First Scratchbuilding Challenge - Chassis queries

[LynxModeller]

Hello all,

I have been reading rmWeb for a number of years and have built a couple of very simple kits in that time, but having decided to have have a go at scratchbuilding, I decided to rejoin and post, both to share what I was doing and also to seek advice.

 

I am starting a new layout from scratch, no existing rolling stock and therefore I have decided to build a small coach and locomotive as a demo to see how I get on.  I am waiting on the lasercut coach parts coming back, so  I am currently designing the chassis in CAD (Fusion360) and will think more about the body, once I have successfully built a powered chassis that runs without problems!  This is 5.5mm scale, three-foot gauge design, based on a Kerr Stuart locomotive provided to the Lough Swilly Railway in Ireland - although the layout will be Wales based if I proceed.

 

5.5mm in 3ft gauge, uses 16.5mm trackwork, but in terms of size, sits part way between OO and O gauge.  So my first question (and I appreciate there is probably no single right answer) to those of you who have built chassis from scratch before, how should it be sprung?  I am thinking that a compensated chassis, with sprung horn blocks is the way to go.  Given its is a shunting loco, smooth operation will be key.  I have not built a compensated chassis before, but have just acquired the Flexichas book by Mike Sharman from Amazon for reference.  But any thoughts/views/suggestions/pitfalls to avoid would be welcome.

 

I will be using Markits wheels/axles/cranks - the model is an outside frame design, and my plan is to pair it with a High Level Kits Loadhauler 80:1 gearbox and 1426 Motor (possibly with a flywheel), driving on either the front or rear axle of the six driving wheels.  Is there any benefit to driving more than one axle from the single motor?  Again, my thought is to include pick-ups on all wheels if possible.

 

Thanks in advance.

Richie

Edited June 19, 2020 by LynxModeller

[andrewnummelin]

You mention springing and compensation so I think there is only one way to go and that is to use HighLevel's hornblocks and continuous springy beam set up. http://www.highlevelkits.co.uk/jigpage.html

 

[brossard]

I've built one or two chassis from scratch.  I also tried CSB on a chassis but found it a terrible faff.  The gearbox must be narrow enough to fit between the hornblocks (there are reduced thickness hornblocks for the driven axle).  In your scale this might not matter but it is crucial for 00.

 

I have always found beam compensation to be the simplest method, starting from my very first chassis kit.

 

I made this for a Deeley flatiron 0-6-4T:

 

 

 

High Level hornblocks are excellent.  Plastic sandboxes drilled and pinned.

 

 

 

You can see the pivot and beam in this view.

 

I never did finish it, I sold it on when I switched to 0, hopefully the buyer will complete the job.

 

John

 

[LynxModeller]

2 hours ago, brossard said:

I have always found beam compensation to be the simplest method, starting from my very first chassis kit.

 

Hi John,

Thank you for the response.  I need to have a bit of a read up, but what is the difference between CSB and beam compensation?

 

@andrewnummelin I'll have a look at the HLK hornblocks. Hadn't realised they did them.

 

Richie

[brossard]

CSB = Continuous Spring Beam, some reading for you:

 

http://www.clag.org.uk/beam-annex3.html

 

For beam comp. you need to put two axles in hornblocks and put a beam on top.  This beam can rock from axle to axle, so needs a pivot, and the hornblocks on each axle can rock side to side, bearing on the beam.  This allows the wheels to follow the track and will "compensate" for slight unevenness giving better electrical pickup and improved tractive effort.  The pics above should illustrate this.

 

The first pic shows HL hornblocks.

 

John

 

 

Edited June 20, 2020 by brossard

[LynxModeller]

6 hours ago, brossard said:

CSB = Continuous Spring Beam, some reading for you:

http://www.clag.org.uk/beam-annex3.html

 

Thanks John,

That article is wonderful, very interesting and informative to read - thanks for sharing.

 

Richie

[andrewnummelin]

I should have added the point that John mentioned regarding space between frames in OO sometimes being a restriction, however I'd assumed that as your model is to have outside frames you would put the bearings in those, so leaving room for any gearbox.