RC Locomotive 'Diesel-Electric'

[WickedFog]

@WickedFog What you have”Dennis the Menace” in the US? :0)

You never seen this?

 

[Roog]

I’m not overly happy with the proposed belt route but then I’m only aiming for a top speed of 8 mph, 6 would be more appropriate (realistic)

 

[Roog]

You never seen this?

Ah, now you mention it, yes i had heard about the film, but i guess i was thinking more of the child’s comic not sure when it started probably before the 60’s

Edit: just checked wiki it started 1938, before even I was born :0)

 

[CertifiedMike]

I’m not overly happy with the proposed belt route but then I’m only aiming for a top speed of 8 mph, 6 would be more appropriate (realistic)

View attachment 272237

How about running dual belts?
I think it would be ok as is tho.

 

[Roog]

How about running dual belts?
I think it would be ok as is tho.

Hi @CertifiedMike do you mean two belts and two motors?

 

[CertifiedMike]

Hi @CertifiedMike do you mean two belts and two motors?

From top pulley to axle directly below, then from axle to axle.
It eliminates the 90ish ° bend in the belt.

 

[Roog]

From top pulley to axle directly below, then from axle to axle.
It eliminates the 90ish ° bend in the belt.

Of course, yes I did draw that up early on, but the extra pullies reduced the space between the wheels, that was before I put the truck axle bearings out board of the wheels. Guess that would now be an option.

Like so much in this project I can find out what works and adapt.

The early dual motor design was neat, but when I checked out the cost of all the bits I thought again. One plan was to use geared 540 motors, low cost and the small motors could be concealed within the truck bodies, but I was a bit squeamish about using these more basic motors in a loco build. Cheap to control and to replace if they failed, it was a serious option on the table. Again it could still be done.

Current one motor per truck design is proposed to use Flipsky 6378 skateboard sensored motors

 

[CertifiedMike]

I am curious, have you looked into XC esc? They make esc's for automotive, surgical... as well as for RC. They may have an affordable option for multi-motor applications.

https://www.xc-esc.com



The Flipsky skateboard motor is giant compared to a 540 motor. I am unsure of how to calculate the load requirements for a build like this. I don't know what is sufficient or overkill.

I agree. I think this build will need some pretty robust components. Maybe I have this wrong in my imagination but I see this train as very heavy once its built.



On these Kyosho's, I have 2 different belt systems.
Both start with a motor and pinion driving a spur gear on a (top) shaft. These gears are external.

Internally, 1 car has no additional gears. There are 2 belts that are driven directly from pulleys that are mounted to the top shaft. Those belts drive the differentials directly, diffs drive wheels.

The other set up uses 1 belt in a loop that goes around both front and rear diffs. It goes up over the top shaft too but is on an idler pulley. It free spins on the top shaft.
The top shaft is fitted with the belt pulley and a gear that drives the rear diff. The rear diff is actually what drives the belt system.

I would be happy to try and get some pics so you can see how they are designed.

 

[Roog]

I am curious, have you looked into XC esc? They make esc's for automotive, surgical... as well as for RC. They may have an affordable option for multi-motor applications.

https://www.xc-esc.com



The Flipsky skateboard motor is giant compared to a 540 motor. I am unsure of how to calculate the load requirements for a build like this. I don't know what is sufficient or overkill.

I agree. I think this build will need some pretty robust components. Maybe I have this wrong in my imagination but I see this train as very heavy once its built.



On these Kyosho's, I have 2 different belt systems.
Both start with a motor and pinion driving a spur gear on a (top) shaft. These gears are external.

Internally, 1 car has no additional gears. There are 2 belts that are driven directly from pulleys that are mounted to the top shaft. Those belts drive the differentials directly, diffs drive wheels.

The other set up uses 1 belt in a loop that goes around both front and rear diffs. It goes up over the top shaft too but is on an idler pulley. It free spins on the top shaft.
The top shaft is fitted with the belt pulley and a gear that drives the rear diff. The rear diff is actually what drives the belt system.

I would be happy to try and get some pics so you can see how they are designed.

Thanks for the link @CertifiedMike they have a huge choice. Initially I was recommended the skateboard VESC because traditionally you sit behind the loco and hold the wired controller in your hand plus it offers braking through the VESC functionality. But I’m open to any viable option.

Yeah the Flipsky motor is a bit big, I’m worried about heat dissipation so my choice is 6354 or 6378 either would fit, I am hoping that the bigger diameter outrunners will have good torque. Agreed the 540 is a lightweight by comparison but there would be 4 of them and they would need to be geared too.

My calculations where based on a loco pulling 4 passengers up an incline of 1:100 at about 6 to 8 mph, I would need to check. The answer came out at 600W which to me sounds plausible because the other battery electric locos at the club typically use 4 x 150W motors, it’s just that they have room being 5” gauge loco for big lazy motors.

TBH, the trucks and chassis can be adapted to fit all manor of drive trains, I bought the pullies because it gave me something to work with, they are quite cheap so can be changed if anyone has a better idea, seriously :0)

 

[Roog]

I have a low cost low reving bldc motor which runs my diy battery cylinder mower. It runs at 40v from a matched ESC and was marketed as a scooter motor/esc. It never gets past slightly warm to the touch and easily replaced a 75cc 4 stroke petrol engine with torque to spare. I’d use that if I could think of a way of getting the drive from a big motor mounted in the middle of the body down to the four axles in the trucks.

That would make a bomb proof drive, needing only 2:1 gearing but solving the flexible drive shafts to the trucks felt a bit frail to me. Would only need to get drive to one axle in each truck, then I can link the two axles in each truck with the belt and pullies that I already have

 

[CertifiedMike]

Right, so heat dissipation and back to more fans on the motors. I think large or small, you will need to figure out airflow for the motors.

XC looked interesting to me because they make their own gear, so they know it.
If anyone could help you with multimotor control, seems they would be likely.

The mower motor sounds interesting. A shaft drive train? Is there such a thing?

 

[Roog]

Right, so heat dissipation and back to more fans on the motors. I think large or small, you will need to figure out airflow for the motors.

XC looked interesting to me because they make their own gear, so they know it.
If anyone could help you with multimotor control, seems they would be likely.

The mower motor sounds interesting. A shaft drive train? Is there such a thing?

Yes there’s going to be fans for sure, XC do look interesting even better that they make them I’ll come back to them.

Yes shaft driven locomotives were very common in the UK in the 60’s and 70’s they used telescopic cardan shafts although I wondered whether flexible Bowden cables might work

 

[CertifiedMike]

I was unaware.Those are the same style shafts my Chevy 4x4 had. They worked great in the front end.

My only real experience with cable drive are in old car speedometers and newer window lift motors.

 

[Roog]

Bit of a change in the weather here in the West of England, 21.9C (71.4F) in my shed, gone are the thermal layers.

Today I decided to hold off completing the motor mounts on the trucks, ill wait until i have the actual motors in my hands, and so I started on the chassis rails.

Trimming one end in the mill.

It’s getting a bit cramped in here, but hey I've found a legit use for the adjustable lab/chemistry stand.

Two rails cut to length and square

On to the buffer block, one each end made simply from 2 1/2” x 3/4” aluminium, it’s a bit of a slab, but there’s going to be a fair bit hanging off them. First face off one end.

Cut to length in the band saw, I’m very glad I bought the power saw

Then there were two

As the day goes on my bench reaches ‘critical mess’.

The rails are 1193mm long approximately 3ft 11”

But here they are screwed in place, I’ll save you from watching me cutting all the counter sunk holes and tapping the threads in the aluminium blocks. I amazed they all lined up! With a little help from the Digital Read Out, everyone should have drill/mini mill fitted with one

And on to the plates that accept the trucks, the pivot pin on top of the truck passes through an over sized hole mainly to allow for fore-aft tilting of the trucks, lateral leaning of the chassis will be controlled by ‘waxy’ Delrin plastic pads which will be set into the underside of these plates.

Above, using the DRO to set out all holes from one corner, no marking out required. Image shows chamfering the edges of the holes.

And finally trimming the plates to length.

It’s satisfying to get the full scale of the loco out there, but also a bit of a worry at the mounting size and weight of the thing.

 

[tudordewolf]

I'm very impressed with the amount of labor you're pouring into this, scratch-build modelling & machining from bar stock is stretching the definition of 'hobby.'

My gut feeling on the motor situation is that you're going to want something very tolerant of sustained low-RPM operation.

I am unsure of how to calculate the load requirements for a build like this.

Here's how I would do it - Roog mentioned a goal of 4 passengers up a 1% incline at 6-8mph. Guessing at about 600lbs of load, a 1% incline neatly divides that into 6lbs of pulling force required from the loco, ignoring friction and other losses, but it's enough to work with and then pad later.

Wikipedia says to design for a coefficient of friction of roughly 0.25, which means the locomotive will only be able to pull 1/4 its weight before wheel slip begins. That means the locomotive will need to weigh at least 24lbs, which seems about right for the scale of the project. I'm estimating 60mm wheel diameters, so we'd need about 0.8 N*m of torque at the wheel for that 6lb pull. Accelerating the loco & passengers will take force on top of that, it may even benfit from additional ballast or battery weight in the end.

Next, target RPM - 7mph gives us 1000 RPM wheelspeed with 60mm wheels, eyeballing a 3:1 reduction on the belt for ~3000 RPM at the input pulley. If that's the speed we want the motor to turn at, at 12V, it'll need a kV of around 285. From this we can reverse kT, coefficient of torque, and guess how many amps that'll take. For that kV, it's around 10-15, which sounds right to me, but you'll have to find a matching motor or gear a higher kV motor down the equivelent ratio.

How I'd (maybe) do it: A Hobbywing Gecko Fusion combined with a 5:1 planetary gearbox. That's an all-in-one brushless, sensored ESC with FOC, designed for crawlers, ideal for lots of control at low RPMs, basically perfect for this project. This also simplifies wiring, removing the need for motor ESCs.

I think the Flipsky Skateboard motors would be overkill for this situation, but *could* work, maybe their 140kV motor (on sale!) @ 24V and a current limit programmed into the VESC to prevent wheelslip. I wouldn't worry about heat dissipation with them at all, I don't think they'd ever be loaded over 10% of their capacity before the wheels are spinning- they probably wouldn't even get warm, just my guess. My guess is, wheel-slip is going to limit the overall need for larger motors.

I also considered the options with brushed motors - The trick there would be to pick a high-turn count motor tolerant of running under heavy load. I would go with a 775-size can instead of a 540, they're the predecessor to the 1/8 scale 42xx- inrunner motors, I bet with 775's you'd only need 1 per bogie. They'd be the cheapest option by a lot. You could go quad motor with them, or do 4x 550's, the 55-turn type. Back of the envelope calculations suggest they'd all have enough power to spin the wheels if pushed.

Any progress on the powerplant? I'm itching to take a stab at making a little genny with the 8cc gasser myself.

 

[Roog]

I'm very impressed with the amount of labor you're pouring into this, scratch-build modelling & machining from bar stock is stretching the definition of 'hobby.'

My gut feeling on the motor situation is that you're going to want something very tolerant of sustained low-RPM operation.



Here's how I would do it - Roog mentioned a goal of 4 passengers up a 1% incline at 6-8mph. Guessing at about 600lbs of load, a 1% incline neatly divides that into 6lbs of pulling force required from the loco, ignoring friction and other losses, but it's enough to work with and then pad later.

Wikipedia says to design for a coefficient of friction of roughly 0.25, which means the locomotive will only be able to pull 1/4 its weight before wheel slip begins. That means the locomotive will need to weigh at least 24lbs, which seems about right for the scale of the project. I'm estimating 60mm wheel diameters, so we'd need about 0.8 N*m of torque at the wheel for that 6lb pull. Accelerating the loco & passengers will take force on top of that, it may even benfit from additional ballast or battery weight in the end.

Next, target RPM - 7mph gives us 1000 RPM wheelspeed with 60mm wheels, eyeballing a 3:1 reduction on the belt for ~3000 RPM at the input pulley. If that's the speed we want the motor to turn at, at 12V, it'll need a kV of around 285. From this we can reverse kT, coefficient of torque, and guess how many amps that'll take. For that kV, it's around 10-15, which sounds right to me, but you'll have to find a matching motor or gear a higher kV motor down the equivelent ratio.

How I'd (maybe) do it: A Hobbywing Gecko Fusion combined with a 5:1 planetary gearbox. That's an all-in-one brushless, sensored ESC with FOC, designed for crawlers, ideal for lots of control at low RPMs, basically perfect for this project. This also simplifies wiring, removing the need for motor ESCs.

I think the Flipsky Skateboard motors would be overkill for this situation, but *could* work, maybe their 140kV motor (on sale!) @ 24V and a current limit programmed into the VESC to prevent wheelslip. I wouldn't worry about heat dissipation with them at all, I don't think they'd ever be loaded over 10% of their capacity before the wheels are spinning- they probably wouldn't even get warm, just my guess. My guess is, wheel-slip is going to limit the overall need for larger motors.

I also considered the options with brushed motors - The trick there would be to pick a high-turn count motor tolerant of running under heavy load. I would go with a 775-size can instead of a 540, they're the predecessor to the 1/8 scale 42xx- inrunner motors, I bet with 775's you'd only need 1 per bogie. They'd be the cheapest option by a lot. You could go quad motor with them, or do 4x 550's, the 55-turn type. Back of the envelope calculations suggest they'd all have enough power to spin the wheels if pushed.

Any progress on the powerplant? I'm itching to take a stab at making a little genny with the 8cc gasser myself.

Hey @tudordewolf thanks for your advice, Ihave to confess I ran my calcs through ChatGPT and it put me straight on a few things, but it very much aligns with your thinking. My motor selection is largely down to my web searches when I failed to find a compact geared motor, thanks for your suggestion it will follow this up. Key issue is accommodating the stacked lenght of the motor and gearbox, I will check this out.

As you may have gathered Ihave yet to buy any electrical or RC gear as a had a feeling it might develop. The truck and chassis ‘ design’ LOL are as wide as I could make them to be as flexible to traction solutions as possible. My earlier and favoured inboard bearing truck design was neater but limited motor and gearing placement.

As for the fabrication, I guess that’s the model engineering way, especially if like me you build a model which no one else wants to build, appropriately 90% of the club members run steam locos, and as a result there are lots plans for established designs and castings for big complex parts too, mind you you need deep pockets.

Some progress on the power plant has been made though, after much ‘racking of brains’ I settled on a four stroke petrol engine as the ‘prime mover’. My plan was to buy a low cost used example to experiment with but given the choices I found on eBay and Facebook I gave in and bought a new Honda GX25, bit down on power but adopting my ‘run on battery’ with charge from the generator approach I hope to range extend operation whilst giving the illusion of full diesel-electric operation. The hope is that the Honda will be a more civilised engine and be8ng a four stroke cheaper and more convenient to run.

The tiny generator will appear on these pages sometime this year.

 

[Roog]

Delrin ‘bearing pads’ were todays job. I'm making 1” dia. Buttons with a 10mm locator pin on the back.

It machines very nicely, well behaved

Above I'm parting off the first piece, amazingly three out of the four i made snapped before icould complete the parting operation, lowering the tool solved this on the last one, must remember in future. Here are all four after tidying up the unintended sprues.

And fitted to the chassis

The chassis is sitting high on the trucks, I deliberately left the spacers too long so that i can set the buffers at the correct hight above the rail, ill do that once I've agreed with the club what the preferred buffer height is.

Cylindrical aluminium Spacer is visible in the image below and the gap between the circular plate and the chassis cross member where the delrin pads hold the two apart.

Looking at the image above i might counter sink the holes in the chassis rails and feed the screw in from below, or ….just use shorter screws!

Next job are the buffer beams at each end and the buffers which should be a little more interesting.

 

[Roog]

“Sprung buffers”. The cylinder is made from 1” brass bar with a bore of 12mm and a fixing threaded M8.

Sorry i forgot to take pictures of the cylinder being machined.

Picture above shows me putting the M8 thread on. These gadgets don’t get much use but do come in very handy when they are needed.

Turning it around i drilled a 3mm hole right through to take a silver steel rod with a M3 male thread cut at each end to act as a retainer, to stop the piston falling out!

I made the cylinder bore quite crudely drilling an 11.5mm hole then running a 12mm flat ended milling tool to create a flat bottom to the hole. I have control over the size of the piston so cylinder size isnt critical.

On to the buffer and piston part made in mild steel. The idea is that the steel part should run smoothly in the brass cylinder

Piston is made from 2” dia mild steel bar. A depressing amount of this material needs to be removed from this bar to make the 12mm dia. piston attached to the buffer face all in one piece.

Testing the fit in the cylinder, ‘snug’ I.e. hard to get off!

The piston is bored internally to 8mm to accept the spring and a hole is made at the base, tapped M3 to accept the retainer rod. This was started in the lathe to get it to run concentric to the bore. Finished by hand in the vice.

Here is the piston ‘buffer’ part having been cut and faced off for the next operation

The buffer face is oversized because the loco design requires a specific profile. A trapezoid ?

I elected to cut the faces in the mini mill, this is harder on tooling but saves a lot of rough cuts with a hacksaw. Just touch off the tool at the circumference and makes lots of small passes until you get to the required number on the Digital readout.

Once one side is cut i can use some parallels to set the piece up from this face to cut the other side, well……parallel

Then, set up for one end with a square, bit crude but with care this is adequate for what is essentially a decorative piece, even though they are designed to work.

Next mark up the required angle 24.6 deg! And eye ball this one in the vice. I made a very minor correction using a small mallet after a few passes with the end mill. I just need to make the others the same angle.

And here are the pile of pieces for one sprung buffer.

And assembled, the buffer face is slightly over sized ‘thickness’ for a bit more strength. I guess I could soften the edges.

Would be fun if i only had to make one made over a period of two days, it’s a bit tiresome.
Also i have to concentrate to make the next one handed.

 

[CertifiedMike]

Spring buffers, the cylinder is made from 1” brass bar with a bore of 12mm and a fixing threaded M8.

View attachment 273076

Picture above shows me putting the M8 thread on.

View attachment 273077

Turning it around i drilled a 3mm hole right through to take a silver steel rod tapped M3 at each end to act as a retainer.

View attachment 273078

I made the cylinder bore very crudely drilling an 11.5mm hole then running a 12mm flat ended milling tool to create a flat bottom to the hole. I have control over the size of the piston so size isnt critical.

On to the buffer and piston part in mild steel. The idea is that the steel part should run smoothly in the brass cylinder

View attachment 273079

Piston is made from 2” dia mild steel bar. I depressing amount of this material needs to be removed.

View attachment 273080

Testing the fit

View attachment 273081

The piston is bored to 8mm for the spring and a hole is made to tap the piston M3 to accept the retainer rod.

View attachment 273082

Here is the piston ‘buffer’ part cit and faced off for the next procedure

View attachment 273083

The buffer face is oversized because the loco design requires a specific profile.

I elected to cut the faces in the mini mill, harder on tooling but saves a lot of rough cuts with a hacksaw.

View attachment 273084

Once one size is cut i can use some parallels to set the piece up to cut the other side to the correct depth.

View attachment 273085

Then set up for one end with a square

View attachment 273086

View attachment 273087

Next mark up the required angle 24.6 deg! And eye ball this one in the vice. I made a very minor correction using a small mallet to correct after a few passes with the end mill

View attachment 273088

And here are the pile of pieces for the sprung buffer.

View attachment 273089

And assembled

View attachment 273090

View attachment 273091

Would be fun if i only had to make one
Also i have to concentrate to make the next one handed.

I needed to see the finished, assembled pieces, then review the post, pics all again.
I know this is not the biggest part on this project but seeing it come from stock to reality is beyond impressive!!!

Awesome job! I am blown away!

 

[Roog]

I needed to see the finished, assembled pieces, then review the post, pics all again.
I know this is not the biggest part on this project but seeing it come from stock to reality is beyond impressive!!!

Awesome job! I am blown away!

Thanks @CertifiedMike if I was a bit more organised I would post a picture of the relevant section of the CAD drawing and individual parts drawings followed by a pile of raw materials, and explain myself a little better, then it might flow a bit better.

It is quite fun visualising things from solid and with wickedfog’s help the process was simplified even though it involved starting with more metal. This is one of the few technical elements of this project and was quite fun. Now that I know it works the rest should be a little easier.

I admire the work of YouTubers who set the scene, explain their process and video it in full with each set and lighting planned, They take time to explain the tools they use and the processes, the work they put in is staggering. And to cap it all I notice that their their work space is always clean and organised and their machines, not a mark or pile of swarf to be seen!

I will try to do better. But I can’t promise a clean machine :0)