Powered driving truck

[darrene]

After starting a second tender-powered steam outline project and conscious of the amount of duplication I was introducing, I wondered if it might be wiser to put the motive power and control into a drivng truck instead, which could then be used for any such project. it has the merits of avoiding the costs and maintance involved in duplication, keeps the weight of the locos down and means the implementation only needs to be solved once.

Enter the powered driving truck project.

Using an RoR wagon sourced from Mr Cro, I set about modifying it as subtly as possible to provide the power solution for both the Princess Royal and Mallard projects.

The wagon was well suited as it had plenty of interior space to house everything and would not require very much in the way of alteration.

I treated it as two sub-projects. First was the body and electronics, second was the chassis and drivetrain.

The body was already internally subdivided into three sections. I chose to use the forward section to house the drive controller and front bogie power distribution, the mid-section to contain the batteries and the tail section to house the rear bogie power distribution.

Sadly, the 50ah leisure batteries I had and was intending to use in the truck were too tall to fit the body. Gargh! Lowering where they sat was the obvious answer and had the added benefit of keeping the centre of gravity low. I decided to cut a hole in the floor of the centre section allowing the batteries to sit a couple of inches lower, on the steel chassis frame rather than the wooden floor. This also allowed the body to be easily removed from the chassis without disturbing the batteries. A stretcher bar was relocated from above the chassis rails to beneath them, to keep the frame there flat.

A 4QD DNO controller, power monitor shunt and MCB were put into the front compartment. The MCB is installed downward-facing such that it can be activated from underneath and behind the front buffer beam - I wanted to alter the exterior as little as possible. One pair of controller outputs (Red and Black) goes to a Wago connector for the front bogie, the other pair (Blue and Yellow) go to a Wago connector in the rear compartment for distribution to the rear bogie. The simple flip-up latches make disconnection easy and are all that are required to remove the body.

The connector for the 4QD controller on the front panel is the only visible external change. I'm thinking I'll blacken the metal plating on it to tone it down a bit more.

Darren

[darrene]

The chassis/drivetrain was a harder project, mainly because the packaging envelope available was smaller

I am reusing the 150W Parvalux motors I'd originally used in the tenders and am using the same axle-hung brackets. One motor per axle, so 4 driven axles in all and a total of 600w

Being on pivoting bogies, the motors need to sit vertically above the axles for the bogies to retain enough articulation. Previously the bogie profile sat entirely beneath the chassis frame. Now the motors extend vertically into the frame space and ultimately restrict some amount of bogie rotation but the amount left seems to be a fair bit more than what the locos would be able to manage.

This picture shows the general arrangement. Note the motors are sitting far closer to the central mount than they will normally as the top motor stay bracket isn't in place. This holds them further away.

They also fit for height beneath the body, despite looking as though they don't!

I was hoping to keep the original bogies otherwise intact. Unfortunately I just couldn't get the sizings to work with the original wheels which are just too small in diameter. Their diameter determines the maximum size of the spur gear on the back of them and this resulted in the pinion gear on the motor being too far away to mesh.

The motor couldn't be moved any closer to the axle, there was no space on the bracket for a layshaft gear and chain drive could prove troublesome to install and maintain.

In the end I cut my losses, pressed the wheels and bearings off the axles and installed 4" diameter wheels instead. These could accomodate the 90t gears which I already had from the tender installation and provided a decent gearing with the 12t pinions already fitted to the motors. The oilite bushes I had needed reaming out slightly to accomodate the RoR axles but otherwise everything fitted

The next step is to finalise and fabricate the motor top support brackets, wire up the motors and give it a test run.

Darren

[darrene]

A quick bench-run of the setup to check everything works. Sod's law dictated that I guess-mounted the bogies 360 degrees out as backwards is forwards and vice-versa.! That's a very quick job to change though.

The motor on the fourth bogie was left disconnected intentionally as I haven't completed the top stay bracket for that motor.

I'm printing a case for the Renogy display which gives a readoout of voltage, current and calculates remaining runtime. That will sit in the front compartment and can optionally be mouted on an angled bracket that slips onto the front lamp-iron.

Once the last motor is plugged in, I'll try a track-test sitting aboard it and think I might wire in an R/C receiver and interface for a bit of fun in the garden!

Darren

[darrene]

The first seated run on track of the powered driving truck. In a word, brilliant. In two words, really brilliant!

It was a simple down and back but the truck is super smooth and seems to have plenty of speed and torque.
The next test be running some long distances down at the club track to see how it handles pointwork, curves, how long the batteries last and whether or not it remains issue free.

Darren

[barlowworks]

You could get knicked for speeding on that, quite a turn of speed. Nice job,well done.

Mike

[andyhigham]

It would be very useful at IMLEC ;-)

[cplmickey]

Lovely job. Very smart.

[dhamblin]

Nicely done Darren, hope the next phase of trials go as well.

Regards,

Dan

[choochooenthusiast]

You’ll be able to hit 126 when your A4 is in front of that

[steamer5]

Hi Darren,
Nice work! I have the same controller, only issue ive had with it when some idiot.....me ...... cranked the controller way up from a standing start on an uphill grade & had a resister pack in! Contacted 4QD & purchased & installed a replacement which is self resetting, no issues since...oh haven't repeated the crank it on!
Reguards how long the battery will last, Toby has 2 x 40 amp marine batteries the motor is about 1/2 your total, he is speed limited to 13 km/hr via the gearing, & i can play...errr... run for the day. As you are not on the move the whole time, a 6 hr day no problem....IF your batteries are in good condition!
Looking forward to how you tests on your club track go

Cheers Kerrin

[andyhigham]

Does the controller have the facility to program in an acceleration ramp time? I know the pro series do.
You could then whack the pot to full and the motors would accelerate at the rate set by the ramp

[steamer5]

Hi Andy,
Best I go check !! I know it has a 1/2 speed for reverse as i set that.
Thanks for the prompt!

Cheers Kerrin

[Jim]

Jan 27, 2023 19:55:49 GMT steamer5 said:

Hi Darren,
Nice work! I have the same controller, only issue ive had with it when some idiot.....me ...... cranked the controller way up from a standing start on an uphill grade & had a resister pack in! Contacted 4QD & purchased & installed a replacement which is self resetting, no issues since...oh haven't repeated the crank it on!
Reguards how long the battery will last, Toby has 2 x 40 amp marine batteries the motor is about 1/2 your total, he is speed limited to 13 km/hr via the gearing, & i can play...errr... run for the day. As you are not on the move the whole time, a 6 hr day no problem....IF your batteries are in good condition!
Looking forward to how you tests on your club track go

Cheers Kerrin

Hmmm now you've given me a clue as to why my rail motor lost power following a driving truck derailment at the foot of a grade. With the driving truck rerailed I made a start up the grade with..from memory the throttle almost fully open. The loss of power meant I had to more or less 'scooter' up the grade until it levelled out and power returned and all was well.

Jim

[steamer5]

Hi Jim,
Had the same issue to get back around to take Toby off the line! To be fair it was also a hot day which likely didnt help.

Cheers Kerrin

[darrene]

Thank you for the kind words. I think I too will need to tweak the ramps slightly once I've got the load of the  loco and stock.

Yep, the DNO controllers do have the adjustable acceleration and deceleration ramps.

The default acceleration ramp is a 2 second accleration-to-maximum time. Turning the pot clockwise increases the time taken to reach maximum speed, anticlockwise decreases the time taken.  (NOTE: Increasing the acceleration time too much may cause the acceleration time to be controlled by the current limit and motor load, rather than the controller.)

The deceleration ramp is set by default to 3s which is half-setting. Usually a lower setting (anticlockwise pot adjustment) is preferred for the deceleration ramp compared to the acceleration ramp. (NOTE: setting the time too low (anticlockwise)  may cause the relays to short the motor before the regenerative breaking has completed, jerking the loco to a stop)

The adjustment pots are in the bottom left of the picture:

Darren

[darrene]

Another bench test showing the new quick-detach displays for power and speed

Darren