Tender CSBs and motor torque

davebradwell
Posts: 1174
Joined: Fri Jan 18, 2019 3:48 pm

Re: Tender CSBs and motor torque

Postby davebradwell » Fri Jan 29, 2021 9:48 am

Re sideplay in tender axles, you'll find that even with none there's enough clearance between wheel and rail to get it round any curve you might encounter - down to 3ft with specified gauge widening of course. In practice there's a bit of running clearance in the bearings which gives a little more movement. Doesn't WillL have a facility for checking this? 0.3 brass is about scale for the frames and BR and lMS tenders had very narrow frames so you might use Markits brgs to get them as close as poss. Spring plates can go round flange of brg. Take care to hold the springs close to the frames to avoid shorts which can be a problem if there's sideplay.

I want to be clear that I believe your Dave Franks chassis will work perfectly well and have just remembered a couple of inside framed tender chassis I've etched for friends which carry the motor and work well at mainline speeds behind B17 and B12 hauling long trains. My A1 was just an extreme case to illustrate that the obsession with leaning is a distraction. You could, of course, just dig slots in the back of the Bachmann axleboxes and adjust the width.

Branchlines sell a useful drive shaft with 2 u/js and I'm betting a roadrunner+ will fit. It just needs a simple vertical tab to restrain it. 33:1 and a Zimo decoder for control - perfect.

DaveB

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Will L
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Joined: Sun Jul 20, 2008 3:54 pm

Re: Tender CSBs and motor torque

Postby Will L » Fri Jan 29, 2021 12:45 pm

davebradwell wrote:Re sideplay in tender axles, you'll find that even with none there's enough clearance between wheel and rail to get it round any curve you might encounter - down to 3ft with specified gauge widening of course. In practice there's a bit of running clearance in the bearings which gives a little more movement. Doesn't WillL have a facility for checking this? ...


Yes see this thread Track Gauge Widening, All You’ll Ever Need to Know. The first page contains a series of graphs which should answer the question for most wheelbases and a copy of the spread sheet that does the maths.

Since I came across the 2mm tube axle running on a 1mm pinpoint axle idea that's the way I would go for six wheel centre axles. Often not necessary for short wheelbase tenders but you have to do something on a 6 wheel coachs.

bobwallison
Posts: 131
Joined: Mon Jul 12, 2010 9:42 pm

Re: Tender CSBs and motor torque

Postby bobwallison » Sat Jan 30, 2021 3:11 pm

Dave,
Thanks for the additional input and reassurance. Lanarkshire's tender chassis duly ordered.

As for the thread on sideplay - wow and double wow! I hadn't realised there was so much to say about it. I think I'll just stick to Pythagoras.

Bob


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