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Member postings for John Cole

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

Thread: John's little dolly
20/07/2009 17:27:38
Assembly
 
Slide one axle through its bearing and then put two scraps of silicone-rubber tube on it.  Slide the other axle through the other bearing and feed its end into the first bit of tube and then the second.  These two pieces of rubber hold the axles together – not super-securely but then the dolly is not going to fly!  Arrange so the two collets are about 1/8” clear of the bearings, with the silicone-rubber tube clear of them.
 
Go flying!>>
20/07/2009 17:26:03

BUILDING
 
Prepare the parts shown on the parts list.
 
The retaining pin assembly
 
Place the pin lengthwise on the ¾” piece and glue the two ¼” pieces either side.  Glue the ½” piece on top, sandwiching the pin.  When the glue is dry, wrap tape round the ends of the pin to stop it falling out in flight.  Place ¾” side face down on the inverted fuselage, and slide it back / forward so the wheels will be in the right place: hold one of the frame-arms with the V engaging the retaining pin; the front of the arm should be an inch or two in front of the wing leading-edge.  Mark the position of the pin-assembly and glue it in place.
 
Wheels and axles
 
Centre-drill the hubs to take the axles and place flat on a spacer (say a large nut or washer) so the end of the axle can poke through, and epoxy the axles into the hubs with ¼” protruding through the hub.  Keep the axles vertical while the epoxy cures.
 
Centre-drill the pot-lid wheels and drill 3 holes ¼” out from the centre for the fixing screws.  When the epoxy has cured, apply plastic glue (such as UHU Por) to the hubs, slide the pot-lids onto the axle protrusion and screw in place.  Put collets on each axle, about 1½” in from the wheels.
 
The frame
 
Place the two arms either side of the fuselage with the V engaging the pin, and with the open part of the V facing up.  Tape them to the fuselage.  Place the bearers across the fuselage, one just in front of the pin and the other lined up with the front of the arm.  Glue the bearers to the arms.  When the glue has set, reinforce the joints with balsa scraps. 
 
Drill holes in the legs for the bearings, to be a tight fit.  Insert the bearings and align them by poking an axle through.  This will be most accurate if the legs are held lined up parallel an inch or so apart (e.g. rubber-banded to a matchbox).  Apply glue to both sides of the bearing/leg joint, and let dry.  I used cyanoacrylate.
 
Glue the legs to the outside of the arms (I used PVA).  When dry, glue scrap balsa reinforcement to the inside-face of the legs both above and below the bearer.  When dry, chamfer the balsa at the top of the legs so they slide on to the fuselage easily.

Edited By John Cole on 20/07/2009 17:26:59

20/07/2009 17:22:51
I have an electric 40” span parkflier that has no undercarriage.  I decided it would be nice if it had wheels so it could take off.
 
The grass strip I fly from is not that smooth so it needed quite big wheels for low rolling resistance, and these would be a bit heavy for the small model.  So I decided to make a dolly.  I looked on the Forum but did not find anything that looked suitable for a small model flying from a grass strip.  So here is the simple two-wheel design I ended up with.  It has two key features: first, the dolly is “hooked” to the model and only releases as the model takes off; it will stay hooked to the model until then.  Second, the wheels are both rigidly fixed to the axle, which runs in bearings in the legs of the dolly.  So if one wheel turns then the other turns with it (by the same amount).  Provided the wheels are of identical diameter, they dolly will always (try to) run in a straight line.  Oh, and it is just made from scraps.
 
Hook the rear of the dolly over the retaining pin and slide the legs up the fuselage until the cross-wise bearers touch it.  Place on the strip facing the wind, and apply full up-elevator to stop the model nosing over.  Open the throttle until the model starts to roll forward, and ease off the elevator completely while increasing to full power.  Keep straight using the rudder if necessary (mine scarcely needs it) and apply up-elevator to take off.  The dolly releases when the model is a few inches off the strip.  Here's a photo.
 


Other photos, parts-list and diagrams are at: The dolly pix
 

Edited By John Cole on 20/07/2009 17:24:06

Thread: Battery tester/not......
20/07/2009 17:12:07
Even with the correct charger setting it might be a good idea to fast-charge with the battery pack out of the Tx.
Thread: Piwakawaka funfly
20/07/2009 17:07:41
Ray Huntley said he didn't want the plane going in the "unpressurised baggage compartment" .  I thought they were pressurised (to the same pressure as the cabin)! 
Thread: V-Trainer
20/07/2009 10:38:55
Mike: the most-common way to assign the sticks to channels for a 4-channel plane is:
Right stick: Up-down = elevator, Left-right = Aileron
Left stick: Up-down = throttle, Left-right = rudder.
This arrangement is called Mode 2. 
The controls on the right stck are as per a full-size plane's joystick.
 
The older arrangement still preferred by a few (Mode 1) is:
Right stick: Up-down = throttle, Left-right = Aileron
Left stick: Up-down =elevator, Left-right = rudder.
 
If at some stage you want the help of an instructor than he will need to fly the same mode as you, so I recommend you choose mode 2, as more instructors fly that way.
 
I expect you can re-assign the simulator controls to match this arrangement.  I can't follow what you mean about the controls on the Spektrum.
Thread: How do you seperate Dean's connectors?
20/07/2009 10:30:02
Doug: you didn't say: "Do not put the screwdriver between the pins, as that risks a serious short-circuit  which could cause the LiPo to catch fire".
Thread: LiPo Saver/cut off
20/07/2009 09:47:25
Why don't you contact Vapex: they are offering some larger cells which sound as if they are similar to the Instant cells.
Thread: Lipos
19/07/2009 14:14:19
4S 3000mAH £33.91 each.  GiantCod rules OK!
Thread: LiPo trouble
19/07/2009 13:58:28
A good LiPo will keep its charge for years, so you don't need to re-charge them immediately after use.  All that does is shorten the life of the LiPO: they lose capacity if stored fully-charged.  Only do a very-slight charge to bring them back up to about 3.75V/cell.
 
Measure the voltage of a brand-new LiPo and you'll find it's about 3.75V per cell: that's about 40% charged.  The manufacturers send them out like that for good reason!
Thread: LiPo Saver/cut off
19/07/2009 13:23:24
Modern NiMH cells have so much better performance (energy storage capacity)  than older ones that I'm not sure there's that much advantage in using LiPos in a boat.  The LiPo advantage of low self-discharge: you can get that in NiMH too nowadays. See the Instant cells at: Vapexcells
 
Thread: Decent parkfly required
19/07/2009 13:06:18
If you are still working towards your A then why not try a Flying Wings V-trainer (or mini-V)?  Flying Wings main page
If the field is a good size then the larger model is probably better.  OK so they're 3-channel / no ailerons, but they're easy to fly and hard to break.
Thread: How do you seperate Dean's connectors?
19/07/2009 12:02:52
Pushing a metal screwdriver blade BETWEEN the pins could of course short the LiPo, as the pins are live until the plug is extracted from the (LPo-connected) socket.  So I don't think that's an idea I would recommend.
19/07/2009 11:22:26
I wrap 1" masking tape round each half of the connector, so the tape covers the half-connector and goes 3/4" up the cable, and then I find they're easy to separate: the tape's easy to grip.  You can buy ribbed ones, but I find they're not that much better.  You can of course lubricate the blades (rub a pencil on them, leaves graphite behind) but using them a few times (plus taping them) means, for me, no problem.
Thread: Flight Simulators
19/07/2009 10:47:22
John S: Let's go back to the original question: Yes, FMS works perfectly well with a USB link to your Tx.  The USB "connectors" pick up the Tx frame pulses and convert them into a USB signal.  I bought one from China via Ebay for under £10 including postage, and it had connectors of various types including jack and Futaba-square.
 
But before that I used my Microsoft joystick, and for fixed-wing it's quite good for a start.  Rudder is on the twist-axis, but you soon get used to that.  The bigger problem is the lack of trims (particularly elevator), but you can "cheat" your way round that:  when you calibrate the sticks in FMS you have to put the sticks in the neutral position, but if you want to add Up-trim - put the stick with a little Down when it checks neutral.
 
Either way, all you do is tell FMS to find the joystick ,and then assign axes: which controls to which stick, whether they are reversed - and whether you want exponential.
 
You will see posts elsewhere that there are problems with Vista, because Vista comes (came?) without a certain .DLL, but you can add that.  I run both FMS 7 and FMS 8 on XP SP3 Home Edition.
 
FMS 8 adds windspeed and better flight dynamics and so is to be preferred.  However, FMS 8 comes with only a few models (but you can just copy across the FMS 7 ones).  Models written specifically FOR FMS 8 have some special characteristics, but I warn against importing lots of these: most of them use a standard .PAR file (which describes their aerodynamics), so they all look different but fly identically! And badly.  Modify your own .PAR file (it's easy) or PM me with your Email address and I'll send you one that I have modified and like.

Edited By John Cole on 19/07/2009 10:58:58

Thread: Using a seperate cell battery charger on a 4 pack Rx
18/07/2009 14:49:06
Whoops: to late to edit it.  I meant 44 ohms of course.  At 70 mA it's about 14 ohms per volt, so 42 (=/= 44) for 3 V and 112 (=/= 120) for 8V.
18/07/2009 13:14:49
No: you'll get perfectly OK readings even if you use fully-charged batteries.
 
If you want to drop 3V at 70 mA (13V campervan battery to 10V to charge a Tx NiMH) then a 440 ohm resistor would be about right.  A fuse is not a bad idea.  Yes a low-wattage resistor will be fine, but you could instead use odds n ends like torch bulbs: probably two in parallel would be OK for the Rx pack (depending on voltage and wattage).  Just wire them up and see what resistance you get.
18/07/2009 10:36:43
Two possibilities: your charger can charge just one cell so it doesn't have slots wired in series to charge two cells at a time (the usual arrangement), or you have wrong-polarity protection diodes: do the beep check again but this time for each of the 16 steps do them twice (probes reversed the second time).  Depending on the sensitivity of your meter you may be able to detect the cross-wiring.  If that doesn't work then put 4 cells in the charger and set it charging, and measure the tag-tag voltage for all 16 combinations.  Those that show near-zero are cross-wired or isolated. You may even find a pair showing 5.6V - which is what you want.
 
On my charger the slots A1 and B2 are paired for charging two cells, and C3 / D4 also.  This pairing is marked on the charger. 1 and B are wired together as are 4 and C, so when powered up with 4 cells in I see 2.8V across 2 and A , 1.4V across 1-A and 2-B and zero across 1-B.  Similarly on the other side except 2.8 across3-D, 1.4 3C and 4D, and zero across 4C.
 
You might consider using a simple voltage-drop resistor instead!  If your camper battery is at about 13V, and your on-charge NiMH battery is at about 5V there's an excess of 8V.  If you want constant-current of 70mA then you would want a 120 ohm load in series.
17/07/2009 17:56:10
These chargers normally charge pairs of cells in series, but yours may optionally charge 4 cells in series when on that setting..
 
When you put cells into the charger, which terminals do the cells connect: I would expect from your description that they are:
cell 1: A to 1
cell 2: B to 2
cell 3: C to 3
cell 4: D to 4
 
but you may mean something different.
 
I have found several UNIROSS Encore chargers (UNIROSS is the make I think with Encore being the model-group), but can't find one called 0267.  Any more (short) numbers on it?  If not, does it have a switch for 2 / 4 cells, or does it auto-detect that?
 
Using my connections above, I would assume that for 2-cell charging you just put cells into the cell-1 and cell-2 slots.  In that case, the terminals 1 and B would be wired together (or possibly A and 2) and the two cells would be charged in series with 2.8 volts across 2 and A (or 1 and B if it's the other way round).
 
Similarly for the other pair of cells.  It's not clear if the first and second pair are interconnected.
 
With the power off and using the Beep on your meter (to check connection, a setting on the Resistance group of your digital multimeter) and with the switch set to 4-cell charging, test which of these gives a beep:
 
a to 1, to 2, to 3, to 4
b to 1 ...
 
that is 16 tests in all.  That will show which of my two cases applies, and whether the pairs are cross connected.  That should then tell me where you can pick up 5.6 volts (the charge voltage for 4 cells in series).
 
 
 

Edited By John Cole on 17/07/2009 17:57:13

Thread: Cyanoacrylate safety
17/07/2009 16:26:06
Myron: I think you probably could it you really wanted to, but it wouldn't taste the same.
 
Seriously though, hardened CA is quite brittle and after 24 hours most of it has just disappeared from my fingers.  As I'm sure you know, CA was developed for emergency wound-closure on the batlefield (which is why modellers' packs are marked "Not Sterile" - to dissuade you from using it to "heal" scalpel-cuts -but it works for me), but although it glues flesh nicely, the oil coming out of your skin makes the CA detach from it.
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