Science Buddies: "Ask an Expert"

How to make a trolly bus.I would appreciate if u could give me step by step imstructions along with materials required.how does it work ?? Can u give me structure picture.I really want to do this for my project .thanks in advance

Hi Ru8bin-

By 'trolley bus', do you mean the electric buses that have contact arms reaching up to overhead wires? Those are commonly found in large cities where they reduce pollution by running entirely on electricity. This is an old one in Los Angeles, CA for anyone else reading this that doesn't know what they look like.


I can tell you how they work. At it's heart, it's an electric bus in the same sort of way that an electric car works. It has electric motors instead of gas or diesel engines. Unlike an electric car though, it has no batteries. To get power, it has to run underneath a grid of electric wires strung up by the city.

The wires are attached to poles next to the street and carefully stretched and mounted so that they are the same width apart and same height over the road (usually about 18 to 20 feet). The pair of wires is insulated from the poles and provides about 500 to 600 volts to the bus below. The bus has a pair of arms that use springs to push firmly up on the wires, making contact and providing a current path to the bus electronics. A conductive wheel (sometimes just a metal shoe) at the end of the pole rolls along the wire.

From there, wires bring the power into the bus and the operator controls send that to the motors.

Building your own would be fun. For starters, you need to make a model road of some kind. Pick a scale that's reasonable and imagine a model bus that size. a 1:12 scale would mean that for every 1 foot in real life, your model would be 1 inch. 1:24 is a very popular scale and you can buy all sorts of pre made model buses in that size. A bus that normally stands 10 feet would be 5 inches tall. At that scale, the wires 18 feet over the road surface would be 18*12/24, or 9 inches over the road surface. You'll have to invent a cool method of suspending the wires at that height and keeping them inserted from each other and the poles. The bus will have to have a motor stuck in it unless you can find a toy bus with a motor already in place. Whatever voltage that motor needs (it might be 3 to 6 volts perhaps), that's what you'd energize your wires with. Don't worry about safety because a few volts from a battery isn't dangerous. Put some spring loaded arms on top of the bus.

You might actually find kits in model railroad scale for a project like this. Model railroaders love to make tiny replicas of all things in cities and I know that electric trolleys are often pet projects. If you can't find a model railroad kit you'll be building this with your own design and parts that you find yourself. It will be a little ambitious so be sure to start early and leave yourself plenty of time.

Howard

hello howard
thank you i got the concept but can you please tell me how can i move the trolley in my desired location.I mean for example :I want to move the bus right when there are 3 directions ahead.It may be difficult to find the kit so Can you describe all the process along with materials required,etc.
Many many thanks

Hi again Ru8bin-

I found this discussion on an old model railroading forum:

I posted this on the SEPTA forum because of their use of both trolleys and trolley buses (err, sometimes).

I thought of this question (again) while riding the 102 home from work on Monday. I noticed at Drexel Hill Jct a box at operator height with buttons marked Media and Sharon Hill. Presumably the operator presses this button to indicate which route he is taking thus changing the signal/switch or some such combination. This made me think back (via a roundabout thought process!) to trolley poles and how they negotiate diverging routes.

Obviously pantographs contact the bottom of the wire and thus don't have to really negotiate divergances. But how do trolley poles such as on the city trolleys and the trolley buses know which route to take? Does the turning of the vehicle "pull" the pole onto the correct wire?

Simple question, perhaps, but I've always wondered how it worked.

Thanks,

Bob

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Postby xxxxxxxxxxxx » Wed Oct 06, 2004 10:57 am

If you ever notice, there is a little box on the overhead. That's what toggles the switch. When a trolley runs through it normally, the switch stays closed and the trolley goes straight. But when a trolley runs through the box with its turns signals on, then the switch opens and a the trolley goes in the desired direction. The tracklesses do the same thing.

If you've never created a model of something from scratch using materials you can find at the home and hardware stores, I'm afraid I can't do a lot in this forum to help you. You will need to design a trolley of some kind, find or design the electronics and motors assemblies to move it around, come up with a way of suspending the power lines and then make one of the designs for arms to reach up and grab the power. It's easy to find model trolleys but these run on model railway rails which actually provide the power. They have the trolley poles but just for show. Your internet searching skills are probably better than mine and maybe you'll find a kit - I didn't.

You may have to make one yourself. As a demonstration it doesn't need to be a beautiful period-accurate model of a trolley bus. Concentrate on the mechanisms and don't worry as much about what it looks like. Can you do the project with some friends? Maybe as a group the project will be a little less daunting.

Howard