Tips for a DIY Model Railroad Trammel
Gerry LeoneDescription
A useful tool to have in your arsenal of model railroad train supplies is a trammel. Essentially, a trammel is a large compass that will help you accurately draft curves before placing the sub-roadbed and laying flextrack. Building your very own trammel is cheap, easy, and requires few materials. This tool will assist you in planning your track layouts by providing a consistent arc every time.
Constructing a Trammel and Putting it to Use
Laying curved model railway track can be tricky. It takes a bit of planning and sketching before placing the sub-roadbed and laying the track. During this process, you can use a trammel to draw the curves. This method doesn’t require any estimating or guessing. With the trammel you will draft the exact radius curve needed for your track. In this particular video, NMRA Master Model Railroader Gerry Leone demonstrates how to create a homemade trammel to help you create 30-degree radius curves. Tracks are sold in various radii, but the trammel can adjust to any size needed.
Gerry demonstrates not only how to make a trammel, but also how to properly use it. Modeling trains often means working in tight areas around the layout. Gerry developed a trick for using the trammel when you lack a location to plant the focal point of the tool. It serves as a great technique for working in corner areas that are not obstructed.
Making a trammel will prove to be useful when creating curved model railway track. It is simple to create one just like Gerry’s. Follow along for the steps of creating and using the tool. With these tips and tricks, you will create a perfect arc every time.
The first tool I'm gonna show you that'll help you get from paper to plywood is something called a trammel. A trammel is basically nothing more than a giant compass that'll help you draw curves very, very, very accurately. Except in this case, instead of a compass, it's a yardstick. You can use a yardstick. You can just tape a pen or pencil on one end, you can take a screw or a nail on the other end, and use that to draw your curves. I happen to have a commercial set here that I bought from Micro-Mark. It's very nice because it lets you very quickly and easily move your pencil or your focal point on the yardstick with a screw here, it's also got a very nice pencil or pen holder. The other side also has that same sort of adjustment and a real nice point on it. In my case, I'm using a 30 inch radius curve on my railroad, so what I want to do is I want to set the pencil here at the one inch mark, and the reason that I'm setting it at the one inch mark is it gives me a lot more surface area for the pencil holder to grip to. And again, because it's a 30 inch radius, I'm gonna set the other end, the pointed end, at 31 inches. So now I've got 30 inches between my pencil and my point. And what you do is if you're cutting your sub-roadbed out of plywood or some other material, and you're gonna use your trammell to draw your curves, it's easy enough to just plant your point and draw that curve, again, like a giant compass. And you get a very, very accurate curve that way. There's no guesstimating or estimating on getting that exact 30 inch radius curve. Now, in my case, as you can see, we're going to be putting a line for my track center line on the upper deck of my layout, and there's no real place to put the point of the trammell. So what do you do in this case? Well, in this case, I'm going to use a camera tripod. This is an inexpensive tripod, you can pick them up for actually just a few bucks, and use it for nothing more than a trammel focal point here. My particular tripod has some screws in the head of it, which makes it very convenient to be able to plop that point right down into the head of one of the screws and know that I'm always going to be using exactly the right, the same point every time I draw this curve up here. So what I want to do is start to draw that curve, and it's very important that when you're going to join two pieces of straight track that you know exactly where those straight tracks are. In my case, I've got a piece of flex track here on the upper deck, a piece of flex track here, I know that's where my straights are going to be, and I want to just join these two pieces of straight track with a 90 degree curve. So what I'm going to do is remember which screw I'm putting my trammel point in, and then just adjust the position of the tripod so that I get the pencil on my trammel in about the center point of my flex track. That one looks pretty good. We'll move it over here, and I've gotta move this toward the track about an inch or so. So we'll do that. We'll go back and check this. That's very good. And when you're ready to draw, again, remember what screw you're in, I get my flex track out of the way here, and I will draw a curve. And what I'm going to do is draw a curve that's a little bit greater than 90 degrees, because that'll give me a nice arc that I can line that tangent track up with when I'm ready to draw where the straight tracks go. So I'll put it in my screw, I will draw my my curve, and try to make sure that you don't bump the tripod or move the tripod as you're doing it. So we'll draw a nice curve here. If you can find a pencil with like a number three lead in it, which is a very soft lead, that'll give you a nice dark mark. You can also use, again, a magic marker to draw your line, and I'm going well beyond 90 degrees here. And that's my curve. That's a perfectly aligned 30 inch radius center line for my cork roadbed that I'll be laying down later on. Now, this works great, as I said, if you're cutting your sub-roadbed out of plywood, you can move your pencil in and out to draw the cut marks and still have your center line in the middle of that piece of plywood. Now, it works great in a situation like this where it's unobstructed, but what happens if you have an outside curve, and what happens if that outside curve has a backdrop on it already, or some other obstructions? We'll take a look at a tool that'll help you draw perfectly aligned 30 inch radius curves, or whatever your radius happens to be, on an outside curve.
I used something similar using 2 pieces of thin wood. the outer 2 were clamped to the benchwork and the center one ( a yardstick) used for the radius. I also drew my curves 1/4 to 1/2 inch inside the tangent track to allow for easement transition.
Trammel should be parallel to the plane of the roadbed to get the true radius desired. In the video, the trammel appears to be angled downward from the pivot point and not parallel to the roadbed.