TOPIC:

While researching the logo, I found these from 1976, 1978 and 1984 respectively:

The DPDT switches didn't arrive so the front cab still isn't finished, but I've hooked up the rear cab, including the motor drive - everything  must be wired up correctly as everything wheelspun (trackspun?) on the bench in the same direction  

I cut & added slightly tweaked logos to the rear mudflaps, it needed something as from the side & rear it's just black from the waist down. 

The bogus numberplates date it to 1983/84, possibly a bit early compared to the actual UK road registered 1:1 Hagglunds I found photos of, but plausible enough.

I still need to hook up the lighting wiring in the rear cab & do some cable management, but it's getting there

The ladder/stretcher in in the shed outgassing from a 2nd coat of nitrocellulose sanding sealer.

Rear cab wiring hooked up, seats & roof installed.

A lot of the 1:1 versions have a strain relief rope on the umbilical, I think it probably also stops the cabling swinging out beyond the sides of the cabs at extreme angles.
I don't need the first function & the geometry (and distance between the cabs) is wrong for the 2nd, but I replicated it with a bit of Glace cotton thread anyway

Still waiting on the DPDT switch (and you never know, every year before now there's been a a mail delivery on the Sunday before Christmas, and deliveries can be as late as 1830) to properly complete it, the ladder/stretcher is back in from the shed, the only other thing I really need to do is to keep a battery charged & wait for some snow.   

I may try for better indoor pics, but it's 1000mm long x 310mm high x 320mm wide and flops about in the middle: not so easy to get a posed shot as, say, a Karmann Ghia

It is fantastic Jonny.

Great outcome of this beast!
I'm looking forward to see snow pictures of this.

See what I found from my army duty time 98-99'
Sadly there is no more pictures of these.

The DPDT switch(es) arrived, so I soldered one on - not fun due to having to use the soldering iron inside the front cab, thanks to doing it very late in the process.

Everything works fine - and by "fine" I mean "works fine regardless of switch position"

Once I was positive the switch was wired "correctly", it meant the cause had to be something else I'd done, not the way the PO had wired the switch. It's having a UBEC power the RX without a switch in the feed, so as soon as the drive battery is plugged in, the RX gets power, and so do both ESCs: on the +4.8v/6v servo lead, as well as the battery in.  

I'm not sure if all ESC behave like that - i.e. work as "on" even if the switch is "off" if you apply current through the servo plug +ve - or it's just this model. I may experiment at some point in the future, but not right now.

I've got two options -

1- leave things as they are & zip tie the new switch - in either position - out of the way, and plumb the existing/old single pole switch in to the feed from the UBEC to the RX - in which case a single switch effectively controls everything, or- 

2-  remove the +ve pins from the servo plug on each ESC, this would mean the RX would be on from the moment the battery is plugged in, so if the TX is also on - but the ESCs are off - I have a "safe" demo mode for the lights & snowplough, without any risk of a large & ungainly model off the bench.


 I'm kind of leaning towards the 2nd option - it'll be great, right up until the point I'm out in the snow wondering why the badword the lights & plough work, but the drives don't  

Coming along nicely, Jonny. Seems the swedes are keeping you busy.

1:1 scale Bv206 on eBay - www.ebay.co.uk/...4669730548  

I think there have been 3 occasions in winter here in my lifetime that one of these would have been really useful, probably the same again where I could have used one, but it wouldn't have been essential - oh to have space & money for such toys. I wonder how much a Kettenkrad goes for ...

In the meantime, and still waiting for snow, a small bit of white cloth & 1970s wallpaper is not the best backdrop, I'm not sure these pics are much better than the previous ones. Still they don show it strapped down on its transport ladder with the genuine ARNO (OE for 1:1 Hagglunds) straps. Shame they only come in olive.

 

This is such a cool project.  I'm trying to make sure I understand how it works.  If I understand correctly, both the front and rear cabs are driven.  I don't think you have a PTO going from the front to the rear, instead you have a pair of motors in each cab.  Is there also an ESC and battery in each cab, or are you running both off a single ESC and battery in parallel?  If the latter, I assume you are just sending power to the rear motors through the umbilical.  It doesn't look like there is any kind of servo control of the tether for steering.  Are you skid steering both the front and the rear in opposite directions or skid steering the whole train as a unit?  Or maybe doing all the steering with the front unit?

blakbird wrote:

This is such a cool project.  I'm trying to make sure I understand how it works.  If I understand correctly, both the front and rear cabs are driven.  I don't think you have a PTO going from the front to the rear, instead you have a pair of motors in each cab.  Is there also an ESC and battery in each cab, or are you running both off a single ESC and battery in parallel?  If the latter, I assume you are just sending power to the rear motors through the umbilical.  It doesn't look like there is any kind of servo control of the tether for steering.  Are you skid steering both the front and the rear in opposite directions or skid steering the whole train as a unit?  Or maybe doing all the steering with the front unit?

 I did expend a bit of skull sweat on the steering issue initially, the best/most complex plan was to have all 4 tracks powered by 2 ESCs with a tank mixer to slow one side vs the other with steering input, and have the angle between the two pods changed by two 540 motors & service mounted gearboxes mounted on gimbals, driving threaded rods into a hollow threaded tubes via UJ, powered by a further 2 ESCs (one reverse wired).

Other options were could I do it with one angle ESC, or whether a single angle gearbox would do, and where those could be fixed.

There were problems with the above approach(es) – cost, complexity, weight, battery life, and not least of all, the fact that the chassis are lower at the front than the rear, and are pretty flimsy if you try to start applying torque in directions & places never designed for.

That would mean extensive bracketry meaning more work/complexity/weight etc etc. Before committing to that (but not before buying Como combined motor/gearbox units


I thought what if I do none of that, making the setup as mechanically and electrically as simple as possible – had to be worth a bit of time kludging & test driving anyway.

The final setup is very much as it was from that first test drive – one battery in the front compartment drives two ESCs in the front, the left TX stick controls the right ESC which drives both right side motors (the rear pod right motor is powered by two of the fake “hydraulic” hoses), which turn the left tracks on both pods.

The right stick controls the left ESC, which spins the left motors (the rear one is connected by the other two “hydraulic” hoses), which turns the right tracks. 


The floppy “umbilical” cable is two switched 6v lives for the two different LED lighting circuits in the rear pod, and two earths – one of which may be superfluous

The physical connections between the two pods allows for turning (and some horizontal angle between the two pods) at the middle, extra horizontal and some degree of twist comes from the fasteners (nylocs, or double nuts) at either end being left with gaps.

I think this is an acceptable level of kludging in a 1 off prototype, but if this was ever going to be a production item, mk.2 would probably be longer studding (allthread sections) and springing, mk.3 (cost reduction) would be a 1-piece bar with round ends & suitable cups on the chassis, or more likely the other way round (think pointy end of Wild Willy M38 or Clod suspension arms, just for linear movement instead on angled).   


In practice, it drives like a regular 2 stick tank – although you can’t turn on the spot. I found using 60% throttle on both TX sticks makes adequate progress, and to turn you can either increase the speed on the tracks that will be on the outside of the turn you make – i.e. increase left throttle to turn right – or reduce the speed on the tracks on the inside of the turn, i.e. reduce right stick to turn right. Or you can do both.

It’s possible to turn too tight, in which case the tracks of one pod will try to climb those of the other. A “mk.2” fix would be something like strapping to tension limit the movement of the pods, mk.3 might be a single telescopic device, closed length would limit it one way, full length the other. 

Reverse turns are possible, even when the pods are already cranked, but it’s best to keep the speed down to 40% of maximum at the very most to account for the extra thinking time. 


Mk.2 fix for the throttle issues would be to use the End Point Adjustment on the TX to 75 % forward, 40% back, the mk.3 would be that, plus secondary TX gimbal springing to set “soft” limits of 60% & 25%, but you could push through those for turning speed(s). 

I don’t tend to go back & make fixes like those, but I do think about what it would take to “productionise” these silly one offs. In addition to the above, if Kyosho were to make something like this, in addition to the above you’d have to make it as light as possible, that would mean polycarbonate bodies with blacked out windows on the front, no interior, and omitting the rear body entirely in favour of  a flat load bed & minimal headache board, and restoring the weight balance between the two pods by having a single race pack in the back.   

The current Kyosho snow / tracked offering is the Trail King at around 325 GBP, a Hagglunds front body is 4x the size so there’s a material cost there, plus likely a much higher vacform pull failure rate & the need for a bigger machine &  a larger buck, there’s savings in only one TX & battery needed, but extra in joining the pods, you’d either need 4 of the weeny ESCs or two better ones, one bigger box is not necessarily the same cost as two smaller ones, there’s licensing etc… I think Tamiya full option tanks & trucks prove there is a market for big, expensive RC, but a snow whatsit is already pretty niche, how many would want to pay twice (or more) as much for something with twice the storage problem, and is arguable less capable than a standard version? 


TL;DR – simplest solution works fine with operator sympathy