Trolley wheel arrangment

[Half centreParticipant @halfcentre]

Which is better?

[Half centreParticipant @halfcentre]

I am going to build a slightly elongated drive trolley, long enough for myself and a couple of passengers (grandchildren!). First thoughts were to build a couple of sprung 4 wheeled bogies and have one at the front, the other at the rear – a conventional arrangement. I then wondered about making 4 x 2 wheeled sprung 'bogies' and distributing them along the length of the trolley. The 2 sketches show the alternatives, the X marks the centres of rotation. I would appreciate any opinions as to the advantages and disadvantages of the 2 designs. I have never seen the distributed arrangement so presumably it has significant problems?

Martin

[JasonBModerator @jasonb]

Try drawing an arc through the 4 axles on the right and you will never get it to fit, that is why waggons and coaches have them like on the left

[Mike PooleParticipant @mikepoole82104]

I would think the two wheel arrangement would just turn and lose contact with the rails, the four wheel unit cannot turn between the rails so must follow the track.

Mike

[Tim StevensParticipant @timstevens64731]

Your four single axles should be OK unless you need to go round any bends. the two comments above should explain why.

Tim

[Half centreParticipant @halfcentre]

Thank you chaps – makes perfect sense!

Martin

[Perko7Participant @perko7]

A lot of 19th century railway rolling stock having 3 or 4 axles used a single pivoting axle at each end which was linked to the centre axles using a mechanism that caused the centre axles to move sideways to match the track curvature when the end axles pivoted. They were generically called 'radial-wheeled' and there were several designs, Adams, Cleminson and Clark being three that i know of.

I've not seen anyone try to model any of these as an operating system on a miniature railway, although I've seen a few pictures of working models on O-scale period rolling stock. Could be an interesting challenge if someone was interested (or crazy) enough .

[Neil WyattModerator @neilwyatt]

Within reason, you can simply leave the flanges off the centre wheels – it all depends on what radius of turn you need it to cope with.

[roy entwistleParticipant @royentwistle24699]

Neil Not if they pivot you can't

Roy

[Half centreParticipant @halfcentre]

Very interesting – thank you all. I was wondering why the Victorians thought it was worthwhile? It does sound rather complex and costly?

Martin

[Perko7Participant @perko7]

Most of the radial axle designs were intended to reduce frictional resistance on curves as, at least theoretically, the axles would always be aligned radially to the centre of the curve (hence the generic name) making the most efficient contact between wheels and rails.

In normal 4-wheel wagons, and even in bogie wagons, the axles are not radially aligned to the track curve, so there is some sliding contact between the root of the flange and the inside edge of the rail head.

In practice these radial systems didn't work quite as well as hoped due to frictional resistance to the rotating and/or sliding of the axle housings in the wagon chassis.

Queensland Railways also had quite a lot of 4-wheel rolling stock having Grovers bogies, with the two axles each held in pivoting frames which were connected by crossed rods. The theory was that the axle frames would rotate to follow a radial position induced by track curvature. Again, success in practice did not always follow the theory.

[Tim StevensParticipant @timstevens64731]

The idea of radial axles is sound, but there is another effect which complicates the issue – the fact that both driven wheels rotate at the same rpm, even though the outer one on a curve has further to go. As a result, the axle tries to go straight on at all times, regardless of any guidance system.

Or do your loco drivers depend on the trick used with Fraser Nash cars (which also had no differential gear)? They seem to rely on heavy-footed owners causing both driven wheels to spin on corners, so the axle is not constrained by side loads. Older owners of such cars tended to be very skilled – a consequence of the Darwin effect, no doubt.

Regards, Tim

PS was there ever a locomotive with a differential?

Edited By Tim Stevens on 14/04/2018 14:56:57

[Neil WyattModerator @neilwyatt]

Posted by Tim Stevens on 14/04/2018 14:56:18:

PS was there ever a locomotive with a differential?

Edited By Tim Stevens on 14/04/2018 14:56:57

No, but one or two with coned wheels

Neil

[John BaguleyParticipant @johnbaguley78655]

If you want a really free running design for a driving truck or passenger car then look at the design by David Hudson that has self steering axles. He described the theory and construction in ME for 2003. His is by far the best design I've come across and used. Our club driving trucks and passenger cars are to his design and they are very free running.

Our club went to the Burton track some years ago and one of our members took his Hudson design driving truck. At the end of the day, we decided to see just how far it would go on it's own. It was given a good push and did a complete circuit of the Burton raised track and would have carried on if we hadn't stopped it!

I believe that Dave Noble still offers complete kits for the driving trucks as well as individual components.

I'm just about to convert my normal 4 wheel fixed axle truck to the Hudson design as at the moment it has too much drag for small 2½" gauge locos to pull around easily.

John

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[SillyOldDufferModerator @sillyoldduffer]

Posted by Half centre on 13/04/2018 18:04:04:

Very interesting – thank you all. I was wondering why the Victorians thought it was worthwhile? It does sound rather complex and costly?

Martin

Could it be because the Victorians didn't have easy access to the materials needed to make long wheel base vehicles?

Before Bessemer's converter steel was a high-value specialist product, produced in small quantities and too expensive to be widely used in construction. Cast Iron is too brittle and weak in tension to be good for framing a vehicle. Wrought Iron would be considerably better for the purpose than cast iron, but it too is expensive to make, and it has a fibrous structure making it awkward for many purposes. Ordinary iron is quite soft. My guess is that early railway rolling stock was limited because it was built from wood and iron. A long carriage needed a pair of central wheels to take the weight.

Bessemer mild steel took about 10 years to debug and catch on. Add to that British Industry's famous reluctance to modernise and it's no surprise that the first British bogie carriage didn't appear until 1874; I wonder if it had a mild steel frame, a much better material for making a long span frame? I bet someone on the forum knows!

Dave

[Jeff DaymanParticipant @jeffdayman43397]

Lots or Victorian wrought iron structures hundred of feet long – think bridges. Don't think material was the main issue why bogies/trucks and long rail vehicles were not implemented sooner.

I believe bogies/trucks had widespread implementation in the USA before they became common in the UK. Most American 4-4-0's in the 19th century used them to deal with rough, quickly laid track.

It may be that because it was viewed as "American" technology it would be viewed as "following American practice" by the lead engineers in the UK at the time, who liked to do things the British way / be the leaders in technology.

It doesn't matter what the reasons were in 19th century, bogies / trucks are prevalent on rail vehicles around the world today because they work and are simple to make and service. Why re-invent the wheel ? (or in this case why reinvent wheels axles sideframes bolsters etc?)

[Half centreParticipant @halfcentre]

Interesting thought about the availability and cost of materials. It was the idea of spreading the load and stopping 'flange drag' the which sparked (my not particularly well thought through!) musings. It is also interesting to ponder how often ideas were implemented (or not) for less than fully logical reasons! Thank you for the ME lead – so off to the club library later in the week.

Martin

[Nick HulmeParticipant @nickhulme30114]

For a solid steering axle your point of rotation should be in front of the axle centre line, this gives your steering a degree of self-centre, it's more exciting if you have the pivot on the centre line though

[Nick Clarke 3Participant @nickclarke3]

Posted by Tim Stevens on 14/04/2018 14:56:18:

PS was there ever a locomotive with a differential?

While not a differential in the sense that a road vehicle has one, the Fell Diesel Mechanical locomotive BR 10100 certainly used a differential arrangement to couple its engines together.

https://en.wikipedia.org/wiki/British_Rail_10100

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