Adding Weight

[JonL]

I've found with the Britannia i've got plenty of oomph but the adhesion isn't great. I'm thinking of adding weight in a few places, probably in the form of lead melted into pockets to suit the spaces. Anyone got any better ideas? Any tips please?

[dhamblin]

Under the cab footplate and between the frames. That's my plan over the Winter...!

Are you thinking of stiffening the springs to compensate for it sitting lower?

Regards,

Dan

[JonL]

Dan,

I hadn't considered the spring rate, but I also don't want to go to a big strip either. I think if needs be I may adjust the preload on the springs but probably won't change them out at this stage.

When I made her I reinforced the cab floor with some box section which the whistle hangs from, that seems like a good place to stow some. At the moment when traction is low I press on the footplate floor and it soon grips again.

It's either that or I buy some tungsten! When I was an apprentice we had rivetting blocks of depleted uranium. I don't fancy playing with those anymore.

[uuu]

You could wind some lead strip round an axle without affecting any springing.

Wilf

[nonort]

Can I humbly suggest that if pressing down on the cab floor makes that much difference then the trailing truck is carrying 'weigh' to much weight. Before adding lead to an already fairly heavy engine check out the weight diagram of the engine. I can't remember the figures now but if you can, check out 2000 IMLEC at Leyland results. The had a weighbridge to check the axle loads of the Southampton Clubs 'Brit'. I know that filling the boiler to the running level made a sizable difference to the balance of the engine. I vaguely remember the rear truck only having about two pounds on it and about four pounds on the bogie axles. I did fit side control springs to the bogie to make the engine steer better. One last check make sure the tender is not lifting the rear of the engine through the drawbar,
Best of Luck.

[jo479]

winding lead round the axle seems a good idea, never thought of that, thank you

[dhamblin]

Make sure you lock it to the axle though otherwise it could move across and rub on the bearing.

Funny enough we looked up the price of a cube of tungsten at work the other week - eye watering! Will have to stick with lead for now.

Regards,

Dan

[kipford]

Whilst adding mass to axles is the most effective solution to aiding traction, I would not be very happy with pieces of lead strapped to the axles whirling around underneath the loco. it is a very poor engineering solution fraught with problems and is a potential safety hazard. As Dan says it needs to be well attached, but there are also potential issues with out of balance forces and the fact the lead will probably start to creep under the constant centripetal load from the rotation of the axle unless it is completely encased.
Just my opinion
Dave

[JonL]

It's a really good discussion, thank you all. It's leading me down a path I didn't anticipate going down with axle loadings etc. I wanted to avoid setting up each axle in turn but it may be my best best.

I'm sure a leaded axle solutions is workable. even if it isn't winding it on.

[oldnorton]

I have watched a heavily loaded big engine (+50kg tungsten) slip just like all the others when the track is wet and oily.

The most important feature is for all the axles to be freely moving up and down and for the loading on each to be about right.

Norm

[coniston]

You may want to have a look at this thread of mine from a few years ago where I balance the axle loadings on my B1 to Martin Evans Springbok design.

modeleng.proboards.com/thread/14222/axle-weighing-first-experiments

Chris

[dhamblin]

Out of interest Chris have you managed to road test the B1 yet and how do you feel it performed given the adjustments you made?

From that thread there is another interesting variable thrown into the mix - wheel material. Given most wheels are cast iron you could get greater adhesion through the friction coefficient just by fitting steel tyres.

Going back to the original question Jon, I reckon there is also room to add a bit within the frame stays on a 3 1/2" Britannia, assuming you've got the machined castings rather than machined from solid block ones. There is also space under the running boards if the mass needs to be evenly distributed across the drivers and a nice void within the smokebox saddle under the blastpipe. In terms of the balance you could also look at how long the brackets are that bear the rollers on the trailing truck frame, because that must have a significant impact on load the rear driving wheels see.

Regards,

Dan

[oldnorton]

Do steel tyres grip better than cast iron? I also thought that they might, but recent evidence suggests not to me.

My Britannia has made several visits to Gilling East where there is a notorious section on the down line climbing to the station past the village hall, just before and then after the level crossing. When it is damp early morning, and much worsened on the second or third days when there are traces of oil, all engines are at the limit of adhesion. This year I had newly fitted steel tyres (EN16 steel equivalent), with all the springing arrangements being identical to the previous year on cast iron wheels, and when hauling 13 Mk1 coaches I still slipped.

The track changes from aluminium to steel at the road crossing and back to aluminium again. Yes, you could detect and use the slight additional grip on the steel rail section, but it is only a small improvement. That same regulator setting could then be held as you move back onto the aluminium track with no additional slipping because the train's momentum has picked up.

None of this slipping occurs without the heavy train weight of course. My Britannia has quite soft springing (compliant) and its standard 100kg is evenly spread over all the wheels.

Norm

[coniston]

Hi Dan, yes the B1 has more traction than before. I did a number of test runs on our track at Fareham in preparation for IMLEC last year and was able to add a further two adult passengers without slipping to a halt at our most difficult part of our track. The IMLEC run was successful as far as I ran for the 1/2 hour with only minor slipping on wet rails on 2nd day of competition so I believe it was worth the effort.

I have a couple more things I want to do and one of them is fitting steel tyres although from Norms experience I need to have a think about it. I believe the steel tyres are a benefit on steel rail but maybe not so much if at all on aluminium. Also I had a long chat with a very experienced IMLEC competitor who said none of his locos has steel tyres only standard cast iron wheels including his winning locos so maybe it's not such an improvement?

Sorry Jon for hijacking your thread.

Chris

[johan]

Sept 18, 2024 18:22:55 GMT coniston said:

I have a couple more things I want to do and one of them is fitting steel tyres although from Norms experience I need to have a think about it. I believe the steel tyres are a benefit on steel rail but maybe not so much if at all on aluminium. Also I had a long chat with a very experienced IMLEC competitor who said none of his locos has steel tyres only standard cast iron wheels including his winning locos so maybe it's not such an improvement?

Sorry Jon for hijacking your thread.

Chris

Efficiency is a game of diminishing returns. The first big steps are "easy" but then it becomes a game of a tiny bit here and a tiny bit there. I believe steel tires have an advantage. Just like a good weight distribution, a good suspension arrangement to get that weight on the rails etc. As long as you haven't got all the big shortcomings solved, solving a less important one will not be noticeable immediately. But it will be there.

Even how high above the rail you connect your train (in relation to your axle height above the rail) is going to make a difference in the end.