The Joy of Chuff

[753]

Setting up the sound on the Armstrong I was not happy with the chuff chuff compared with the speed. I like to see engines run at an elegant speed so it is low geared I then realised there was a way to sync the speed with the chuff sound.
I fitted a disc with two small magnets set at 180deg (as it's a two-cylinder engine) to one of the tender axles and a reed switch in close proximity then connected the wiring into the sound card and hayho it works
A truly joyous moment with the speed and chuff of the engine in perfect sync.

Mike

[Doddy]

I fitted a disc with two small magnets set at 180deg (as it's a two-cylinder engine)

Nice job Mike, but just remember with two cylinders and the offset wheel quartering you get four beats per wheel revolution on a two cylinder locomotive.

ATB

Robert

[cabbage]

The G3 WIKI contains the scad file for a 4 beat chuff cam
This uses a cheap roller microswitch.

Regards

Ralph

[753]

Doddy

You are quite right on the no of beats will amend the cam and chuffs.

Mike

[Nick]

Mike,

Forgive me if I'm being dim, but aren't the tender wheels a different diameter from the loco wheels so that the chuff sound isn't synchronised with the loco wheels? I'm not an electronics person so I struggle with this stuff.

Nick

[AshleyW]

if it's the soundcard with the tv remote for setting chuffs, then you can watch the driving wheels and set the chuff to match, even if on tender axles. i had a problem that the soundcard was for 12v and the loco was 24v, so the chuffs seemed very fast and even with plus/minus on remote, i could not marry it up. the only way round that was to allow the wheels to turn a revolution or two, then press the power button to get a strating point somewhere near . once set up nicely it's very pleasing.
p.s my german speaker had no mount. i found the lid of a roll on deodarant perfect for taping the speaker into ! i then had a square of foam, cut a cross into it to force the deo cap/speaker into, then slid the speaker down the boiler into the smokebox,so it was pointing up the chimney. i then trapped the slightest amount of the mount foam in the smokebox door to ensure it stayed in place.

[753]

Well, the plot thickens Doddy is correct that a two-cylinder engine has four exhaust beats per one revolution of the driver wheel, Nick is also correct that the dia of the driver wheel needs to be considered. What is more important is the dia of the trigger cam as this produces the chuff
To achieve a true representation of the exhaust beat you would need a tigger cam disc the same dia as the driver with four trigger points, this is not possible on my loco, however a cam disc half the dia with two trigger points driven at twice the speed would give the same result. But the cam is fitted to the tender axle, although the tender wheel is smaller than the driver it does not give twice the required speed.
So, making the cam disc smaller than half the dia of the driver compensates for the difference, I am now truly chuffed!!

Mike

[Nick]

Thanks, Mike, all is now clear.

Nick