08/2014 18:07:16

Kris

As you are in Luton why not go to the Offley field tomorrow (Saturday) afternoon and have a look and chat to anyone there. Entrance is 400m up the lane next to the Red Lion. Weather permitting there should be a few flying who are always ready to make vistors welcome.

Weather not permitting they will probably be IN the Red Lion, just ask at the bar for the model club smiley.

Dick

Edited By Dickw on 08/08/2014 18:08:59

Edited By Dickw on 08/08/2014 18:09:40

08/08/2014 14:36:16

I fly with the LDMAS and can thoroughly recommend it. as a friendly club.> >

>Plenty of info on their website:- >**LINK** >and I imagine a response to a contact would be fairly prompt.>

Dick

Thread: Have I killed a second ESC?
11/07/2014 22:41:37

The programming cards I have used in the past usually need the main battery connected to power up the ESC before they will work. If you are only using the Rx battery that could be the reason, as the Rx battery would not power up the ESC. Try just main battery and programming card.

Just in case you haven't already done it, it's a good idea to remove the prop while playing about with the ESC programming.

Dick

Thread: arials and carbon fibre
05/07/2014 14:23:59

As Tim said, if it is a full carbon fibre fuselage you will need to get the last 30mm of the aerials outside and preferably support them somehow, for example see attached pic.

Otherwise just try and make sure the aerials (or at least one of them) have a clear line of sight to the Tx, without carbon in the way, at all attitudes of the model.

A good range check will soon confirm if you have got it right or not.

Dick

aerial support.jpg

Edited By Dickw on 05/07/2014 14:24:53

Edited By Dickw on 05/07/2014 14:25:39

Thread: LiPo. RX Battery
02/07/2014 13:20:03

I leave mine in the plane as well. and charge them in there.

With a tight squeeze down a narrow glider fuselage removing the battery/Rx/switch "brick" takes sevaral minutes, and getting them back in has been known to take 15 minutes of swearing to get the aerials back in the external guides on the carbon fuselage ones.

Dick

Thread: Scorpion Backup Guard
14/06/2014 17:38:02

Hi Gordon

It was in flight failure I was thinking about, so yes with the normal BEC set at 6v and the backup guard at 5v, I guess an alarm at e.g. 5.2v would tell me if the normal BEC supply had failed in flight.

Interesting device and worth thinking about.

Dick

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