Building a radio controlled (electric) traction engine

What is your latest project?
User avatar
tom_tom_go
Driver
Driver
Posts: 4824
Joined: Wed Feb 23, 2011 3:08 am
Location: Kent, UK
Contact:

Re: Building a radio controlled (electric) traction engine

Post by tom_tom_go » Thu Apr 26, 2018 7:40 am

A traction engine popping wheelies, very cool.

I like it Greg, the speed changes have improved it's running.

Can you not fit a speaker in the roof of the cab?

User avatar
gregh
Trainee Driver
Trainee Driver
Posts: 566
Joined: Sun Apr 01, 2018 5:44 am
Location: Sydney, Australia
Contact:

Re: Building a radio controlled (electric) traction engine

Post by gregh » Thu Apr 26, 2018 7:45 am

FWLR wrote: Thu Apr 26, 2018 7:36 am Loved the video Greg, it was a bit steep that hill…. :)
Think the wheels need a pivot of some kind to keep them both on the ground on uneven surfaces don’t you think. In the full scale ones they have them don’t they.. :thumbright:
It was working fine before I added the chains.
I've loosened off the pivot screw and will see tomorrow if that helps or whether I need to loosen the chains as well. I did try today with both chains loose and I was surprised that it ran straight BUT everytime it hit a small bump, the steering wobbled around and then came back straight - a very unprototypical look, so I tightened them again.
Maybe if I loosen just one side.

As to the hill - the wheel was slipping on the axle which may have contributed to the 'fail to proceed'.
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm

User avatar
gregh
Trainee Driver
Trainee Driver
Posts: 566
Joined: Sun Apr 01, 2018 5:44 am
Location: Sydney, Australia
Contact:

Re: Building a radio controlled (electric) traction engine

Post by gregh » Thu Apr 26, 2018 7:58 am

tom_tom_go wrote: Thu Apr 26, 2018 7:40 am Can you not fit a speaker in the roof of the cab?
I have recorded that sound on the video onto a 20 sec sound recorder card. I only have a 25mm mylar speaker to test it, and it was just hopeless. I could fit two, 40mm mylar into the roof but I have used them before in a little diesel and the volume is so low that you have to be up close and personal to hear it.
I don't have the 'depth' under the roof to hide a 'real' speaker, although I suppose I could hide it in a box that stuck down.

And if I do put them in the roof, I have to get the wires up there somehow. The roof support tubes are hollow but I want the roof the pull off, so if I run any wires that will be difficult.

I need something to remind me that it is turned on too, but the sound card would only play while running so that won't help. I need a light.
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm

User avatar
FWLR
Driver
Driver
Posts: 4262
Joined: Sat Aug 05, 2017 9:45 am
Location: Preston, Lancashire, UK

Re: Building a radio controlled (electric) traction engine

Post by FWLR » Thu Apr 26, 2018 8:00 am

And loosening the chains would help I’am sure Greg. They hang down on the full scale one’s on one side slightly so has to compensate for any rough roads. If you see one been driven, you will see the driver constantly adjusting the steering wheel to keep the engine running straight… :thumbright:
412In_Burrell_Traction_Engine_Green_7.jpg
412In_Burrell_Traction_Engine_Green_7.jpg (333.21 KiB) Viewed 5657 times

User avatar
philipy
Moderator
Moderator
Posts: 5033
Joined: Sun Jan 30, 2011 3:00 pm
Location: South Northants

Re: Building a radio controlled (electric) traction engine

Post by philipy » Thu Apr 26, 2018 8:25 am

I think the reason why one side is slack on the real thing is that the steering chain is continuous and wraps several times round a horizontal rod/pulley, which rotates one way or the other to change direction, so its always tight on the side into which it is turning. Having both sides slack will always tend to create a self centring effect, assuming they are both the same length, since the weight trying to drop down on both sides will be the same.

Having said all that, the actual run is very impressive, but won't leave much brain power spare to run trains as well!
Philip

User avatar
Lonsdaler
Driver
Driver
Posts: 1226
Joined: Tue May 20, 2014 9:50 am
Location: North Yorkshire

Re: Building a radio controlled (electric) traction engine

Post by Lonsdaler » Thu Apr 26, 2018 9:52 am

You could try and pick up a laptop speaker - generally compact, but of better quality than the mylar 'tranny' types.
https://www.ebay.co.uk/i/231573236571?c ... 342&crdt=0
Phil

Sporadic Garden Railer who's inconsistencies know no bounds

My Line - https://gardenrails.org/forum/viewtopic ... 41&t=11077

User avatar
gregh
Trainee Driver
Trainee Driver
Posts: 566
Joined: Sun Apr 01, 2018 5:44 am
Location: Sydney, Australia
Contact:

Re: Building a radio controlled (electric) traction engine

Post by gregh » Thu Apr 26, 2018 11:00 am

Lonsdaler wrote: Thu Apr 26, 2018 9:52 am You could try and pick up a laptop speaker - generally compact, but of better quality than the mylar 'tranny' types.
https://www.ebay.co.uk/i/231573236571?c ... 342&crdt=0
Thanks for that idea. I had never thought about laptop speakers being small.
I've ordered some similar ones already.
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm

User avatar
Lonsdaler
Driver
Driver
Posts: 1226
Joined: Tue May 20, 2014 9:50 am
Location: North Yorkshire

Re: Building a radio controlled (electric) traction engine

Post by Lonsdaler » Fri Apr 27, 2018 9:59 am

gregh wrote: Thu Apr 26, 2018 11:00 am
Lonsdaler wrote: Thu Apr 26, 2018 9:52 am You could try and pick up a laptop speaker - generally compact, but of better quality than the mylar 'tranny' types.
https://www.ebay.co.uk/i/231573236571?c ... 342&crdt=0
Thanks for that idea. I had never thought about laptop speakers being small.
I've ordered some similar ones already.
Not really my idea, but you're welcome. I think it is 'Chuffed to Bits' who supplies his sound cards with a laptop speaker as standard. :)
Phil

Sporadic Garden Railer who's inconsistencies know no bounds

My Line - https://gardenrails.org/forum/viewtopic ... 41&t=11077

User avatar
tom_tom_go
Driver
Driver
Posts: 4824
Joined: Wed Feb 23, 2011 3:08 am
Location: Kent, UK
Contact:

Re: Building a radio controlled (electric) traction engine

Post by tom_tom_go » Fri Apr 27, 2018 11:06 am

I use Peter Spoerer for laptop speakers. You need to be careful with buying small speakers on eBay due to quality and if it comes with a well made back box for reverb:

http://www.peterspoerermodelengineers.c ... fo.php?p=4

User avatar
gregh
Trainee Driver
Trainee Driver
Posts: 566
Joined: Sun Apr 01, 2018 5:44 am
Location: Sydney, Australia
Contact:

Re: Building a radio controlled (electric) traction engine

Post by gregh » Sat Apr 28, 2018 1:14 am

tom_tom_go wrote: Fri Apr 27, 2018 11:06 am I use Peter Spoerer for laptop speakers. You need to be careful with buying small speakers on eBay due to quality and if it comes with a well made back box for reverb:

http://www.peterspoerermodelengineers.c ... fo.php?p=4
Well I've ordered some cheapies, so I'll report how they perform when they finally arrive. I'm not concerned if I've wasted a couple of dollars with free postage from China. AS I've said above, I doubt I'll waste any more time on the traction engine getting sound in it anyhow.
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm

User avatar
steamer68
Trainee Fireman
Trainee Fireman
Posts: 208
Joined: Tue Nov 28, 2017 11:33 am
Location: Bishop Auckland, UK

Re: Building a radio controlled (electric) traction engine

Post by steamer68 » Sat Apr 28, 2018 3:02 pm

Greg a fantastic job on your radio controlled traction engine and I really like the sounds. :thumbright:
Regards
Kevin

User avatar
gregh
Trainee Driver
Trainee Driver
Posts: 566
Joined: Sun Apr 01, 2018 5:44 am
Location: Sydney, Australia
Contact:

Re: Building a radio controlled (electric) traction engine

Post by gregh » Mon Apr 30, 2018 12:54 am

As soon as I started testing I noticed an intermittent control problem. I'm using a picaxe to control the motor speed, direction and steering. But there is some interference which causes the picaxe to stop and restart its program.
I am sure this is what is happening as if it’s in reverse at the time, when I restart it is in forward. This can only happen in the startup part of the program. The engine restarts when the throttle is returned to stop.
It happens mainly at full throttle (which is only about 55% of battery volts), but can happen at anytime, any direction and on straight or curves.
It doesn’t seem to do it on the bench, even when I put pressure (load) on the wheels.

After much investigation using my oscilloscope, I have managed to overcome the problem (I hope - who knows with intermittents?). But I don't understand why.
It seemed to have something to do with 400mV dips on the 5V caused by the steering servo which seems to take spikes of 1 amp when it's moving. I won't go into all the things I tried, I ended up feeding the 5V to the picaxe and Rx via a diode and then a 47,000uF capacitor. I only had a 'normal' diode so that's a 0.7V drop to the picaxe, but I'll get a Schottky type later.

Just for info, this is the voltage trace before I 'fixed' it. The fuzzy line is a 100mV peak-peak exponential type wave caused by the RX (why? who knows?). The dips are 400mV due to servo current. With the diode and supercap, these are both halved.
cro4 servo interference.png
cro4 servo interference.png (118.04 KiB) Viewed 5448 times
And this is the circuit:
TE circuit.jpg
TE circuit.jpg (76.6 KiB) Viewed 5446 times
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm

User avatar
FWLR
Driver
Driver
Posts: 4262
Joined: Sat Aug 05, 2017 9:45 am
Location: Preston, Lancashire, UK

Re: Building a radio controlled (electric) traction engine

Post by FWLR » Mon Apr 30, 2018 7:00 am

All well beyond me Greg, but I’am glad you have it sorted. :thumbright:

User avatar
ge_rik
Administrator
Administrator
Posts: 6497
Joined: Sun Oct 25, 2009 10:20 pm
Location: Cheshire
Contact:

Re: Building a radio controlled (electric) traction engine

Post by ge_rik » Mon Apr 30, 2018 7:06 am

I admire your tenacity, Greg. I must admit that I'd have assumed there was a dodgy connection if it was happening in the field but not on the bench, but the oscilloscope trace suggests something else is going on. Presumably, as the difference between this program and your usual one is the addition of the steering routine and circuitry, then it makes sense that this is where the glitch is happening. But as to why ....... ?

Rik
------------------------
Peckforton Light Railway - Blog Facebook Youtube

User avatar
tom_tom_go
Driver
Driver
Posts: 4824
Joined: Wed Feb 23, 2011 3:08 am
Location: Kent, UK
Contact:

Re: Building a radio controlled (electric) traction engine

Post by tom_tom_go » Mon Apr 30, 2018 9:35 am

Surely there is a faulty component causing this?

Southern188
Cleaner
Cleaner
Posts: 40
Joined: Thu Jan 11, 2018 8:37 am
Location: Dorset

Re: Building a radio controlled (electric) traction engine

Post by Southern188 » Mon Apr 30, 2018 9:39 am

I had a similar problem recently, the DFPlayer sound card I was playing with interfered with another 5 volt circuit (not the processor). I solved it as you with a schottky diode and capacitor. I also changed the layout to ensure the 0v and 5v lines of the offending device went directly to the regulator rather than being at the end of the power lines.

Servos are electrically noisy. I use the Tower Pro SG90 on my steam train and they produce 500mv of noise on the 5v line but the processor I use is 3 volt so is well protected by it's internal regulator.

You have a 0.1uF capacitor in your circuit diagram, ensure you have one as close to the processor power rails as possible.

Great to see someone else with an oscilloscope. My 1970s Telequipment D61a is still working well!

Michael

User avatar
gregh
Trainee Driver
Trainee Driver
Posts: 566
Joined: Sun Apr 01, 2018 5:44 am
Location: Sydney, Australia
Contact:

Re: Building a radio controlled (electric) traction engine

Post by gregh » Mon Apr 30, 2018 11:55 am

Southern188 wrote: Mon Apr 30, 2018 9:39 am I had a similar problem recently, the DFPlayer sound card I was playing with interfered with another 5 volt circuit (not the processor). I solved it as you with a schottky diode and capacitor. I also changed the layout to ensure the 0v and 5v lines of the offending device went directly to the regulator rather than being at the end of the power lines.
Not quite sure what you're saying, but my servo has separate power wires direct from battery and the picaxe+Rx are fed along another pair

Servos are electrically noisy. I use the Tower Pro SG90 on my steam train and they produce 500mv of noise on the 5v line but the processor I use is 3 volt so is well protected by it's internal regulator.

You have a 0.1uF capacitor in your circuit diagram, ensure you have one as close to the processor power rails as possible.
Yep, It's right at the picaxe terminals

Great to see someone else with an oscilloscope. My 1970s Telequipment D61a is still working well!

Michael
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm

User avatar
gregh
Trainee Driver
Trainee Driver
Posts: 566
Joined: Sun Apr 01, 2018 5:44 am
Location: Sydney, Australia
Contact:

Re: Building a radio controlled (electric) traction engine

Post by gregh » Mon Apr 30, 2018 12:10 pm

tom_tom_go wrote: Mon Apr 30, 2018 9:35 am Surely there is a faulty component causing this?
Always a possibility, but since I have got rid of the problem (fingers crossed) with the mods I made, it seems less likely to be a component.
What component could it be? I've tried different picaxe. I've checked that other Rx of the same type cause the same modulation on the battery. I hope it's not the servo as it's glued in. And I'm happy that the battery doesn't have too much internal resistance. I might try and measure another servo's current just for future reference.

One thing I do wonder about is the picaxe - datasheet says it operates internally on 3.3V but has a regulator so can operate from 5V and it selects automatically. I just wonder what it does as the voltage dips. Does it have trouble as the voltage falls and its internal regulator dropout voltage comes into play and that causes a restart?

Anyhow, while it continues to work, I ain't touching it.
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm

User avatar
tom_tom_go
Driver
Driver
Posts: 4824
Joined: Wed Feb 23, 2011 3:08 am
Location: Kent, UK
Contact:

Re: Building a radio controlled (electric) traction engine

Post by tom_tom_go » Mon Apr 30, 2018 1:22 pm

I agree, if it ain't broke don't fix it but having myslef had all sorts of odd issues with budget servos in the past I reckon it's that.

User avatar
gregh
Trainee Driver
Trainee Driver
Posts: 566
Joined: Sun Apr 01, 2018 5:44 am
Location: Sydney, Australia
Contact:

Re: Building a radio controlled (electric) traction engine

Post by gregh » Tue May 01, 2018 12:59 am

tom_tom_go wrote: Mon Apr 30, 2018 1:22 pm I agree, if it ain't broke don't fix it but having myslef had all sorts of odd issues with budget servos in the past I reckon it's that.
Just to try and convince myself, I took a similar 'cheap blue' servo and had a look at it's waveforms.

Fed from my bench supply, it caused a 250mV dip in the supply every time it moved ( in engine I had 400mV).
I put a 1 ohm resistor in series and measured it's voltage drop= amps, and it takes a spike of 500mA each movement, with no load on the servo. I had estimated 1A in the engine, assuming 0.4 ohms. So I tested the battery and found its internal resistance incl the polyswitch is 0.6 ohms. So the servo would cause a 300mV dip calc compared to my measured 400mV. These are all close enough for me to say that I don't think the servo is faulty.
It all goes down as experience - running a servo takes big current spikes that have never been a problem for me before as I have always used a regulator for the picaxe supply.
Greg from downunder.
The Sandstone & Termite's website: https://members.optusnet.com.au/satr/satr.htm

Post Reply

Who is online

Users browsing this forum: No registered users and 4 guests