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Radio controlled road vehicles on Upper Benllech


otherplanet
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Hello, I've been working on OO radio controlled road vehicles since Autumn 2012 and been aware of the work of Giles and Grasslands since last year via Youtube. However, I am only a recent forum member since Phatbob nagged me about putting some information up about the Scammell Scarab and Atkinson steam wagon I was running on Upper Benllech last weekend at the Chapel-en-le-Frith show (New Mills and District Railway Modellers)


see link http://youtu.be/w_X2WZ4RliM


 


They are both heavily kit bashed: The scarab was built for Upper Benllech and started as merit kit, donating the trailer, chassis and most of the wheels, it took about 4 attempts to get the coupling between trailer and tractor correct so that the power was reliable but the connection not too stiff. An Oxford diecast model provided the heavy cab and grippy front tyre, to solve the problem of it going straight on when the steering turned. (I understand the original had a similar problem).


 


post-25615-0-48892900-1425233898.png


The Atkinson started off as the Kiel Kraft kit (now Knightwing) this provided the wheels, cab, boiler and the steam motor. But I built a new brass chassis plus a new tipper body. I remodelled it from the 1924 version of the kit, to a 1916 version, with larger tipper overhang, no mud guards and the screw jack tipping mechanism, as my other longer term aim is to build a fleet of Edwardian / early inter-war period vehicles. It is considerably out of period for the layout, but until I have more in the 60's fleet, it will have to do.


post-25615-0-59189600-1425233942.jpg


 


The Atkinson behaved well, especially once I corrected the inverted steering (that messes with your head.) but the scarab proved too fast to control nicely and the receiver keeps losing signal with the low sensitivity (throw) transmitter I built for it. Never the less, they both received a lot of attention and provided nearly as much entertainment to the viewing public as my disgraceful driving.


 


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Quite superb - as you say, the Scarab is rather fast off the mark - ideally a higher ratio gearbox would be the thing - but there's really not very much choice. The video doesn't really show quite how small the Scarab really is, and therefore what an achievement it is to pack everything in there (at least the motor/gearbox and servo have got to be in there.....!)

 

The steam lorry is also delightful. In neither case is there a 'give-away' as to obvious technology on view -not easy with the size.....

 

Please post some photos and info as to what and how you've done it - I for one would be fascinated to see.

 

(You'll get very bored with people talking about how it's done by 'Faller')

 

Giles

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Thank you all for your positive comments / feedback.

 

You are right Giles about the Faller references. We got quite a few at the show. plus a lot of people who assumed that it was Faller, , ,  until I did a 3 point turn. at which point you get the raised eyebrows and the puzzled look. And then the questions.

 

To explain the workings I shall have to break it into installments.

 

I'll start with the Scarab, as thats where it all began. Operating Upper Benllech at the Croydon MRS exhibition in 2012 we discussed how the big yard and long road down the back was a fantastic opportunity to run road vehicles, but Faller wouldn't do the job, even if we could slow them down, the manouvers needed for the yard required better control than a buried wire would offer.

 

Scammell Scarab.

As mentioned previously, the scarab started life as the Merit kit. It uses the tractor chassis, seriously hacked about to clear the gubbins, plus structure to support the steering and stiffen things up. The front steering yoke is cut from brass box section, and uses a romford crank pin for the vertical axis.

The actuation uses a proportional actuator from indoor micro aircraft. I found Micron Radio Control particularly useful.

The actuators are used to operate the rudders on aircraft (they do OO scale radio controlled airplanes!) and use a pair of magnets pivoting inside an electromagnetic coil. It doesn't have a lot of power, and I ended up adding some extrs soft iron to centre the steering as even the lightest spring was too much.

The actuator drives the steering via a link arm from brass wire (thats about 1mm dia for scale reference).

I can't remember why I mounted the coil on the vertical axis, I had a good reason that had something to do with space, it does mean the connections have to cope with both axis of movement, so they use a simple ball and cup made by filing a collar on the link to match a countersink. A minature eclip holds it together.

post-25615-0-12960400-1425337811_thumb.jpg

The yellow circle above the front wheel is the surface mount LED, it lines up with a short length of fibre optic in the nose to create the lens.

The PCB on the far side is a RX43d-v5 from the deltang range. It is a little large and I originally used the Rx45-v5 but had a slight polarity incident with the trailer connection and it went phut. I had the Rx43 ready for the next project so in it went. One day I might correct it, but the wires are glued into their routing so it will need some impetus for me to change things. The strange black blob is the head and shoulders of the driver. there was so little of him left, that I decided to stick with a sillouette in the window rather than attract attention by giving him colour.

post-25615-0-79287300-1425337881.jpg

The motor gearbox is mounted between the frames, its has an epicyclic gearbox in the black section. it came from Precision Microdrives who do a wonderful range, they look very similar to those on the mikromodellbau etc websites, I dont know whether one gets from the other or they have a common source. But Precision Microdrives also provide a full data sheet as they are really targeted at commercial clients. I have also bought gearmotors from Gizmozone who also provided the bevel gears (and the previously mentioned eclip). The rear axle runs in metal bearings inserted into the mouldings to reduce friction and hopefully, wear.

You can see the extra space infront of the motor, where there used to be a lower ratio gearmotor. It felt painfully slow when I first built it. However, after the Chapel show, I will be changing back. Incidently, this is the third motor. Number 2 was so fast I could race my son's RC integra down the hall, until straight line stability got the better of me!

 

The result is a very small model.

post-25615-0-59867300-1425337976.jpg

With the entire drive train, steering and control fitted into the tractor. Which leaves only the battery to fit on the trailer.

That does present its own challenges. I'll cover the 5th wheel coupling in a day or two if your interested.

 

 

Hope that all makes sense, but please ask if you have questions.

 

 

 

 

 

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Sorry for the delay in finishing off.

 

Scammell Trailer

 

With all the motors, steering, receiver in the tractor, the trailer only has to hold the battery.

Unfortunately this involved getting the power out through the coupling.

This proved tricky to get right, as the balance of reliable connection and lightness of operation eluded me for a total of 4 rebuilds.

The version in the original youtube video only had 2 degrees of freedom (it didn't tilt) and whilst this was reliable(ish) the trailer would cock its leg on corners and was intolerant of uneven roads.

 

The final version uses an approximation of the original scammell coupling

post-25615-0-35754700-1425940460_thumb.jpg

The main fork pivots in the trailer on a Romford crank pin as the bearing, this is soldered to a piece of brass U section that carries the yoke.

Power is carried via a brush on the shaft, and a copper pin pushed against a flat washer on the underside by a small torsion spring I wound myself.

The yoke has two rollers on the outboard ends that use romford crank pin bearings, and these snap into the matching clips on the tractor that are made from brass sheet and phosphur bronze wire.

This picture before it was painted shows things a little clearer

post-25615-0-04566700-1425941261.jpg

The trailer carries the 90mAh battery, a charging socket and the on-off switch, under a deliberately low profile load.

post-25615-0-02736300-1425941283.jpg

 

Despite all this, the central bearing was still a little stiff, and the front wheel still very slippy. So I added the Oxford diecast cab, and weight in the packing cases. Over all it now weighs a heady 26grams.

 

 

However, once I had got it all running, I decided that it was possible to take things just a little further

so I also packaged up a tiny 20mAh battery into a tarpaulin, whilst it looks a little chunky, in never the less, offers an extra party trick.

post-25615-0-89328600-1425941681.jpg

I dont use it very oftem, as the capacity is so small, it can only run a few minutes before running out of power.

 

I have to mention the Mechanical Horse Club, when I was trying to get the details right on things like the wheel sizes etc. I contacted them for information. They were very helpful and sent me detailed line drawing files of the 3 and 6 tonne Scarabs, enabling me to finish off several of the details

 

 

 

 

 

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Remarkable - quite remarkable.

 

The mechanical horse is a delightful (and most appropriate prototype anyway) but has to be one of the most difficult - for all the reasons you've shown. Your solutions are brilliant and beautifully engineered.

 

I should love to see this in the flesh sometime. Congratulations!

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Brilliant, but for my preferred period I need four legged horses, not mechanical ones :jester:

I keep thinking about it. I've experimented with building O scale moving automator.

post-25615-0-47246800-1426024425_thumb.jpg

The concept was for it to reach out and 'drag' a skip wagon sideways and then push to tip the contents down a spoil heap

However, it didn't work very well, so it got bookshelved.

 

The actuating cam mechanism was intended to fit under the baseboard, definitely not inside the body

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Peoples ingenuity never ceases to amaze me, Ive seen RC in 'N' gauge recently and I expect that soon we will have little drivers steering and changing gear in 7mm/4mm vehicles!

 

Thanks for the continued inspiration!

Thank you for the feed back. I have seen a youtube video from Germany of a HO truck where the steering wheel was connected to the steering servo and then the driver had articulated arms so that he 'steered' the vehicle. I believe it was driving over one of the 4x4 all terrain tracks they use.

No gear changing though!

 

I have wondered about making the driver's and fireman's arms extend to signal on a future wagon, getting the circular motion might be a bit complex. it seems such a waste of the deltang indicator function on a vehicle that predates electric lights, trafficators etc.

Not today's project though.

 

I have since the last show, finally got around to programming the head and tail lamps into the receiver on the Atkinson.

Whilst getting the driver to walk around adjusting the acetylene is a bit much, they do 'light' one at a time.

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Remarkable - quite remarkable.

 

The mechanical horse is a delightful (and most appropriate prototype anyway) but has to be one of the most difficult - for all the reasons you've shown. Your solutions are brilliant and beautifully engineered.

 

I should love to see this in the flesh sometime. Congratulations!

Thank you, as a master of the art, your feedback is most appreciated.

 

As Phatbob says, we are due at Liverpool on the 25th and 26th April if you are around to see it 'in the flesh'. I don't know when Upper Benllech is booked out after that.

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  • 2 weeks later...

Ok the post show fettling is done:

Scarab remotored to improved control

Scarab trailer coupling modified to prevent one of the brushes coming unclipped when fitting the trailer

Home made controller 2, unused channels tied to "centre" instead of floating hopefully this will prevent the random loss of connection with the scarab.

Home made controller 1, updated to add channels 1&4 in lieu of my off the shelf parkzone transmitter that died during the show

         Not yet reassembled as I want to try adding a 5th channel to give the Selecta function a try. but its low priority.

having channels 1&4 enables

Reprogrammed Atkinson reciever to enable (some) party tricks

    Headlamps and tail lamp now work

    Tail hook now operates, but doesnt actuate as far as desired (not reliable uncoupling, but good enough to enable a trailer to be used)

    Tailgate release now powers, but unfortunately doesnt activate due to excess resistance - problem for the future.

 

So I can now aim for the next show:

so onto the modelling bench arrives -

post-25615-0-77323300-1427019620.jpg

The original bed from the Atkinson. Whilst it didn't fit the era that I wanted, its good enough to repurpose, so the plan is to add some wheels from a prieser farm wagon on a simple chassis with a drawbar to the front axle.

 

and -

post-25615-0-52203500-1427019631_thumb.jpg

This little Austin 3way van. The plan had been to convert a Bristol L6 bus next, but Chapel indicated that the goods vehicles had more potential as they can be driven over further areas of the layout and have reasons to stop. It also highlighted the need to restrict the size as although Upper Benllech is unusually rich in tarmac acreage, it is still remarkably restrictive once you start driving on it (especially if your driving is as bad as mine).

So this little Austin had already been bought with future plans in mind and it has raised up the priority list.

It has been deliberately picked to be just large enough to not cause extra problems, so I am hopiing it will be an easy / quick conversion. Even so, having it running by Liverpool exhibition is looking a little tight on time. We shall see.

 

 

 

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  • 4 weeks later...

Well the K8 is not looking like it will be ready for Liverpool.

The steering knuckles have been fighting back, the kingpins have insufficient metal around them to hold in place, which is a shame. As the axles were pressed into the hub I was trying to incorporate the bearings into the knuckle but it just doesn't fit. so I will have to resort to plan B and try to build bearings to press into the wheel hubs. Unfortunately this is not likely to get done in time as the remaining weekend is full.

 

The picture shows attempt 3 or 4. just prior to cutting it off the end of the stock tube.

post-25615-0-68987800-1429048740.jpg

 

 

On the other hand the trailer is going well.

 

post-25615-0-54378300-1429048727.jpg

Just needs painting now. (which is already under way)

 

 

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The trailer is done, not quite achieved what I was hoping for but it will have to do as there is no more time before the show. post-25615-0-92680800-1429559156_thumb.jpg

Its deliberately a lot tattier than the Atkinson, as is intended to be an old, half redundant piece of kit. I was a bit worried about how the wheels would cope with running on the rough road surface if they were painted, I had visions of them returning to their native styrene. But I managed to make a set of rims by flattening some soft iron wire in a vice until it was only a few 100 microns, and then formed new tyres to fit over the plastic moulding, hopefully now they will either wear shiny, or naturally rust.

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  • 3 weeks later...

We had an excellent show, with lots of interest in the layout and the vehicles. Lots of good questions, the upgrades proved worthwhile as the Atkinson managed a good hour running between charges and the Scammel at least 2.

The Scammel gearbox change also proved its worth, the improved control meant that reversing was much easier. With an exhibitions worth of practice, it became possible to do a reverse park quite smoothly, there is a definite technique to getting it to go where you want.

Try doing this with Faller car system:-

https://youtu.be/hOa-fAy97NE

Note, this is recorded on the first day, I had it much smoother by the end.

 

The Atkinson trailer ran very well, but proved unusable as the result is a vehicle that is too long to negotiate the tighter turns and goods yard gate. Its a little dissappointing, but a useful learning excercise for future layout and vehicle design.

 

We also took a brief visit to Scotland

post-25615-0-98456500-1431033579.jpg

 

With a brief run on Kinmundy, the roads are a bit short for a decent run, but the scenery is gorgeous and it photgraphs beautifully.

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  • 1 month later...

Hello,

Sorry I've been off grid for a bit. Family, household and work priorities have a tendency to slow things down quite a lot.

However things haven't been entirely without progress.

Following the problems with the first steering knuckles, the new version is now completed and I am fairly happy with it.

At least until I can get the rest working and see whether the wheels fall off.

 

post-25615-0-64468600-1435784729.jpg

The new version uses 0.8mm brass wire as the axles, glued into a 1.5mmx1.5mm block with the steering arm soldered to it,

 

post-25615-0-11465100-1435784719.jpg

which is then cross drilled and has a 0.45mm Dia steel kingpin pressed through.

 

The main bearing is a piece of brass tube of 1.65mm OD,

The wheel is from the original Oxford diecast model, but drilled out to create a tight fit on the bearing.

The tyre is not as perfectly fitted as I would like, but with a bit of fettling, can be centralised and made to run true.

It is a fairly soft rubber, so grip shouldn't be a problem

 

post-25615-0-06657000-1435784757.jpg

The right hand version used a very short length of 1.2mm OD tube pre fitted as the end cap, but on the second knuckle, this proved to be insufficiently retained

so I tried some E-clips that I had forgotten about.

This proved to work very well. so will be reused in future,

Unfortunately, the only place I have found to buy them is in the US, where they postage costs more than the parts.

 

If anyone knows a source of 0.5-0.6mm ID E-Clips, it would be most appreciated. The best I can find so far is 1mm ID

 

post-25615-0-32332700-1435784772.jpg

The completed Axle with the central pivot for the compensation, this is cut from the next size up standard square tube,

The trackrod will require an additional pin for the link to the servo.

 

Thats all for now,

The next stage is to build the rear axle, I'm aiming to use a worm drive on the end of a gear motor to get the necessary ratios.

 

Maybe I'll have some progress in a month or two

 

 

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I'm amazed you can get E clips that small - I've never seen them..... Extraordinary.

 

As you know, I got round that problem the other way, by glueing flanged bearings onto the stub axle, which then gave me a nice seat for the wheel on the bearing and its flange. But yours is extremely neat......!

 

Very much looking forward to the next instalment!

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I'm amazed you can get E clips that small - I've never seen them..... Extraordinary.

 

As you know, I got round that problem the other way, by glueing flanged bearings onto the stub axle, which then gave me a nice seat for the wheel on the bearing and its flange. But yours is extremely neat......!

 

Very much looking forward to the next instalment!

+1 :)

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  • 1 month later...

Although availability of time remains low. I've had a few evenings to myself, so a little progress and another Inch pebble achieved.

 

Rear Axle.

With the smaller diameter of the wheels on the K8 (only 9.8mm diameter). The final drive couldn't be too big, or specifically hang too low.

Its built from steadily increasing diameters of telescopic brass tube.

The axle is fabricated from two lengths of brass tube that slide onto either end of a length of 0.75mm wire, to which the drive pinion has already been soldered to.

The pinon is tiny - Mod 0.2

post-25615-0-99815000-1440628415.jpg

The cross holes in the tubes are for getting solder into the joints.

 

The bearings are cut from the next size up tube. (2.4mm OD) The two on either side of the pinion are chamfered on their inner edges to add clearance to the worm,

a third ensures the long axle doesn't flop around.

I've decided to offset the motor to one side, with the servo to the other, hence the asymetry of the axle design. I would probably add a fourth bearing if both halves of the axle were the same length.

post-25615-0-43697800-1440628389_thumb.jpg

In theory this is over constrained, but in reality, there is enough clearance to the outer tube that makes the next layer, although the axle did need some 'cold forming' to get it straight and running true.

The outer tube supports the axle and features an aperture for the worm to fit into.

Onto this is soldered a short length of square section tube which has been cross drilled for the worm's shaft. Thia happens to be just the right internal x section to hold the worm axially. The interface is cut curved to match the tube diameter and very gentle filing of this profile is what defines the gear meshing.

The worm axle is cut from 1mm diameter steel and is a tightish fit down the bore of the worm.

post-25615-0-85210200-1440628430.jpg

Once assembled the wheels currently hold the axle in place, but I need to get some 1.6ID washers to put between the plastic wheel hub and the outer axle tube, this will reduce wear and friction/gouging.

post-25615-0-89825400-1440628401.jpg

 

There will be a coupling to tie this steel shaft to the motor, which will be a higher speed variant of the one used in the Atkinson.

But this will wait until I have the chassis built to link the two axles and to hang the motor from and know the exact length needed.

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