Hi,
I am presently laying out a 6' by 11' full size round the room track plan copied from my previously drawn scaled paper plan. I intend using easements and have Armstrong's book so I have learnt how to lay one out.
However, I recently purchased a four foot Asymmetric Drawing Bow that can be held in position using an attached strap (from Lee Valley in Canada). Has anyone tried drawing curves in this way and I guess the bigger question is, will an asymmetrical curve act as an easement? I don't want to use the bow, lay out the track and find I messed up.
Any thoughts or help would be very much appreciated.
Many thanks,
Roger
Thanks for the responses I have attached the link to the Lee Valley site, which I hope opens ok.
The bow is used for woodworking but when I saw it I thought it would be perfect for easements. I had another look at it just now and the thicker end starts off in a straight line and gradually curves (like a French curve I think) much like an easement. The other end comes in a little too much for my minimum radius but I'll just revise that part slightly.
The thing I like is that the nylon strap can be adjusted and that way the curve is held in position and I can make small adjustments as necessary. The advert (link) will show you what I mean.
http://www.leevalley.com/wood/page.aspx?c=1&cat=1,42936,50298,44631&p=44631
When you paste the link, hit the "Enter" key afterwards and it will activate the link like this.
Also, I don't see why it coulsn't be used. Looks like it would give a nice smooth easement.
cp7400 wrote:I intend using easements and have Armstrong's book so I have learnt how to lay one out.However, I recently purchased a four foot Asymmetric Drawing Bow that can be held in position using an attached strap (from Lee Valley in Canada). Has anyone tried drawing curves in this way and I guess the bigger question is, will an asymmetrical curve act as an easement?
However, I recently purchased a four foot Asymmetric Drawing Bow that can be held in position using an attached strap (from Lee Valley in Canada). Has anyone tried drawing curves in this way and I guess the bigger question is, will an asymmetrical curve act as an easement?
Easements are another thing that I believe people over think. It is simply a matter of starting the curve a little bit more gradually and tighten it to the fixed radius. Flex track will make its own "easement" if it is laid from the fixed curve outward to the straight.
Andy Sperandeo wrote an article in the November 2006 Model Railroader described about 2/3 down the thread, describing the "bent stick" technique which you are using...
http://www.trains.com/trccs/forums/902263/ShowPost.aspx
Andy's comment: Whether these curves are mathematically "accurate" or not doesn't matter at all to me. They work, which means they provide improved appearance and smoother operation by minimizing the offset between cars entering and leaving the curve.
I have a plastic 8-foot "Trimboard Divider" (slotted on each side for wall paneling) and another cut into 4-foot sections available at Lowes-type stores for under $2.00 each that work nicely as a bent stick for easements, or to sight-up larger flowing flextrack radius curves.
Conemaugh Road & Traction circa 1956
This afternoon I drew an easement offset by about 1/4" from the tangent to the circle. as per Armstrong. Then I tried out the Asymmetric bow and lined up the bottom (thicker part) of the bow in line with the straight part where the tangent just starts to 'ease' in and towards the circle. The apex of the bow was bent until it lined up with the top on the circle. So that meant I had both the bottom and top of the bow matching the originating and final parts of my easement. (I hope that makes sense).
Interestingly enough the bow gave a much more pleasing transition from the tangent into and through the circle. The only real difference was that the bow produced a slightly more elongated curve.
I read that part from Andy Sperandeo just now and I realise the simple bending of a stick achieves the easement effect. Having tried the Asymmetric bow I find, as I mentioned before, it easier to adjust the strap which gives me better control and all one handed!! I also now like the way the bow gradually curves. In addition I can repeat the easement if desired or just flip it and with some small adjusting continue my curve.
CP: I thought of the same thing when I saw the Lee Valley folder. Thank you for trying it our for us.
What sort of lengths and radii does it look capable of?
--David
Hi BR,
In response to your question I managed a very graceful 19 inch easement. The bow is 48 inches from tip to tip and I found the first 4 inches or so, at the thicker end, gave me a straight line that then led into the start of the easement.
I also wanted a 15 inch curve at the bottom end of my layout with two straights leading into each of the arcs (one to be hidden). The bow gave me a good initial easement and then I flipped it and lined up for the other side.
All in all well worth the money. The other bow looks useful too.
Hope this was some help.
Regards,
An electrical conduit fish wire can be used to form a curve and will automatically form your easements on both ends.
The technique I use is to fasten the end of the fish wire with T-pins at one end of the desired curve and then play out enough of the fish to reach the other end of the curve, with its center in the desired location. I then pin down the second end and trace the arc thus formed.