HUGE vs. TINY drive wheels - Why? | Railroad 101

I remember the first week learning about gear ratios in robotics . It became a hilarious and quickly degrading topic as my classmates and I realized how little we understood about all the factors that contributed to motion. Great video ❤️

This man knows so much about steam that a locomotive was named after him. It's called a Hyceler.

For true speed you need the GWR Hurricane with it's 10ft driving wheels

good god yes! I can finally send this to people for a quick explanation! all of the locomotive performance in steam and steel is based on the actual physical attributes of the engines. and so many times people go "but.. why can't you make this faster? why can't you make this one stronger?" Like, my brother in christ, I'd have to remodel the entire running gear for that!

What has always intrigued me were the ATSF 5001 and 5011 classes, freight engines with passenger size 74" wheels.

I used to think that narrow gauge engines were much smaller just because the track was smaller, until I read about South African Railway's Red Devil. A 3' 6" gauge 520,000 pound 4-8-4 with 60-inch drivers, that could do over 80 mph and pull a serious consist of freight. A very fascinating video, and at last a second opinion on locomotive mechanics for all of my friends who think I'm crazy! Love it!

The same concept can be applied to internal combustion engines. Some inline sixes, like the flathead six found in the Dodge M37, have a lower power band than, for example, a 2JZ. The reason for that is because the Dodge's crank throw is longer than the 2JZ. That means you can get more low-end torque, but not the top-end performance of the 2JZ.

New York Central’s L-3 Mohawks were intended for a lot of mixed traffic work and thus were fitted with 69-inch drivers, but built with the capability to have 72-inch drivers fitted if the need arose for higher speed demands. As it happened, the need wasn’t there, and the class leader (only one fitted with larger drivers) was later swapped out for standard 69-inch.

I like seeing some of the inoperable locomotives at the Museum, 20, 346, and 491 get a lot of well deserved attention for being in operating condition. However, I personally still like the static display locomotives even if it isn’t possible to run them at the museum.

This driver wheel size thing is something I already knew. In the Netherlands we mostly look at German steamlocomotives and there the differences in wheel diameters are quite big. Big wheels are for speed, the smaller ones for power. That's why a BR 01 locomotive (used for long distance passenger trains) has about 79" drivers and a BR 52 locomotive (used for freight trains) has about 55" drivers.

Hey it's me again. When you started talking about gear ratios it reminded me of a chart from one of locomotive service manuals. The manual in question was for an SD45 and it has a chart for top speeds. The gear ratios it mentioned for the D77 traction motor started at 62:15 and went to 57:20 and the top speed went from 65 to 95mph respectively. I know GE motors use different gear ratios starting at 74:18 but idk any others.

Hyce, friend, I'm now on my second watch-through with a pencil and the tractive effort equation in front of me. I'm trying to derive the equation now. This is alarmingly well-timed with the Discord discussion of the proposed Berkshire the silly Midland Terminal wanted. I'm still not sure if they wanted a fast locomotive, a strong one, or both (which seems like a poor answer to an optimization problem). Thank you for the video. Always love seeing the Museum engines and learning something.

I recently went to see a DRG Class 18, those drivers where absolutely huge at 2,1 meters. However, the crank pin was very close to the center. This video explains very well why that was!

I'm really enjoying the cuts to a wide shot you've had here and in the tunnel motor video. It gives a sense of scale to the locomotives that even a shot of standing next to the towering drive wheels doesn't provide.

After watching your video, I thought of an idea for a future video; perhaps discuss in detail the difference between an A-unit and a B-unit and perhaps show how a B-unit is controlled without an A unit.

I remember when I visited to see 5629 when I was younger and I was in absolute shock at how massive the overall size of the train. I stood next to the wheel base and it was almost a whole head taller than I was. I would love to see a train that gargantuan pulling a rake of coaches.

I go to the School of Mines in Golden with the museum being just 10ish minutes from my house, once school chills out I want to go so much and look at everything there. You've definitely got me interested in this stuff.

I love how you teach people with that amount of passion! it really drives not only trains but me also-.

It was very nice to see #4455 at the end of the video! Reminds me of her (brother/sister?) #4466 at the California Railroad Museum. I have an old railroad VHS video of when it ran (probably pre-1999).

Though I am familiar with this concept already I think you should have explained in more detail. You mention that for a given wheel to cover a distance it takes a certain amount of rotations. That's why rotating at the same speed, a wheel with smaller diameter covers less distance than a larger wheel. Forgive me if I missed it but you didn't mention the reason steam locomotives don't simply rotate smaller wheels faster is because it creates balance and wear issues due to all of the moving mass in the valve gear and the side rods. Diesels don't have all of this extra stuff that needs to be balanced so they can rotate their wheels faster. Also, steam doesn't expand instantainiously, by reducing driving wheel size you increase piston speed and if you go fast enough the piston outruns the rate the steam expands at, and so it doesn't apply enough force to the piston to accelerate more. Answerong the question a viewer might have of "why can't they make a fast engine with small wheels so it can also haul large loads?" By the way, you didn't really mention that the reason smaller wheels for a given crank offset are more powerful is because the power of one stroke of the piston has to move the train over much less distance, since one stroke is 180 degrees of rotation, the power created in one stroke always has to be spread out over the distance the wheel rolls in 180 degrees. Horsepower is (torque x rpm)/5252 so torque value supplied by a given piston will create much more power over a distance if the piston works at a higher rpm (to a point, as I mentioned, steam can only expand at a finite rate).