Powered Bogies

Hi all, just wondering if anyone has any technical drawings of chain driven bogies from a diesel electric/ electric locomotives in 5" or 7.25" and or if anyones made any and has any photos of how they did it?

Anything helps. cheers!

Depends a bit on what motor/drive arrangement you are looking for. The Australian Model Engineering Magazine ran a series (and produced a construction book) on making a 5" gauge model of a New South Wales 422 class loco which i believe has a 12V or 24V electric motor on each bogie with chain drive to the axles. The book is still advertised for sale on their website at https://www.ameng.com.au/85_ame_422_manual.htm . There have also been articles in ME over the years showing pictures of electric model locos under construction, but i don't know if they included drawings. Suggest you have a look in the ME index.

There are commercial products also available using this type of drive, many advertise in ME. Some of these manufacturers also use motors direct geared to the axles similar to a full-size axle-hung traction motor arrangement.

Hope you find something suitable for your needs.

Not sure where you are located, but there are 2 firms in Australia making powered bogies: DNC Technologies and Warrick Sandberg. Both have photos of their powered bogies (2-axle and 3-axle) on their website. Hope this helps.

Just an FYI - the OP did not respond to several forum posters on the first thread he started in April 2018.

Hi Kaleb,

I dont know of any drawings re electric powered bogies but that doesnt mean to say there are none, I just dont of them.

I am in a similar situation, at the moment I am scratch building a 5 inch gauge small electric 0-4-0 but I have also started some sketches for my next project. I fancy a class 22 "Baby Warship" which has twin axle bogies. My thoughts at the moment is 24 volt driving 4 x 250 watt motors, one directly geared to each axle.

Perko mentioned both chain drive and direct gear drive, both of which are available from suppliers and both types work well. I have a leaning towards the gear drives, dont know why really but I seem to prefer gears over chains and sprockets.

What level of power are you considering as this obviously dictates the physical size of the motor and having the space to fit it to the bogie. However with chain drive you can have the motor mounted above the bogie frame which with gears its not so easy. The picture below shows the two motors geared to the axle on my 0-4-0 and these are just can motors but you can see how much space they take up. Should you be considering electric scooter type motors they are considerably larger than the ones shown in the pic.

Cheers

Ron

Edited By Ron Laden on 05/07/2018 14:37:23

Thanks Perko! ill definitely look into the book should be helpful! I'v tried looking over the ME magazines with small results which is why I thought best to ask here!

Hi ron,
I'm more or less trying to make a spin off of a Baldwin 0-4-4-0 diesel-electric switcher which also has twin axle bogies and is why I'm running into the problem of trying to do chain driven bogies since tight space and it'd be very difficult to do gears . As for power for now I'm thinking 24 volt system but due to the size of the locomotive Im still juggling what kind of motor to use since ideally I'd love to have the locomotive be as powerful as I can get it which is why I'm iffy about using several 24v x 250w scooter motors but beggars can't be choosy so its an option!

Hi Jeff, the only reason I didn't reply to the other thread I started was cause being new to the site I wasn't exactly sure how to reply to them as well living in a low service area made it difficult to send the replies though!

thanks all for the replies also!!

There was an article in ME, starting in March 1989 called "Going Electric" by Rex Nicholls, this goes into using old automotive DC generators as traction motors for a 5" Growler with 2 powered bogies.

Ian S C

Hi Kaleb

Like you I would also like my class 22 to have some decent power, at the moment I am thinking a minimum of 1Kw (1.3 hp). I have seen a 5 inch electric loco with 2 x 500 watt motors pull 10 people with no problems, I like the idea of having the ability of carrying a good number of passengers.

I mentioned 4 x 24volt/250watt motors but I have also considered 500 watt motors, one for each bogie. I have thought of a few permutations regarding the drive. Single motor driving one axle with a chain or belt drive to the second axle, single motor driving both axles with a single chain drive direct from the motor, single motor driving both axles via gears. Also both bogies each having a single motor driving one axle via gears. I know that most powered bogies have all the wheels driven and obviously that is good for grip and traction. I cant see why a single axle drive on each bogie wouldnt work, I think it would. Depending on the build a 5 inch 24 volt twin bogie loco is going to be somewhere in the region of 60-70kgs so it wouldnt lack weight.

You mention 5 inch or 7.25 inch, obviously 7.25 inch would allow you quite a bit more space to fit everything in.

It will be interesting to know how you get on.

Regards

Ron

Edited By Ron Laden on 07/07/2018 10:22:23

Regarding power, don't forget that 1HP is quite a lot of power for a small loco. I've been on a horse-drawn tram weighing 3 tons and carrying a load of 22 passengers which was pulled quite comfortably by a single horse. Power needed to accelerate is much greater than that needed to sustain speed, particularly at less than 15km/hr. The main problem will be traction. A loco weighing 100kg on 4 axles with all wheels driven will have a maximum drawbar pull of about 35kg regardless of how much power it has. Any more than that and you exceed the adhesive capacity of steel wheel on steel rail.

1 man-power is equivalent to about 1/5HP and a moderately fit person can comfortably push a couple of riding cars loaded with a dozen people at a fairly fast pace.

Just food for thought .

Hi Perko,

I could be wrong but if we take 1 HP as approx 750 watts an average draft horse is capable of 15HP and a reasonably fit person capable of 4HP but as I say I could be wrong. I appreciate that more power is required to accelerate than to maintain a rolling speed but all things considered I think if you are aiming at pulling a dozen people with no issues then 1HP (750watts) would be about right.

regards

Ron

I wouldn't want to meet the man who could develop 4 HP, even a very fit cyclist can only manage about 1/2 HP over any length of time, possibly twice that for very short bursts. Similarly, one horse can develop on HP, actually a bit more as James Watt understated horses to make his engines sound more powerful.

Sorry...decimal point...?, I meant to say 0.4 HP for a fit person.

Hi Ian,
I'm looking into where I can get that issue currently! Thank you

To Ron and Perko, my only wonder between 250w and 500w is which would be more economical on power having 4 x 250w or 2 x 500w or the same? I don't claim to be any kind of expert on electric motors after all. Assuming one 24v 500w motor gives out ~.65hp thus two would give out 1.3hp, if that can take about 10 passengers would that then mean only one 24v 500w motor can take about 5 passengers? If so then could that be an option due to my size constraints to only have one 24v 500w motor and just make that power both bogies through a driveshaft type construction even though that would complicate things significantly or even a 24v 750w motor with the same driveshaft concept? what do you guys think is that an option? or any better ideas?
cheers, Kaleb

Hi Kaleb,

I am no expert either far from it, the 0-4-0 chassis I am building is my first attempt at an electric loco. I tend to go by the basic sums (and hope they are correct), the advice the guys have given me here and what I,ve seen and read, plus a bit of gut feel.

The 4 x 250 watt and 2 x 500 watt "should" draw about the same in power, in a 24 volt system around about 40 amps. I would think that a single 500w motor would handle 5 passengers and probably more but Perko will probably be able to confirm that. I have been told that the 4 x 12 volt motors (total 260 watts) I am using on the 0-4-0 should cope with 3 or 4 adults but the proof will be in the pudding..?

I am aiming at 6 to 7mph top speed which gave me a gear ratio of 6.25 motor to axle, but again there is a bit of hit and miss here as the motors I have run faster than what their spec says. This is unloaded though so again a suck it and see scenario.

I can see a single motor using drive shafts working ok but as you mention it is a more complicated and of course you have to allow for the pivot of the bogies each end.

Regards

ron

Having absolutely no experience of powered bogies ... May I just suggest that, to minimise side-loads on the gear-train, three small motors clustered around the large gear would seem ideal; and might form a very compact module.

MichaelG.

Kaleb,

Something I forgot to say, I have been told that the claimed power for some of the motors is not correct. The quoted wattage is often higher than the motor actually produces, apparently it is the way they are measured which gives true or false readings. I read of a 24 volt 350 watt scooter motor (Chinese) that a guy had correctly tested and it only produced 240 watts, so a third less than claimed.

I cant confirm if this is true but it could put yet another complication into the equation. At the end of the day though all we can do is trust what is quoted is somewhere close.

Ron

Edited By Ron Laden on 08/07/2018 10:52:36

It depends on whether you measure the power into the motor(high), or the power output at the shaft, that will be quite a bit less.

Ian S C

Sorry to admit i'm no expert in these matters, my only knowledge is what i learnt doing engineering at uni too many years ago. There is a download on the SMEX site to calculate rolling resistance for a train based on various inputs, which can be used to estimate the power required to pull that train. As an example, a loco weighing 100kg towing a train consisting of 2 wagons each weighing 100kg, with each wagon carrying 6 adults weighing 80kg, at 10km/hr up a 1:50 grade would require a drawbar pull of about 27kg assuming relatively free-rolling wheelsets. The maximum drawbar pull available from our 100kg loco would be about 35kg so the train is within the loco haulage capacity. The power required to accelerate our train to that speed is a different calculation that is a bit more complex. Basically, more power = faster acceleration, up to the limit of our drawbar pull which is a function of loco weight and the adhesion factor for steel wheel on steel rail. I would look at what others have used in practice and found sufficient.

While unfamiliar with the article mentioned above there were others from the 1970s onwards that suggested the use of three brush car dynamos converted into traction motors. Two brush dynamos are far less easy to use as motors.

Three brush dynamos were replaced on cars by the more efficient two brush types from the late 1930's and were almost totally extinct by the 1950s. However due to the fact that cars tended to be kept longer then, the older kind of dynamos were still available from scrapyards in the 1970s and eighties.

I suspect that today you may find it harder to source any type of car dynamo, let alone the three brush type except as a very expensive spare part for a classic car. The scrap car trade has shrunk, as has the car electrical spare part business.

Check carefully what the article asks for, but my gut feeling is that advances in motor technology, particularly in permanent magnet motors, my mean that old car parts are not the best way to go.

The way electric motors are specified isn't standardised at all well. In theory, Horse Power is a measure of output, yet I've seen it used to specify input. Watts can be used to measure both input and output powers but many motor plates don't bother to say which they mean. Even when a plate says it's output power, rarely do you get to see the graph explaining exactly how to load the motor to achieve that output.

I refer to this link whenever I need reminding that electric motors are complicated at the best of times, and their performance across a range varies. It varies so much that particular constructions are used meet particular purposes.

The example below graphs torque and power against speed. It shows power output on this motor peaks mid-rpm and that torque (ie turning power) peaks at low rpm. Note power output is a hill shaped curve and than torque is a straight line decreasing with rpm. And that the graph says nothing about efficiency, except many motors are most efficient at maximum power output.

High torque at low-speed is good on a railway because it helps the engine pull away from a stop. Steam and electricity both deliver considerably better starting torque than internal combustion. At higher speeds electricity outperforms steam because it can rotate an armature smoothly compared with the hammer action of a reciprocating engine.

Once a train is moving at a steady speed it only needs enough power to overcome the rolling resistance, With decent bearings and good track rolling resistance will be quite low, even if the train is loaded with chubsters. You don't need a lot of power. Much more is needed to accelerate the train or to pull a load up an incline. Where you run the engine matters: a club with lots of flat straight track requires less of the engine than one with lots of bends and hills.

The other major factor is how well the driving wheels grip the rails. Apply too much power when accelerating, or attempt to climb an excessive hill, and the wheels will spin. Once wheels start spinning, power and torque matter not one jot.

Getting an model loco 'spot on' is a challenge. The design should balance weight, power and torque. 'Bigger is better' may not be the answer. Powerful motors imply a heavy locomotive to get the necessary adhesion. Heavy locomotives damage the track more than light ones, and you have to lift them! Powerful motors imply big batteries, stronger chassis, higher all-round costs, and limited running time. The good news is that others have been there first, successfully using powers as low as 80W to pull a driver and a couple of passengers. My feeling is 2x500W is over the top unless you intend running a fast stop-start service like a tube train, or to pull very heavy passenger loads, or are going for speed records.

There are so many variables in the design worrying about what someone else said about a motor is likely a waste of time. Within reason I don't think the power is critical and will be very surprised if what you build doesn't perform.

Dave