Kodiak AEV 3 Armoured Excavation Vehicle

[wibblywobbly]

I did explore that route, there is a device called a pico switch that does it. If I was running a standard 2.4ghz tx/rx and an aftermarket board, plus numerous speed controllers, I could do it. However, I am trying to keep the costs to a minimum and going down the RX18 route.

Now, the issue is that an RX18 controls motors directly, which is great, but:

Right stick will power two motors at the same time, though they can be made to run in opposite directions using stick left/right.
Left stick will power one motor in forward and reverse on left/right, but only one motor in one direction on stick up.

The Kodiak has;
Bucket motor.
Bucket arm motor.
Mid section motor.
Lift motor.
Turntable motor.
Dozer blade motor.
Two tank drive motors.

The other fly in the ointment is that an RX18 system does not use standard signals, so I can't use any standard RC kit like servo's or pico switches.

There are 8 motors to control, and preferably independently.

The solution that I am churning over in my head is to modify an HL tx.
Make a seperate box into which I can plug 3 crystals.
Install 3 seperate RX18's and receiver boards.
Install a 3 way switch on the tx that will allow me to flick between crystals.
Theoretically this will allow me to activate any one of the RX18's.

If that theory works then:
RX18(1)
Tank drive on right stick.
Dozer blade on left stick (use an elevation motor to cycle the blade up and down).
Turntable motor on left stick using turret rotation circuit.

...so I can run the AEV, and use the dozer blade at the same time.

RX18(2)
Bucket on left stick using turret rotation motor.
(Elevation cannot be used as this is a one way motor circuit)
Elevate/lower the excavator arm using the right stick. I could link the next motor to this as well so that the raise lower activates two motors, running them on left right will allow me to adjust the arm height.

...AEV will be stationary when excavator is in operation, so drive motors not needed.

This leaves me with one motor that controls that last arm, the one that holds the bucket. Now I can either link that to the same elevation circuit, so that the bucket rotates in when the arm lowers and vice versa, or, I can use a third RX18 and split out the shared motors.

I can install 3 led's on the Kodiak, one for each RX18 lighting circuit. This way I will always know which one is active.

If this sounds as confusing reading it as it sounds in my head, then we are on the same wavelength. lolol. As long as the HL tx will allow me to use multiple crystals and switch between them manually, then there is no reason why RX18's can't be daisy chained like this. If it is possible, then it opens up a whole new world of controlling RC models without needing speed controllers etc??

Once I have my replacement 3D printer part here, I will set about designing a small box that will take 3 crystals and a 3 way switch, and plumbing it all in. If it goes bang and produces a lot of magic smoke, then I haven't lost a fortune.

[AlwynTurner]

Hi Rob, I think I follow that (which worries me as my knowledge of electronics is limited ) but it sounds like a fantastic way of getting round the limitations of the RX18 board! What will having three sets of RX18 and receiver in the Kodiak do to power drain? I'm following this with great interest and you're doing a fantastic job on this - genius level innovation! Best regards Alwyn

[wibblywobbly]

Power drain should be minimal. The motors I am using are tiny, so don't pull much current. They are geared so generate enough torque to move the arms on the excavator, though as you can see in the vidoes it does mean that they move slowly. My guess is that if I was operating the excavator arms I am pulling less current than if the boards were in a tank that was being driven around.

I have found a supplier for a 3 way on/on/on switch on Ebay, so will order that and might actually make some progress on this little project.

My view is that that the RX18 is a great board, the tx batteries last forever, and a tank will run around all day on a single charge with a decent battery. If only HL could stick decent sounds on them??

[AlwynTurner]

Hi Rob, I totally agree about the sound with an rx18 board. I am very much into budget tank modelling and would love to get some decent sound on my converted abrams. I'm sure some electronics whizz on the forum can come up with something cheap and cheerful (please?) Alwyn

I have since found a german module that can be used with an rx18 but costs more than an IBU2 card - where's the point in that!?

[wibblywobbly]

Is that the Bieier card? I just wish it was cheaper as well, it's a great card for sounds as long as IR isn't needed. Maybe we should pester the IBU people into doing something, if it was £50, had sound, no IR and powered multiple motors it could be used for all sorts of projects. It would also have applications outside of the tanking world.

Looking at various forums over the years, there are people using the RX18 in all sorts of models. Boats are one area, it can be be used on twin prop boats as it runs two motors, and allows fwd/rev as well as the motors running in opposite directions for low speed turns?

I have now designed a box to hold three HL crystals, and a 3 way switch, so once I have all the bits I need I will be good to go with the experiment. I might be raiding Dave's store in Manchester. I have two RX18's, so need a third, plus RX boards and three sets of crystals. Just need some wire to hook it all up and I will find out whether the idea works.

[wibblywobbly]

I have finally got around to doing the wiring job from hell, it's all been tested and it works, but I can't finish it off properly as I need one more RX18, plus 3 sets of HL crystals. The RX18 just needs plugging in, likewise the crystals.

I puzzled over how I would know that all three boards were active, and then realised that the Leopard has two pairs of rear lights. I left the bottom pair attached to board one, one of the upper ones goes to board two, and the other upper one goes to board three. They all flash when turned on, and the RX18 stays live when the crystal is removed. So all I need to do is make the crystal switching box work and I can make each RX18 active in turn.

If I can't make the crystal switch work, then I can pop crystals in and out of the tx depending on which RX18 I want to use to control various functions. It will be a lot more clumsy, but at least I know that I have a fall back plan.

Crappy pics, but spring is here and the sun is blasting through the kitchen blinds.

[AlwynTurner]

Hi Rob, just a thought but will you need to 'switch on' each rx18 when you start the tank up so they are active when you need them? Alwyn

[wibblywobbly]

You are correct, yes, all three will need power. I can do it by running them all off one switch, or use three seperate ones.

[AlwynTurner]

Sorry Rob I wasn't very clear, when you press the key switch on at the tx you get the tank start up sequence, will you need to do that for each RX18 so they will all be running when you need them? Alwyn

[wibblywobbly]

Hi Alwyn.

The way it works is that I now have all three RX18's wired to one power switch. There are three receiver boards, each with a different crystal number/channel.

A standard HL tx has one crystal socket. I have designed a new mount that allows me to insert three crystals, each on a seperate circuit to the original HL one. So I have three crystals all linked to the one tx crystal socket via a 3 way switch. It is the same as having three tx's each with a different crystal/channel.

I switch on the vehicle.
Crystal 1 switch position 1. Press start button on tx. Wait till light stops flashing on vehicle. Board is now active.
Crystal 2 switch position 2. Press start button on tx. Wait till light stops flashing on vehicle. Board is now active.
Crystal 3 switch position 3. Press start button on tx. Wait till light stops flashing on vehicle. Board is now active.

Now all three boards are live.

I can now switch back to any of the three crystals/channels, and use the RX18 board that is attached to it.
A board stays active even when the channel is not linked to it.
When I switch to a different channel, the tx is only controlling the channel that is currently selected on the tx crystal switch.

I cottoned on to this when I realised that at tank meets, it was common for someone to put their HL tank on a bench, and forget to switch it off. If someone else then fired up their tank using the same channel you would see the tank on the bench suddenly take a lurch off the bench. Catastrophe was never far away....

Switching off the tx doesn't switch off the RX18, its stays active and will respond to a signal from any HL tx that is using that channel.

What could also be done using the same multi crystal adaptor, is to have the entire range of HL crystals plugged into it, with a switch arrangement that enabled anyone of them to be selected, and therefore control multiple tanks at the flick of a switch. A rotary switch would do it.

Back to the build, and it seems that just by painting and adding a few small pieces of styrene to the excavator arm I have reached the threshold of the lift motor. We are only talking a few grams, but when at the lowest point, or resting position, the motor can't lift the arm without human assistance. I will have to redesign the linkage to get more leverage now... grrrr.