Monday, March 14, 2016

Another Method for making a ‘Chuff Cam’

Sometime ago I did a post on how I make ‘chuff cams’ for model steam locomotives using Super Glue (ACC).
Erik Bennett sent me an email recently with his method so I asked him if he minded if I posted on the blog. As a result with Erik’s agreement here is his method for setting up a ‘chuff cam’ on a model steam locomotive.

Hi Ray,
I’ve put chuff cams in a number of locos, previously using a piece of 35mm film negative, cut to shape and superglued to the back of the wheel.

I saw your blog a few months ago where you described the technique of painting superglue on the back of the wheel.

Knowing how hard superglue is when it sets, I thought it a great technique and decided to try it on my next loco.
Well, I just finished a loco and it works great.

So, thank you for posting your superglue technique.

For info, I modified your method slightly and offer it here as an additional method:

I found it a bit tricky to get a clean edge when free-painting using the pencil mark method.

So I cleaned the superglue off my early attempts and cut 4 identical strips of adhesive tape.

The strips were about 3/4 the radius of the wheel in length and wide enough so that four strips gave four equal make & break sequences.
I actually used Tamiya painting tape and put 4 bits on top of each other on a pane of glass, then did my cuts.

Bearing in mind that the chuff sound is made on the break (not the make), I marked on the wheel where the break should be in relation to the pickup contact when the rods are TDC (Top Dead Centre - RP) as the wheel rotates forward.
I positioned the first strip radially outwards so its trailing edge was aligned with this mark. The longish length of tape makes it easy to align radially.

I then positioned the other three equidistant around the wheel.
Then I painted superglue as evenly as I could in the bare spaces between the strips.

I let it dry for a day, removed the tape and gently smoothed any raised edge where the superglue had interfaced with the tape.

I ended up with 4 nice tough break surfaces!  And nice chuff sounds when the engine runs, synchronised with the rods.
So thanks once again; your method is much easier than the 35mm film.

Best regards,

Thank you Erik it is nice to get feedback about the blog and I am glad it got you thinking to come up with this more sophisticated version of the ‘chuff cam’.


Odds said...

Surely it should be "Chuff Can", not Chuff Cam. Chuff Cam would suggest you're filming it!
In the world of toy steam, we use chuff cans, as your average Mamod doesn't make much of a chuff noise as it works, so we come up with fancy designs to make the wee engines puff a bit more.

Ray P said...


No it is a cam of sorts, used to produce a chuff with a sound decoder. usually mounted on the axle or the rear of a driving wheel. Originally they were small 4 sided cams with a wiper for timing the chuffs.

Ray P

Odds said...

Ah! That sort of cam, sorry, wrong end of stick time.......again!

John Bryan said...

Gentlemen, I am in awe of your skill, ingenuity, dedication, enterprise and attention to detail... and your willingness to share hard earned knowledge around.

Iain Robinson said...

A great idea! Very simple and yet I can imagine it would be very effective.

Ray P said...


Yes, a cam chuff is much more realistic, so often the auto generated chuffs from a decoder don't cover the whole speed range and if you can make the loco slip then your will hear that as well.