bogie suspension problem

andrewnummelin
Posts: 374
Joined: Mon Jul 21, 2008 9:43 am

bogie suspension problem

Postby andrewnummelin » Sun Sep 19, 2021 6:42 pm

One of my current projects includes a couple of problem inside framed bogies so many common solutions will not work. My first thought went to compensation with moving side frames but I've become more attracted to sprung suspension. However, I've found problems with both.
The bogies have prominent cross stays (2" diameter) that essentially mean that the bogie sides are fixed relative to each other,
My second approach was to try the Masokits inside bearing sprung system but this is too large as shown below.
Capture.JPG

It may be possible to grind off a bit of the etch around the inner spring supports, but this would not work with the outer ends of the etch.

I can now only think of a couple of approaches:

- "CSB" - cut off the outer spring supports and use a single spring through both inner supports and just resting on top of the axel boxes with stops at the outer ends to prevent it sliding out;
- treat it like a compensated 0-4-0 loco with one fixed axel and a beam resting on the centre of the other.

If the latter approach is adopted, would it be better to have springs between bogies and body, or would 3 point suspension be better?

All of this is more complicated because the bogies have to pick up current and wiper pick-ups are not desirable!

Any comments or suggestions would be most appreciated.
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Regards,

Andrew Nummelin

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jim s-w
Posts: 2185
Joined: Wed Jul 30, 2008 5:56 pm

Re: bogie suspension problem

Postby jim s-w » Sun Sep 19, 2021 7:00 pm

You could actually assemble the brassmasters bogies with the outer frames backwards to give you inside frames if you needed too. Depends on what’s happening with the centre part of the bogie though. Just a thought
Jim Smith-Wright

http://www.p4newstreet.com

Over thinking often leads to under doing!

John Palmer
Posts: 825
Joined: Fri Jul 15, 2011 11:09 pm

Re: bogie suspension problem

Postby John Palmer » Sun Sep 19, 2021 11:42 pm

If current collection without resort to wipers is required then presumably you are planning for split axle collection?

I am currently contemplating a bogie design with split axles running in top hat bearings, from which current is conducted away to a power bus elsewhere on the locomotive. The plan is for the top hat bearings to be mounted in delrin bushes, so insulating them from the rest of the bogie. I envisage the delrin bushes being mounted in internal beams, to each of which some twist in the vertical plane can be imparted by mounting it on its own torsion bar. Each such torsion bar would be anchored to the external, cosmetic frame on the opposite side of the bogie, being first passed through the intervening opposite beam via a bore having sufficient clearance to permit some vertical displacement of that beam relative to the torsion bar. That's needed so that the internal beams have room to twist relative to each other. The idea behind having two torsion bars is to leave sufficient space between them for mounting whatever bogie pivot/secondary suspension arrangement is adopted, but a suspension that uses a single beam pivoting around a torsion bar may be feasible and a simpler solution. I have approached the design in this way because, like yours, the prototype of my bogie has prominent fixed cross stays, and a solution involving axleboxes sliding in horn ways will be obtrusively large due to the need to fit the bearing shells inside insulating bushes.

Hope my description gives some idea of my intentions, and that if nothing else the notion of a torsion bar suspension broadens your range of possible solutions.

I guess that with a 32mm wheebase bogie you are treating the need for some form of suspension for each wheel as obligatory. I've had no problems with rigidly mounted wheels in a 22mm wheelbase bogie, to which I've successfully applied a current collection arrangement that involves conductive bearing shells insulated from the rest of the bogie.

Philip Hall
Posts: 1943
Joined: Mon Aug 10, 2009 7:49 pm

Re: bogie suspension problem

Postby Philip Hall » Mon Sep 20, 2021 3:50 pm

This seems quite complicated. Given it’s a fairly short wheelbase bogie (8’0” is short, really) if you use absolutely concentric wheels it will run very reliably without any wobble if you build it rigid. Or with a little twist by using thin end beams. A touch of play in the bearings will also help.

I guess I’m being a bit heretical here if you want to follow the true path of engineering niceties, but it would be a practical solution.

I must emphasise that the wheels have got to be spot on for this to work reliably.

Philip


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