MTH chuff rate

If both sets of drivers (engines) were in sync then 4.  When ,most of the time, the drivers are out of sync it would be some cadence  of 8.  Now some of MTH's sound sets may have incorporated this??.  I know some of Lionel's did.  The rate would shift back and forth between 4 and 8 as would be prototypical. 

A rate of 6 would apply to a 3-cylinder  engine such-as an UP 9000.

Ron

Four.

The Big Boy is two, 2-cylinder engines mounted on one locomotive.  So the correct sound setup is four exhausts per revolution. As the two engines drift in and out of sync it will sound like more than four at times, but the basic setup is four.

3-cylinder steam engines would have 6 exhausts per revolution.

Most sound sets add the second set of cylinders, so 4 chuffs/rev is typically the correct setting.

thanks for he info!

Paul

Statistically there is a FAR more chance of some cadence of eight then one event of perfect or near perfect Synchronization. 

The DVD I have of all Big Boys clearly reveals this.  Of course this is true for all simple articulated steam engines.  

May not be true for single frame European steam engines that had four cylinders that could be operated as simple or compound.  But that would also depend on how these pistons were "Quartered" in relation to each other.

PRRronbh posted:

Statistically there is a FAR more chance of some cadence of eight then one event of perfect or near perfect Synchronization. 

A lot depends on the speed and the condition of the tires on each engine. I remember when UP Challenger #3985 received all new tires on both engines, she would work into synchronization at about 25 to 30 MPH. Then she was pretty much 4 exhaust up to 70 MPH. I've also witnessed N&W #1218 do the same.

The DVD I have of all Big Boys clearly reveals this.  Of course this is true for all simple articulated steam engines.

Again, it depends on the speed. Starting, pretty much any/all simple articulated locomotives will exhibit the 8 exhausts per revolution, until they work themselves into synchronization as a result of the power pulses and vibrations.  

May not be true for single frame European steam engines that had four cylinders that could be operated as simple or compound.  But that would also depend on how these pistons were "Quartered" in relation to each other.

 EDIT:  

I should have pointed out that MTH seems to have developed the best simple articulated in-and-out of synchronization of the 4-chuffs, as the speed of the model increases. Then the "synchronized 4-chuffs" stays at higher speed, changing back to the in-and-out of synchronization as speed reduces.

Just to add as a footnote: a compound 4-cylinder loco like the USRA 2-6-6-2 or 2-8-8-2 sound like 2-cylinder locos because only the low-pressure cylinders exhaust to the atmosphere (the stack). There is no syncopation with the compounds as there is with the BB or other simple 4-cylinders, something that our models have often gotten wrong. This "simple" syncopation is really not heard above low speeds, anyway, it seems to me.

Also, some US 4-cylinder compounds could be operated in simple or compound mode; it is not a "European" feature.