Landships II

Rectalgia · Legend

BlueprintBox

Paul Bonnett · Hero

Ever found r/c plans for a Mk1 anywhere ? Something I've always fancied !
Paul

TinCanTadpole · Legend

I'm interested in r/c tanks myself, though probably a later mark or something French or American. Did you have a particular scale in mind, Paul?

Paul Bonnett · Hero

Having recently seen a 1/35 FT17 r/c and with working turret and suspension I am thinking along the lines of 1/16 for a complete scratchbuild or maybe some very serious work on an Emhar 1/35. Will all depend on my level of sanity !
Paul

LincolnTanker · Commander in Chief

Paul Bonnett wrote:
Having recently seen a 1/35 FT17 r/c and with working turret and suspension I am thinking along the lines of 1/16 for a complete scratchbuild or maybe some very serious work on an Emhar 1/35. Will all depend on my level of sanity !
Paul

Wouldn't plasticating the 1/25 paper models save a great deal of work.

GPM Renault FT :- �http://www.papermodels.pl/index.php?action=profile;area=showposts;u=26

�

added this link�http://www.kartonbau.de/forum/index.php?page=Thread&threadID=12124&pageNo=3

-- Edited by LincolnTanker on Thursday 16th of February 2012 02:37:09 PM

TinCanTadpole · Legend

LincolnTanker wrote:
Paul Bonnett wrote:
Having recently seen a 1/35 FT17 r/c and with working turret and suspension I am thinking along the lines of 1/16 for a complete scratchbuild or maybe some very serious work on an Emhar 1/35. Will all depend on my level of sanity !
Paul
Wouldn't plasticating the 1/25 paper models save a great deal of work.
-- Edited by LincolnTanker on Thursday 16th of February 2012 02:37:09 PM

�Erm...I'm tempted to say no; the amount of work in the tracks of that FT alone would be mind boggling. I presume you mean laminating when you say 'plasticating'?

Would be interesting to think about, nonetheless.

�

Paul - 1/16th? That was the scale I had in mind when I first started thinking about an r/c tank last year, although the size of a MkIV tadpole at that scale (67.5cm) has made me think about something smaller; I've been drawn towards 1/20th or 1/18th as scales hopefully suitable to build anything from a Ford M1918 to a MkVIII* without small tanks being too small for r/c or large tanks being too long.

TinCanTadpole · Legend

Forgot to say...

If you're thinking of converting an Emhar 1/35 to radio, Paul, why not try asking member BC312 (Chris, I think) how he managed it with his 1/35 MkV.

Also, if you can get some Model Cellar individual link tracks (see Max's entries on Scratchbuilding Model Tank Tracks thread), it might help with the perennial problem of tracks.

LincolnTanker · Commander in Chief

By plasticising I meant using the card as templates to mark in pencil on plasticard sprayed with grey undercoat and then cut out.

The track could be a problem but should be castable from a plasticard fabrication, at least there are not as many links as a MarkIV has.

MK1 Nut · Hero

Hi,

If you're building small then I have seen tiny models radio controlled by using servos as the drive system.

There are servos of all sizes and torque, some with metal gears. Look at this link for how to make a servo into a drive motor... Link�Basically a servo is at its heart a geared motor with its own speed control.

Not done anything like this myself but I have seen small boats and even a tiny submarine built this way.

Helen x

I just noticed that is a computer cotrolled version, but the conversion of the servo is the same, just the servos plug into the receiver as normal.

-- Edited by MK1 Nut on Friday 17th of February 2012 06:50:04 PM

MK1 Nut · Hero

Nope not bored me :)

How about this...

P94 DUAL ESC AND MIXER 2 x 20

� 79.00 (P94 Lite � 76.00) Incl VAT

and...

950D1481 (4.5v - 15v) WITH RE 385 MOTOR. RATIO 148:1

and...

Timing Pulleys and Timing Belts

-- Edited by MK1 Nut on Friday 17th of February 2012 10:09:27 PM

TinCanTadpole · Legend

Hmm - yep, it might be easier that way, and I agree that casting is the best way for tracks just now (until rapid prototypers become available en masse at low prices), although I for one have never worked with resin - not that that is a problem until I actually have time/funds for such a project.

By my count FT has just 32 links per track (I count links, not rivets

), but think of doing a tadpole with 117 per side!

Since we're on the subject of radio control, can anyone help me regarding how one connects things up for two motor drive with electronic speed control? I understand a mixing unit is used to blend the signals from throttle and steering, but whether this demands two ESC units or not I don't know.
Also, in motor choice, how useful are the max efficiency rpm/current/torque figures in telling me how the motor will perform in use? It obviously depends on model weight, gearing, etc, but I'm getting the impression from the torque figures that the strong gearing down necessary for WW1 tanks means that a smaller, low drain motor can be chosen without imposing too much load and pushing the motor towards the current-hungry stall point. I'm concerned about battery endurance, as I had a 1/10th r/c truck in my teens, with a 540 size motor rated at 6.25A, which flattened the battery pack (admittedly only a 1400mAh) in no time. So really, I'd prefer to keep the drain below 5A at most, under 3A if possible, so that the running time is worthwhile.

TinCanTadpole · Legend

Thanks for your reply Helen, it'll be worth bearing in mind if I try anything titchy; what I was thinking about was something of a more reasonable size, maybe 1/20 or 1/18 scale. I was looking at motors around 260/280 size if I chose a small tank like an FT or M1918, heading up to 380/400, even 480 for a Mk tank. That said, I have come across a 540 that draws less than 3A at max efficiency on a 12v supply; the torque value doesn't sound that much for a 540 motor, but geared down for a Mk tank I think it could generate 2-3Nm of torque, which is surely huge for a model?

Essentially, for an r/c tank you can use one motor plus differential and brakes - the diff may be awkward, but installing radio would be no different from an r/c car. You could also forgo the diff and use two clutches to control steering.

Alternatively, you install two motors, which is what manufacturers seem to do. With two motors, to steer you either need to have each track controlled by a separate radio channel, so that you only need to change the input to the appropriate stick on the transmitter, or you control throttle for both tracks with one stick and somehow arrange for another channel to override the throttle signal to one of the motors, slowing or stopping it.

This latter case is my preferred option, as it is suitable for two-channel radio transmitters; controlling each track separately really needs a four-channel transmitter, so that you have two fore/aft stick functions instead of one plus a side-side stick. I think you'd also need two speed controllers, which would be pricey, and it's trickier to find an ESC that is suitable for smaller motors.

Have I bored you all yet? � yawn

TinCanTadpole · Legend

Been doing a bit of searching, it seems the mixing business is very simple - got my first pointers on an RC robot website, of all things; apparently all you do is plug the two input leads from the mixer into the appropriate channels on the receiver, then plug one output into an ESC for motor 1, and the other into an ESC for motor 2. Alternatively, if your radio allows, you can do the mixing in the transmitter. Sounds straightforward enough.

MFA Como drills has some interesting stuff - that's where I found the 540 motor I mentioned earlier that seems to have a low drain.
The P94 Lite sounds good; a bit more expensive than using separate units from MTroniks, but it seems a nice compact package. Thanks for your sleuthing!

BTW, did you have anything in mind with the pulleys? Gearing down, or final drive in a Mk tank's track horns? I was thinking of plastic roller chain for the latter - it's available in 3.117, 3.747, 6.35, 9.525 and 12.7mm pitches, which would suit a wide variety of scales, but quickly gets chunky in the larger sizes, so it wouldn't really be suitable as a basis for tracks.

Your suggestion, Helen, of using servos as drive motors is really appealing now...if only I could make up my mind which tank to choose!

LincolnTanker · Commander in Chief

�

I would use brushless motors, they have better low speed torque, should be easier to have the tank crawl.Brushless motors have a Kv rating, ie 1400Kv that is the revs per volt so 10volts woould give 14000rpm, keep that figure low to help gearing, worm gears work well in tanks

This is the sort of thing to look for available from most RC modelshops -�http://www.brchobbies.co.uk/?page=shop&category=31&catName=Motor%2FESC+Combo+Sets

�

Get a 2.4GHz RC that can be used mode 1 or mode 2 that camn be setup so a speedcontrol can be used on both sprung centre vertical sticks

TinCanTadpole · Legend

I agree that 2.4GHz is the way forward - no crystals needed and no unintended signals taking over your model! They seem to require less power too, which is a bonus, and only need a short aerial rather than a metre-long device. As well as that, non-brand-name radios with 4-6 channels can be bought for as little as �40-55; they're not full-range sets, so have a recommended max of 100m range in use, but that's more than enough.

I personally would only want to use the vertical axis on both sticks if I were to model something like a St.Chamond, which can be pirouetted on it's own axis by reversing one track; for other tanks, I'd prefer to have throttle on one stick, steering on t'other, so that no unrealistic pirouettes are possible. I also remember from a 1/48 scale remote (not radio) control Tamiya Jagdkanone Panzer I had in my teens, that driving each track separately can occasionally confuse.

Thanks, Lincoln T, for explaining the rating of brushless motors - it had been baffling me. They are rather expensive - �50 would be cheap for one, so it would almost need a mortgage to buy two with associated speed controllers� cry �Especially when one considers the cost of materials for the tank hull itself!

On that score, when I first started thinking through this last summer, I had thin plywood (about 3mm) in mind for a 1/16 tank; it would be cheaper and stiffer than styrene, but easy to work, unlike metal.

Worm gears I agree with - or planetary gearboxes. There are some excellent r/c tanks to be seen on YouTube, but the screech of spur gears quickly becomes tiresome.

TinCanTadpole · Legend

Paul Bonnett wrote:
Having recently seen a 1/35 FT17 r/c and with working turret and suspension I am thinking along the lines of 1/16 for a complete scratchbuild or maybe some very serious work on an Emhar 1/35. Will all depend on my level of sanity !
Paul

�I seem to have taken over this thread somewhat, with my requests and long posts.

Paul, if you're still following this, does converting an Emhar sound any easier now? I know there's the Male sponson to consider, but in r/c terms, maybe it just needs a pair of continuous rotation servos linked through a mixer to the receiver, some batteries (obviously), and perhaps a few sprockets and a couple of short lengths of small roller chain to take the drive from the servos to a pair of drive sprockets (or pulleys and a rubber band). That, and maybe some Model Cellar tracks, which I see cost more than the tank itself...

May not need to worry about sanity after all?

LincolnTanker · Commander in Chief

Hi TCT, the brushless motor/speed controller combos are now quite cheap, on the link I posted look at�

Combo - EMax CF2822 1200KV (145W) Brushless Outrunner Motor (409938) & BRC 20A ESC (400264). brcrb233

The motor/speedcontrollers are max 0.2hp each at �16 each. A 2 cell Lipo should give plenty of slow clmbing power.

TinCanTadpole · Legend

Blimey, that is cheap! Mind you, the devil may be in the small print; it says it's for aircraft use, which means it's only likely to work in one direction - no reverse!

The unfortunate thing with brushless motors is that they draw huge currents. The 10A continuous specified for the example you found is more reasonable than most (which draw about 30A, often more), but I've done some more digging myself and found a 370-equivalent (upgrade from) brushless that's rated 6A maximum - the sort of figure I'd be hoping for:

motor

�

Rather less powerful, and a very small size, but with a 4100Kv rating, it would need a gear ratio of about 300, even 400:1, which should give big torque.

BC312 · Colonel

I have started a new topic to follow upon RC 35th scale modeling or any other RC scale model sizes, if anyone would like to add. See under Modeling.

-- Edited by BC312 on Sunday 19th of February 2012 11:13:02 AM