Coupled Wheel Geometry (Fusion 360)

[Mark CParticipant @markc]

Murray, I can also confirm that when you are about a mile and a half from the gents (a wind sheltered wall would not cut it) and the only vehicle to get you back is a Scania prime mover with an air leak, getting the breaks off takes an eternity…. on the plus side, they do get a move on with not trailer!

Mark

[MuzzerParticipant @muzzer]

I'm guessing that you can probably EITHER do FEA on a rigid assembly (eg spring-mass) OR make a moving assembly (dynamic motion analysis). But unless I've missed something, I don't see how you can sensibly implement a blade spring in a dynamic assembly.

Unless you want to make a breathtaking animation, I can't see any benefit in trying to use CAD for this kind of design work. The FE analysis (resonance) would help to dimension the mass and spring elements but I suspect that beyond that you'd be better just modelling the parts as a static assembly.

Murray

[Mark CParticipant @markc]

Murray, That is what I was getting at. You could always do a full blown dynamic simulation but cost of equipment (not just the software) would be a serious investment and the skill would be past my pay grade I would think.

I take it then that fusion does not come with dynamic simulation?

Mark

[SillyOldDufferModerator @sillyoldduffer]

Thanks Murray and Mark. Good advice.

[Geoff TheasbyParticipant @geofftheasby]

John S, yes, I've seen this in truck racing. On one occasion it ripped off the rear axle which cartwheeled over the track with the propshaft flailing.

Geoff

[Neil WyattModerator @neilwyatt]

I once spoke to someone who had seen a coach propshaft come up vertically in the aisle…

Neil

[Owain SamuelParticipant @owainsamuel55325]

Posted by John Stevenson on 31/01/2017 20:11:09:

Idle thought.

How often does a full sized engine, or did . loose a coupling rod and what were the consequences ?

Thankfully not very often, the result is usually a spectacular derailment. It's happened once in preservation that I know of. There the little end pin became dislodged on a bullied Pacific running on the main line down south, the connecting rod dropped and very fortunately landed on top of the electrified third rail, so the crew managed to bring it to a stop. Net result was a major panic care of the ORR and RAIB (which considering I'm one of several fitters who sign these things off as fit to run on the main line for a large UK preserved railway lead to a bit of stress in my day job). Had the third rail not been there it had the potential to be a repeat of a identical accident in the 60's where a Britannia Pacific (similar sized engine) ended up on its side, with the train pilled up behind it.

As part of any main line fitness to run examination (FTR for short) I perform all the motion pins (usually secured with collars and taper pins) and all the crank pins with their caps securing the rods are examined for slackness, missing cotters, taper or split pins (delete as applicable), damage or signs of movement. Annually all the rods are stripped off and dye-pen NDT'd for signs of cracking along with the crank pins on all our locos (having just finished doing this on a BR standard 4MT 2-6-0).

Owain

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