Radio controlled road vehicles on Upper Benllech

[BG John]

I don't know if you've seen them, but the Chinese "Coke Can" RC cars don't use a servo for steering. They have an electromagnet that attracts one of two magnets on the steering arm depending on which way the current flows (I think). I dismantled one last night to see if they are any use for cheap RC projects, if you want photos.

[Robin2]

Speechless (after seeing Reply #50)

 

And can't wait to see more

 

...R

Edited January 20, 2017 by Robin2

[Giles]

Excellent! I have hacked a couple of large servos in the past for the fun of it- to use as a reversible ESC - but at this size......

 

Brilliant.

[Corbs]

I don't know if you've seen them, but the Chinese "Coke Can" RC cars don't use a servo for steering. They have an electromagnet that attracts one of two magnets on the steering arm depending on which way the current flows (I think). I dismantled one last night to see if they are any use for cheap RC projects, if you want photos.

I wonder if they could be put to use to remotely operate couplers on locomotives, negating the need for uncouplers in the track?

In a similar way to this 

http://precimodels.com/en/

[BG John]

I wonder if they could be put to use to remotely operate couplers on locomotives, negating the need for uncouplers in the track?

In a similar way to this 

http://precimodels.com/en/

Something that works with a bit of string! I like that. I wonder if it would be worth the effort. I think there would be an easier or better way to do that, if all you wanted was to operate the coupling, than to buy one of these cars.

[davetheroad]

I wonder if they could be put to use to remotely operate couplers on locomotives, negating the need for uncouplers in the track?

In a similar way to this 

http://precimodels.com/en/

 

I think the radio controlled aircraft hobby has things called actuators which look like little electromagnets, Some of them are really tiny and I wonder if they could be used for uncoupling by attracting a suitably modified tension lock hook so it raises Maybe better than the servo driven ones. I know Deltang receivers have connection pads which could possibly activate an actuator?

[Robin2]

I wonder if they could be put to use to remotely operate couplers on locomotives, negating the need for uncouplers in the track?

I suspect it is not sufficient to have uncoupling only on locos. There will be times when you want to uncouple wagons.

 

I made an InfraRed controlled uncoupler for an N-Gauge wagon with a DG coupling. But then I realized that it would be enormously difficult to identify the wagon on which you want the uncoupler to operate. Track based uncouplers are easy to identify.

 

So if you need track based uncouplers for the wagons you might as well also use them for the locos.

 

...R

Edited January 21, 2017 by Robin2

[Corbs]

True, but a mix of both kinds would allow more flexibility in operation.

[PhilJ W]

Back to the teaser photo.

Giles was right, it is a 3d printed chassis block.

 

To assist in building the layout, I want a 'smallest' vehicle, to set the worst case road conditions.

Much like using the shortest wheelbase 4 wheel loco and largest beheomoth loco that you want to run, to test the track quality and clearances.

 

So this is my ambition.

_20170117_215913.JPG

A Model T Ford, WW1 ambulance kit from RPM models.

Officially, its 1:72 scale, but the wheel base is 33.5mm which scales out to the 100" standard of the Model T at 1:76, the track is a bit closer to the 1:72

Anyway, its close enough.

Whilst the body is relatively large for a car based van, its still very small.

In fact its smaller than any of the servos I have used in the past. So I am going to try hacking one smaller.

Internally; it contains a bunch of gears, the motor, feedback pot and a very small PCB.

Putting the gears to one side, that leaves these parts:

_20170120_211142.JPG

So I have designed an insert to fit inside the back of the ambulance, Starting from under the drivers seat and extending back until just past the rear axle.

This takes, a pair of 4mm motors for drive and steering, gears, and the servo pot. along with all the bearing mounts including the rear axle bearings.

The new servo will have less torque than the original, but from experience, they provide much more than these little kits require.

Whether this will all work is all an interesting risk, so I may have to completely redesign it and certainly expect to take several attempts to get things working.

 

I printed it at work; where we have a Form 2 SLA printer and a CEO who is positively disappointed when engineers don't use the printers for home projects.

This all fits approximately here.

_20170117_215956.JPG

I haven't started hacking the kit yet. Just removed sufficient parts from the sprue to measure everything.

I am also still waiting for the gears after I discovered that I had not completed the order properly.

So I have had to delve into the spares box to get this far.

 

To ensure the shafts run smoothly, I have inserted thin wall brass shells into the bearing holes. The tubing comes in telescopic sizes that are in 0.2mm increments.

I.e. the 1.0mm fits inside the 1.2mm which fits inside the 1.4mm etc.

Hopefully these will stay put in use.

 

The RX, servo PCB, battery and charging socket will be scattered around the kit once I have more confidence in where the spaces are going to be

 

I haven't decided whether to stick with the kit as supplied, and paint as a civilianised, ex war surplus truck

or give it a new body and back date it to pre-war.

I'll worry about that as and when I get it all working

I have a couple of these kits. The rear body appears to be a bit on the narrow side so it might be an idea to scratchbuild a wider body out of plasticard.

[otherplanet]

I don't know if you've seen them, but the Chinese "Coke Can" RC cars don't use a servo for steering. They have an electromagnet that attracts one of two magnets on the steering arm depending on which way the current flows (I think). I dismantled one last night to see if they are any use for cheap RC projects, if you want photos.

Thank you. I modified a couple of these a few years ago. I built a new body for one, based on a (heavily stylised) Hillman Imp.

Full sized Hillman Imps are one of my other interests and I have happy memories of driving this little car around the beer glasses at one of the club weekends.

It has no internal modifications, just the new body.

 

 

I would be interested whether they have evolved and if so how. The limitation was that the controls were very digital. i.e. full left, straight on or full right. please share some images.

 

 

I think the radio controlled aircraft hobby has things called actuators which look like little electromagnets, Some of them are really tiny and I wonder if they could be used for uncoupling by attracting a suitably modified tension lock hook so it raises Maybe better than the servo driven ones. I know Deltang receivers have connection pads which could possibly activate an actuator?

 

They do indeed. I used one for the steering in the Scarab and they do provide a more analogue control. The RX4#'s have a pair of F bridge outputs for driving them. I considered repeating the method in this T, but the subsequent experience with the servo equipped vehicles was so much more precise and less inclined to tramline down every blemish in a model road surface, meant I was keen to try the servo route again. however, I hold it in reserve if things don't go as planned.

 

I do like the idea of using the coke can steering as a donor for uncoupling actuator. The Atkinson uses a memory wire to operate the tail hook. but its not very satisfactory.

 

The RX6#s receivers have programming to use a servo for functions such as uncoupling, even to the extend of using only half the stick movement to actuate them (so you can use the other half of the movement to actuate one at the other end).

Ironically, although more complicated and sophisticated, the small servos are cheaper than the actuators. I suspect they use less current to hold the steering at an angle too.

[NRS91]

Loving the Imp!
We have a few of them lol

[otherplanet]

Goodies have arrived. An array of gears and worms.

 

I bought 2 sets, with the ambition of using the same basic design for something else.

They have updated their packaging since I last placed an order, with these delightful laser cut holders for all the gears.

[Giles]

....looking forward to this!

[SimonME46]

Utterly brilliant. Really enjoyed the video, thanks for putting that together. Great to see how you run wiring etc, please keep us posted!

[otherplanet]

I have cleaned up the mounting for the bearing cap, and then drilled out the holes for the bearings

 

The bearings are cut from 1.2mm OD brass tube.

I run a 1mm drill down the inside to clean out the bore, and use a 2.5mm drill on the end to give a smooth and slightly chamfered end.

Then slide a 1mm piece of steel wire down the inside, before cutting with a scalpel. rolling the tube back and forth under the blade.

 

Once removed, the bearing needs the second cut end to also be chamfered with the drill.

 

I now have all the bearings, including a 1.4mm OD bearing for the Potentiometer shaft (servo Horn).

The final drive shaft for the wheels is also shown.

They are tacked lightly to a piece of double sided tape to prevent them escaping to the floor, never to be seen again

            (or at least until after I have made replacements).

[otherplanet]

I thought it be worth sharing an image of the CAD model. This is what I am aiming for.

The servo gear train is all at the left of the view, the drive on the right. in theory the model is built such that the length is adjusted by only one parameter and the axle height by another. (within limits).

 

 

The motors are buried in the block, you can just see their ghost through the transparency.

The plan is to attach the steering arm directly to the large gear, rather than have a seperate servo horn.

The Axle passes through the large bulge, centre right.

The rectangle on the rear corner is the power switch.

The near left face will glue to the front half of the kit. hopefully to the inside / underside of the drivers seat. If I have got the length calculations on the kit correct!

[19Ted54]

Geoff,

 

congratulations, I think you've got a winner here! Would it be too much asking for a *.pdf about this steering\drive\gear box arrangement once it is finished - with all the motor specs, the specs for the gears and everything else. Will you be offering the 3D print to us mere mortals here?   

 

Greets from Austria, Edward

Edited February 11, 2017 by 19Ted54

[Giles]

This is genius....

 

An integrated steering/drive module.

[otherplanet]

Hello.

Sorry for being off grid for a while. Family, work and life in general have prevented any progress for a while. However I was recently able to make some progress.

The basic chassis took a lot of fettling to get it working. In particular the alignment of the rear drive shaft was difficult to achieve and many of the clearances to the gears were too tight, requiring more cleaning up than I would have preferred.

I will need to amend the design before using it again.

 

There is still further work before it is ready to use and then of course it needs to be built into the model.

The video shows the two drive trains running on the bench for the first time.

 

https://youtu.be/zffQlxQJw40.

 

 

[Giles]

It may need a little refinement (from the manufacturing aspect) but it really is brilliant! Wonderfully thought out.....

[19Ted54]

Geoff,

 

great to see that you are back to the workshop and making progress!

 

Just a thought - might it be possible, whilst you are amending the design, to split the two components and offer the servo as an 'extra'?!

What a design!!

 

Greets from Austria

[otherplanet]

Geoff,

 

great to see that you are back to the workshop and making progress!

 

Just a thought - might it be possible, whilst you are amending the design, to split the two components and offer the servo as an 'extra'?!

What a design!!

 

Greets from Austria

 

I think that it should be fairly easy to do a servo only version, once the basics are working.

The changes I am planning to how the potentiometer shaft is mounted should help towards such a change as well.

The other major change is to split the back off the final drive of the traction motor, so that the shaft can be slid in from the rear. Allowing the front bearing to be more conventional than the current split housing. The bearing tube is such thin wall, that clamping the two halves together was enough to prevent rotation of the shaft.

[otherplanet]

With the main drive system now working, my attention is now focused on the front end. The detail of the RPM kit is pretty good, but doesnt lend itself to making working steering or compensation.

 

So I turned to the 3D printer again, and with a combination of reverse engineering a scale line drawing of an brass era model T, and the dimensions of the kit. (which dont quite match incidently).

I managed to make these.

This is 2 sets of axle, grill and bonnet. (2 sets for when I break one).

To achieve some compensation, the spring is joggled backwards as it fits behind the yoke. with the engine block on the other side, this creates a box joint. A hoop extends up from the top of the spring around the starter handle, which provides the pivot, so the whole axle rotates about the starting handle.

 

I have allowed for some wire radius arms to run back to the crankcase (not fitted yet), to help stiffen things and hopefully make the axle survive running abuse.

the grill and crank case glue to the underside of the chassis, the bonnet to the top.

Apologies to any Model T experts, I am aware that I have created a bit of a frankenstien hybrid of model years. the brass era grill and non louvered bonnet do not go with the pressed steel firewall and fully curved wheel arches. with hindsight, I should have gone for the other version of this kit. but hopefully no one will mind or notice too much.

 

Anyway. I still have to actually get it to work.

 

oh PS, for those who asked. the dimensions of the motor servo case are:

Length 19.5mm, width 14mm & height 7mm top to bottom of chassis rails, 9mm top to axle centre and 11mm top to lower edge of differential case.

[otherplanet]

Youtube suggested this video to me today.

I wish it had been available when I was building my first vehicle

Just over 20 minutes of original Scammel advertising film, complete with full details of how the coupling works.

detailed working views of various trailers, and fantasic footage of them showing off the tight turning circles etc.

 

https://youtu.be/4yR-5bbFivU

 

Makes me want to go back and build some more.

Edited May 24, 2017 by otherplanet

[Robin2]

20 minutes of original Scammel advertising film,

Very entertaining.

 

I don't think I ever saw a real one (in Dublin) but I had a Dinky model and I am amazed to see how closely they reproduced the coupling system.

 

...R