minimum radius for helix

In message , Chris Wilson writes

Oi! cheeky! The playing field is the other side of the fence from the back garden!

Helpful hint: move away from Biggin Hill!

Fairy nuff.

Reply to
John Sullivan
Loading thread data ...

"Chris Wilson" <

I've been in North America, where all grades are expressed as a percentage, and I still convert them to "One in Somethings" as it's easier to envisage.

More complex is the North American method of expressing (Prototype) railway curves in degrees of curvature, a "six degree curve"? Wassat then?

-- Cheers Roger T.

Home of the Great Eastern Railway

formatting link

Reply to
Roger T.

"Boards"? People in the UK still build model railways on "boards"? :-)

Yes, just making mock but seriously, do people still build their model railways on a flat board?

The only place you'll find a "flat board" is under one of my yards. Even then, the "flat board", 3/4" Good One Side plywood was cut so that the outside edges flowed with the planned shape of the yard.

-- Cheers Roger T.

Home of the Great Eastern Railway

formatting link

Reply to
Roger T.

Exactly. I have been reconstructing our layout, but I'm still restricted to an 8' by 4' area and the run around track is a must. I have been testing the track as I lay it with a pair of Bachmann intermodal bogie wagons. It doesn't take much of an imperfection to get these to jump the rails.

Mark Thornton

Reply to
Mark Thornton

The problem with percentages is that right where the gradient becomes more and more critical the percentage change becomes smaller and smaller.

(a bit like Litres per 100 Km for petrol consumption)

Regards, Greg.P.

Reply to
Gregory Procter

I'm not sure what you mean by that. I always found l/100km to be a very useful measure of fuel efficiency, especially when we encountered signs like "No food, water or petrol for the next 300km". Of course buying petrol in litres and measuring distance in miles as in the UK is just plain stupid.

Mark Thornton

Reply to
Mark Thornton

"Gregory Procter"

In North America, grades were designed as percentages right from the start, therefore, you don't get odd ball percentages. .5%, 1%, 2%, grades are common, whereas the equivalent of UK grades such as 1:233, or 1:4351 for example are almost unknown.

North American grades are usually expressed in round numbers.

It's like our mileage posts, attached to the nearest convenient telegraph pole, when they had them, now replaced by the stump of the telegraph pole and still not accurate but "close enough".

-- Cheers Roger T.

Home of the Great Eastern Railway

formatting link

Reply to
Roger T.

That being the case we can give thanks that this is a group that is concerned with UK outline :-)

Reply to
Chris Wilson

I trust you are kidding??? The gradient is caused by the track having to climb between two points with the track taking whatever course the budget allows for. Every gradient is going to be an odd-ball percentage.

There's the big clue! 1:99 and 1:101 are both likely to be labelled 1% in the US.

Ahhh, so they are actually "x multiple telegraph posts".

I like talking to you, you introduce more arguments per posting than Martin and yet there's never a hint of name calling between us! ;-)

Regards, Greg.P.

Reply to
Gregory Procter

What I'm getting at is that the difference in numbers between a thirsty car and a very thirsty car appear minimal - eg 7.5L per 100 km and 7.9L per 100 km is 5% difference. In mpg (or km/L) you can round to whole numbers (as many of us do) and still get a significant number.

That's a tough point to argue against!

Reply to
Gregory Procter

"Gregory Procter"

More than likely. However, engineers would still probably make it a 1% grade due to the: - "That's the way we do things over here."

I'm sure odd ball grades like 1.247% must exist, like the UK has odd ball grades such as 1:1352 but I can't off hand recall any ever being mentioned. I really believe that engineers build the railways with "round" grades. .5%, 1%, 1.25%, 1.5% etc., etc.

Bug off. :-)

-- Cheers Roger T.

Home of the Great Eastern Railway

formatting link

Reply to
Roger T.

Phil: Well, I suppose that to allow direct correlation to the effective loss of power / additional effort reuired, we should all quote the inclines expressed as the SINE of the Incline angle .... instead of the TAN

Reply to
Phil

Like the prototype, we want our tracks to rise a specific distance (o) in whatever length (h) we can provide - that ratio is practical and makes sense to me. I don't carry any gear with me to measure the incline angle but I do have a tape measure handy.

Regards, Greg.P.

Reply to
Gregory Procter

If you're going to build a decent helix then build it properly on a rigid base! That would be a flat base with solid framing so that it will not bend or flex.

Reply to
Gregory Procter

From : "Degree of Curvature" - Sharpness of a curve measured by the number of degrees of turn in a unit distance, usually degrees per 100 scale feet.

Reply to
Bruce Fletcher

Gregory Procter wrote: [...]

The helix track base is supported by posts (on the inside, usually), which are supported by the layout substructure. That's rigid enough, and then some.

It's a question of cost, convenenience, and available skills. For large layouts, flat table tops are an unnecessary waste of good lumber. For very small layouts on the order of a couple feet square, such as the micro-layouts built by some NG freaks, er, sorry, modellers :-), a corresponding chunk of 3/4" or even 1/2" plywood may be rigid enough as is. Hollow core doors are very light and rigid, and have been used successfully as bases for smallish layouts.

See Linn Westcott's book on building benchwork, which introduced the "L-girder" method. He found (as bridge engineers discovered before him) that it's not the amount of material but its shape that determines rigidity and strength.

HTH&HF

Reply to
Wolf Kirchmeir

And done that way to simplify surveying. You can't lay out a curve - you have to lay out a series of chords. NB that even if you specify a curve by radius (as the Brits and Europeans do), you still have to know the angle through which to turn the transit as you lay out the stations marking the centre line of the track. That involves calculation, or look-up tables.

With "degree of curve", you already know - the calculation to determine degree of curve was done when the line was laid out in the drafting room. All you have to do is set up the transit on the last station, sight back to the previous station, tumble (reverse) the scope, and rotate the transit X degrees right or left to determine the direction of the next chord in the curve. Below about 5 degrees of curve, the error of rotating an additonal X degrees to mark the next two or three stations is equal to or less than the measuring error, so you in practice set up every three or four stations. Quick and dirty, maybe, but easy and cheap. :-)

There's a good deal of unnecesary precision in European practice, I suspect the German influence. :-)

Reply to
Wolf Kirchmeir

"Gregory Procter"

All the N.A. articles I've read have the inside of the helix open for access, I've yet to read about one with a "solid" base. Mind you, all the ones I've read about have a radius of something like 30 plus inches or more to achieve a minimum 2%, or 1 in 50, grade on the helix itself, so there is more than enough room to stand inside the helix structure.

-- Cheers Roger T.

Home of the Great Eastern Railway

formatting link

Reply to
Roger T.

"Bruce Fletcher" <

As I wrote above, "Wassat then?" :-)

-- Cheers Roger T.

Home of the Great Eastern Railway

formatting link

Reply to
Roger T.

In message , Gregory Procter writes

Dear Greg

Where can I get a flat base that's 16 feet x 8 feet?

Reply to
John Sullivan

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.