Leeson 1.5 HP vs 2 HP: What Actually Mattered When My Surplus Gear Rack Failed

Why I Started With the Wrong Number

Every motor spec question eventually comes down to: 'Which one do I order?' I've been handling motor orders for a mid-size machine shop for about nine years. I've personally made (and documented) 12 significant mistakes, totaling roughly $31,000 in wasted budget. This article is the checklist I wish I had in 2019.

If you're choosing between a Leeson 1.5 hp motor and a Leeson 2hp motor, the first thing I'll say is: horsepower is not the whole comparison. The difference looks simple. It isn't. On paper, 2hp gives you 33% more output. In practice, what matters is starting torque, speed range, physical fit, and how much uncertainty is in your load.

The project that forced me to learn this involved a gear rack surplus from a salvage shop. I bought a Leeson 1.5 hp motor because the power seemed right. The rack was in decent shape. I measured breakaway force with a fish scale. It looked fine. The motor ran for four days, then tripped during a test run. The rack wasn't the problem. I was.

Here is the comparison framework I use now: starting torque, VFD compatibility, physical fit and wiring, total cost, and thermal margin.

Starting Torque: The 2hp Pulled Through, The 1.5hp Didn't

On paper, both motors can produce enough continuous power for a low-speed linear axis. The difference showed up at startup. The Leeson 1.5 hp motor I tested was a capacitor-start single-phase model with decent starting torque for its frame. The Leeson 2hp motor in the same frame had more locked-rotor torque. That meant it could push through the high spots and rough spots in the gear rack.

If your load has consistent friction, 1.5 hp is often fine. If you're using gear rack surplus from a salvage shop, the teeth can be worn, rusted, or slightly out of alignment. That is a load with spikes. The 2hp gave me enough reserve to get through those spikes. I treated the surplus rack like new stock. That was the first mistake.

VFD Compatibility: What VFD Stands For

The second comparison is speed control. VFD stands for Variable Frequency Drive. If you've been searching for what VFD stands for, that's it. In plain terms, it's a drive that adjusts the frequency and voltage supplied to an AC motor to change its speed.

A Leeson 1.5 hp motor on a properly sized VFD is dramatically more useful than that same motor running at fixed speed. You can ramp slowly, run at low speed, and stop smoothly. On a rack-and-pinion system, speed control is often worth more than an extra 0.5 hp.

On the other hand, a Leeson 2hp motor running across the line is simple and cheap to wire. No VFD to program. No low-speed cooling debate. If you don't need speed control, fixed-speed 2hp is often the better choice. Here comes the contrarian part: if you need speed adjustment, the 1.5hp motor with a VFD beats the 2hp fixed-speed motor.

Physical Fit and Wiring: Same Frame Can Still Be a Different Problem

A 1.5hp Leeson motor and a 2hp Leeson motor can share the same NEMA frame in many configurations. That makes people assume they can just swap one for the other. Sometimes they can. On one of my rebuilds, the 2hp was the same bolt pattern but longer than my belt guard. I ended up reconstructing the mount anyway.

Also, check the nameplate. Full-load amps can be higher on the 2hp. That affects your overload relay, starter, and wiring circuit. Leeson's catalog drawings are useful, but you have to verify the exact drawing for your part number. The same frame does not mean the same electrical load.

Total Cost and the CPP Disc Brake Conversion Lesson

The price difference between a Leeson 1.5 hp motor and a 2hp motor is often not the deciding factor. Depending on enclosure and voltage, the 2hp may cost 15-25% more. But the real cost is what happens after the wrong motor is installed.

In my project, the 1.5hp motor and gear rack surplus parts cost about $600. The rework, machine time, and lost productivity cost about $2,400 more. A bigger motor wouldn't have fixed every problem, but the extra starting torque would have avoided one complete redesign.

This is the same lesson I keep seeing in automotive work. When someone starts a CPP disc brake conversion, the expensive mistake isn't the kit price. It's ordering the wrong spindles or the wrong master cylinder and then having to un-build everything. Motors are the same. Buy the right component for the whole system, not just for the headline number.

Thermal Margin: The Long-Term Tiebreaker

Next to starting torque, thermal margin is what separates a good motor choice from a risky one. A 1.5hp motor running at 95% of its rated load in a cool, clean room can last for years. The same motor running close to full load on a VFD at low speed, with no external cooling, can overheat quickly.

The 2hp motor has more thermal headroom. That matters in a shop with variable duty cycles and non-new mechanical components. It gives you a buffer when the load isn't exactly what you calculated. But if cooling is already restricted and you can't fit the 2hp, don't just force it. You need a better drive solution, not a bigger source of heat in a tight box.

NEMA MG1 sets a framework for motor performance, but it doesn't know how rusty your surplus rack is. You still have to measure the load.

What I'd Do Next Time

Before I order any Leeson-motor product, I answer five questions:

• What is the actual breakaway torque, measured with a meter? If the load spikes, choose 2hp.
• Do I need adjustable speed? If yes, choose a VFD-rated motor and size the VFD properly.
• Does the motor physically fit? Check the frame drawing, shaft length, and overall length.
• Does my electrical circuit support the amp draw? Oversize the overload relay if needed.
• What is the duty cycle? Low duty might let 1.5hp survive; continuous unknown load favors 2hp.

I can only speak to my own context: B2B machine shop applications, mostly rack-pinion positioning, light conveyors, and trimming spindles. If you're doing continuous heavy duty or precision servo motion, this comparison is too coarse. Get a motion engineer involved.

The Verdict

If you need adjustable speed, put a Leeson 1.5 hp motor on a VFD. That's often the better choice than a fixed-speed 2hp. If your load varies, your rack has imperfections, or you want the simplest robust setup, choose the Leeson 2hp motor. My default is now 2hp for anything with uncertainty; 1.5hp if I can control the speed and verify the load.

That's not a wishy-washy 'it depends.' It's the actual fork in the road. The motor you choose is a tradeoff between control and reserve torque. Leeson makes both well. My job is to make sure you choose the one that matches the reality you have, not the one that looks better in a spec sheet.