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Member postings for Malcolm Frary

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

Thread: help - 1/250 scale Yamato
27/11/2020 11:24:10

The single 280 will be enough to see the propellers turn and the model move, and not much more. Probably enough for the model designers to realise their intention in the circumstances that they imagined at the time. Running the numbers, 150,000 SHP on the real thing gives about 8 Watts out of the motor at scale, probably needing about 15 Watts of power into the motor(s). Way too much for a single 280, well within the capabilities of a group of 385s running on reduced voltage if the intention is to move a 10 lb model at a bit over 3 feet per second.

Cavitation is only likely if the kit props are poor - plastic kit moulded ones can have very thick blades which create more turbulence than drive. Most "cavitation" on models is actually aeration - air being sucked down from the surface. Model battleship props are likely to be far too deep to be affected.

Thread: help with rc/control
26/11/2020 09:03:49

The two wires probably had a small slide switch on the end, used to switch the control part of the ESC on and off. If a previous owner didn't feel the need for it, or if it died from old age then shorting the bared ends of the two leads together would result in the ESC being on all the time that it had power.

Thread: viper marine 15 bec s/c
24/11/2020 09:48:30

Zero experience with Ace Commander gear, but the last time I saw this the transmitter had a well hidden little switch marked "mix" which he had managed to slide. That was on a Joysway lunchbox transmitter.

The side slider usually just operates to swing the position of the pot a bit one way or the other to mover the center position. Sliding that will move the deadband, Moving it far enough will cause the ESC to tell the motor to start turning.

Thread: help - 1/250 scale Yamato
23/11/2020 09:58:37

I would go for 4 of 385 motors, but it is well to remember that you can run them on a lower voltage than the max stated on the label. 4 brushless motors will probably mean 4 ESCs, with brushed motors you have the choice of how many ESCs you fit. One driving them all, 2, each driving a pair, one per motor. You also get plenty of choice of how much individual control you get. 15 volt motors on 6 volts should be about right.

Gearboxes supplied in plastic kits have a reputation for being noisy. A large plastic hull tends to act as a loudspeaker cabinet, so eliminating a dodgy gearbox with direct drives tends to be a lot quieter.

Not familiar with the details of this kit and its rudder area, but if it can be arranged with a good enough rudder shaft tube, yes.  If not, a rudder is one of the simpler things to knock up out of brass rod, sheet and tube.

Edited By Malcolm Frary on 23/11/2020 10:06:09

Thread: 1:24 RRS Discovery
09/11/2020 10:11:11

Ashley has already given the correct answer to the waterproofing problem. Just simple resin or varnish won't work because the hull structure will "work" and re-open the holes. The cloth prevents this.

Back in the day it probably used SLA as a battery. While SLA is great as ballast, it has the drawback that such batteries put the center of gravity where they want it, not where you want it. Usually too high, often at the wrong point along the hull.

You get the same voltage capacity for much less weight, and in a more managable shape, using NiMh. The weight saving can be made up by fitting lead as low as possible inside, and/or as an extrenal strip along the keel.

I expect that it is not intended to operate under sail?

Thread: Action P94 dual esc/mixer
02/11/2020 10:21:58

Component Shop reckon they are in stock.

https://www.componentshop.co.uk/p94-dual-esc-and-mixer-2-x-20-amps.html

Thread: LED on RX voltage
02/11/2020 10:18:38

A switch should either be an open circuit thus zero current when it is "off", or zero resistance when it is "on". It will offer no volts to the load when off, or the full supply voltage when on.

A mechanical switch like you find in a switcher with a relay has contacts that act just like any other switch. They don't care which side they switch, ground or positive, but have the bulk of the relay. With relay contacts, there is the option of switching any voltage as required.

Electronic switches, you need to read the instructions, or at least have clues on the case. They are usually designed so that they switch either the ground line or the positive line, and it is as well to know which. Less bulk than a relay, but more picky about how they can be used.

Red and green LEDs usually in the range of about 10-20mA, so no real worries about consumption there. White LEDs tend to be thirstier plus they need more volts, so no option on 5 volts to form daisy chains.

Thread: Unable to view the magazine online
27/10/2020 14:02:59

Silly question - have the settings been tweaked on both? Just asking as the proud owner of a similar T shirt. I also manage to create some confusion for myself when using the "wrong" browser.

Thread: wood breaking
14/10/2020 09:27:50

Enough heat at the time of doing the bending makes the wood plastic enugh to bend. It should also make the glue holding plies together soft enough to let the plies slide past each other, reducing the compression and streching.

Of course, that kind of heat does the same job on fingers, so Ashley's stout leather gloves help.

Thread: making rudders
04/10/2020 09:57:13

I have used Neil's method for about the length of time that I have built model boats. Simple and effective. A later thought was to not bend the rod, just file a flat on each side where it is going inside the blade. When epoxied into place, works just as well. Idea grabbed when replacing a Chinese "stainless" rod on a plastic rudder on a yacht.

Smaller rudders, the brass plate method, either using a slot in the end of a 5mm rod, or, using a longer 3mm rod with a flat where the blade is to butt join to the rod. I have been told many times that that can't work with reglaular soft solder. If I had been told that 30 years ago, I might not have done it that way. A 3mm rod has the advantage that tiller arms are cheap - a brass arm ready to accept a hole at the right distance and having a 3mm hole plus a brass screw is cheaply available, free with any dead electrical appliance. It's called a "13 Amp Plug". Choice of 2 arms. Sometimes needs a bit of filing to thin down to make threading a link wire through.

Thread: Returning modeller
24/09/2020 22:09:22

The important rule is that anything that passes power on should be shrouded and will probably be the receptical, any connection that collects power will be a blade. Same as domestic wiring - you dont want to be waving live power around where it can do harm. It doesn't matter whether it is the positive or negative side - it is whether voltage is being presented or collected.

Thread: ESC ratings for brushed motors.
11/09/2020 09:27:46

The nce thing about brushed motors is that you don't need an ESC to check what current they take. Just get a bag of assorted fuses and connect them to the battery under load. Take the lowest value fuse that doesn't blow, pick an ESC of a higher current rating (preferably start at fuse + 50%) and it will work. If using a meter to check the current, start at 50% more than the reading.

Thread: Controlling bow thruster and propulsion motor
09/09/2020 21:45:31

What Dave said. The BECs in the ESCs power the internal parts of their ESC and, via the red wire, the receiver and anything plugged into the receiver. Two BECs into one power rail might not play nice, so disconnect one.

Both small switches will need to be "ON" for the circuits to work, but both need to be "OFF" when the system is powered down if the battery remains connected. A good idea is to mount them both together so that you can see that both are off. I've been caught by a black switch hiding in a dark recess resulting in a mysteriously flat battery before.

Thread: Hobby Engine “Richardson” tug boat upgrade
07/09/2020 14:42:37

Probably one or two more screws hiding under deck fittings.

If hunting on tinterweb, it might also be known as "Southampton". Probably a few rebuilds around, hopefully by people who have found the hidden screws.

If only the sailboat crowd see your query and ignore it, it might be better posting in a more general area like "all things..." or "beginners".

Thread: Returning modeller
02/09/2020 09:43:43

If a 10A fuse is being blown on a regular basis, it probably means that more current is being drawn than the 15A ESC can safely handle. A lower rating is needed for a fuse than the ESC involved because fuses are not instant acting. The length of high current time that it takes for a fuse to blow can be critical for the electronic bits involved. The answer is either a less demanding load on the motor (less prop diameter, typically) that will demand less current and/or a meatier ESC that can handle what is demanded.

A down and dirty method of figuring what ESC current rating is needed is to do empirical tests using fuses instead of an ESC. Fire it up under load (i.e. prop in water) and figure out the lowest value fuse that doesn't blow. Or use a meter to get the actual number, but most multimeters stop at 10A. Multiply that by 1.5, look for the next rating ESC above that figure. Avoid ESCs that claim 320A and don't have a recognised makers brand name.

Thread: Motors/prop for model warship
01/09/2020 21:47:05

The much quoted rule of thumb for sussing out a combination of motor and prop is "motor can no less than prop diameter, prop should have fewer blades than the motor has poles." Not scientific, but it works. Having the precise definition of a brushless motor is great if what is actually wanted, or needed, is known.

A very common question that crops up is "Why is my motor too hot to touch after only a few minutes?" The answer is always "There is too much prop". If going for a 360, go for a smaller prop with fewer blades. A 385 with a 30mm 3 blade prop works well and will not melt the solder off the terminals (yes, seen it done)

Most of the 385s that turn up in model shops say 6-15 volts on the label, running one on half to 3/4 the max gives the right performance for a surprising range of models.

31/08/2020 11:14:56

The main reason that the one I mentioned earlier wound up shorter was the free wood panel size. The reason for it being that bit deeper was that in that magazine issue there were two plans. One for a retro Bowman look-alike launch, the other the Quickstep.

I started on the launch and decided that I would rapidly get bored with it. A bit of pencil work, a few bits missed off and there was a slightly shorter, wider and deeper "frigate". It got called "Troutbridge". Despite the lack of any actual prototype, it didn't stop the occasional passer by claiming to have served on one, or something very similar. At least, until they got a close view. They were all polite enough to not mention the missing rack of torpedo tubes.

A boat this size will work well with a 385 on around 3/4 the volts it says on its label. A much smaller 280 will be working far too hard. A longer shaft lets you position the inboard end higher, hopefully above the water line, while keeping the angle shallow.

30/08/2020 09:05:02

My first go at building from a plan was HMS Quickstep, probably a GG plan. A few changes were made as it was built from ply panels recovered from a dead kitchen door. It ened up a bit shorter (missed out a set of torpedo tubes) and a bit deeper (about 1/2" which heped stability and payload. The ply probably helped make it strong enough to minimise bank damage.

With a free running boat, you don't get to choose which bit of bank its going to slam into. You have to guess and get there first. Remote steering helps. Getting a speed control as well was a revelation.

Thread: Action P44 Twinlatch switcher
24/08/2020 08:59:40

Small relays can operate big relays, but its all extra weight and volume and complexity - extra battery or bigger battery is better. More run time plus less chance of it not working when needed.

Thread: Smoke unit
23/08/2020 17:09:51

Everybody would like a smoke unit that gives black smoke. Nodody makes one. Given that generally the black particles that smoke comprises are usually considered carcinogens, nodody is likely to.

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