What is the RPM range of OO/HO wheels?

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meehow
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What is the RPM range of OO/HO wheels?

Postby meehow » Tue Jun 08, 2021 12:27 pm

What is the RPM range of OO/HO wheels?
I could probably calculate it somehow!
Hopefully someone knows outright.
Model trains simulate speeds 0-100mph and at HO scale this translates to RPM of 0-???

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luckymucklebackit
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Re: What is the RPM range of OO/HO wheels?

Postby luckymucklebackit » Tue Jun 08, 2021 1:05 pm

Should be simple enough to calculate, you need to measure the wheel diameter, from which you can calculate the circumference, then measure a known distance on the track and time how long the loco takes to cover that distance. Then divide the distance covered by the circumference to get the number of times the wheel turned, then divide that by the time taken.

For example: measured length is 2m = 2000mm, wheel diameter is 16mm so circumference is 16 x 3.14 = 50.24mm, therefore the wheel will turn 2000/50.24 = 39.8 times in that distance. if it takes 10 seconds to cover the 2m the rpm is 39.8/(10/60) = 238.8 rpm

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meehow
Posts: 33
Joined: Mon Apr 12, 2021 8:57 pm

Re: What is the RPM range of OO/HO wheels?

Postby meehow » Tue Jun 08, 2021 1:33 pm

thank you.
awesome! i will try.

how to calculate the correct speed on track? assuming 50mph simulation.

Bigmet
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Re: What is the RPM range of OO/HO wheels?

Postby Bigmet » Tue Jun 08, 2021 2:00 pm

If you scale speed linearly (and not all modellers choose this approach) then in OO the model travels 1/76 of the distance the real one does, in the same time.

The rpm of the wheels is exactly the same, model and prototype, provided the model is accurate. In the 120+ mph/ 200+ kph range that was top speed for steam, the driving wheels which were typically of 80"+/ 2.1m diameter, were going just over 500 rpm. (Of more concern was the stroke frequency, each piston running in the range of about 8Hz, this made for an uncomfortable vibrational environment for the footplate crew; and the uneven weighting of the driving wheels would lift the tyres clear of the track for a period in every rotation.)


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