While a lawnmower is (usually) ready to hit the ground running fresh out of the box, there are special factors that may necessitate some minor tweaks. Blade spin speed is just one of the things a mower owner might want to change but is it possible?
Mower blade spin speed can be manually adjusted on some mowers and an included feature in others. It is accomplished by calibrating belts, gears, or pulleys. Most manufacturers advise against the practice and the warrantee could be void if you attempt it. Check your user’s manual for details.
Today we will explore the ways you can amp up your mower blade’s revolutions. We will also look at the issue of “free-spinning”, and whether you should worry about it. Finally, we will discuss engine RPM and its effect on your lawnmower’s engine life. Let’s go!
Contents
Is It Possible To Make A Lawnmower Blade Spin Faster?
Before we answer this question, we must briefly talk about why manufacturers set their mower blades at the speeds that they do. There are some fairly serious safety risks in exceeding recommended speeds.
The materials used in mower construction are designed to withstand a limited range of forces placed on them. Rotating mower blades faster than their intended use could put mower operators or bystanders as serious risk.
Why Some Mowers Are Not Designed For Adjustable Blade Speeds
The first reason is safety. The American National Standards Institute (ANSI) restricts all commercial and private mowers (walk-behind or garden tractors) to a maximum blade speed of 19,000 feet per minute. Major manufacturers agree that this speed is more than enough for cutting grass.
This ANSI standard is based on the perception that most mower decks would not be able to stop a blade spinning faster than 19,000 fpm were it to come loose. Also, blades at this speed or higher can turn simple debris like rocks into hazardous projectiles if they make contact.
The second reason why (most) manufacturers would rather you didn’t tamper with your mower blade speed is vibrations. Making your blade spin faster than it was meant to may lead to excessive vibrations in the deck, engine, connections, and any other delicate parts of your mower. This could put you at risk of warranty voidance.
A mower is designed for its own power level at a good cut setting. A good mower speeds up with help from the governor in higher grass.
Jerry McMillan, McMillan Lawn Service, 40 Years Experience, Great Grandpa
Now that we’ve established why blade speed adjustments are discouraged, let’s look at how you can go about it if you insist anyway.
If you like this article about mower blades, you will no doubt like these…
How Can Blade Speeds In Mowers Be Increased?
Try the throttle.
Jerry McMillan, McMillan Lawn Service, 40 Years Experience, Great Grandpa
(Yep, Jerry has grandpa jokes.)
The truth is making your mower blade spin faster is not so simple and some manufacturers make use of measures to prevent owners from doing so.
However, you can change blade spin on other types of mowers, although it may be a bit tricky.
Belt Drive Mowers And Adjustable Blade Speed
Belt drive mowers with horizontal blades that are driven by the mower engine’s RPM are the easiest to modify for faster blade speeds. Such mowers have no gears that allow the independent operation of the engine and mowers i.e. if the engine is running, the blades stop spinning. A lot of older walk-behind mowers are like this.
To increase blade speed on a gearless belt-driven mower, you must increase the engine’s RPM. This process involves modifying your mower’s governor arm and spring. These two parts link with the mower’s carburetor to produce higher or lower RPM.
The higher the tension on the governor spring, the greater the pull on the carburetor and, therefore, the greater the engine’s RPM. To adjust spring tension, you can use a pair of pliers to twist the part of the governor arm that connects to the spring.
To increase tension, twist the governor arm away from the spring. Upon running the mower, you should notice the mower running quicker. The opposite is true if you want to decrease RPM. Simply twist the governor arm toward the spring to loosen the tension to make the engine run slower.
Gear Operated Cutting System Adjustability
Some brands, like YBravo, also allow you to increase RPM on walk-behind mowers that use gears. This is facilitated by an apparatus known as a blade belt clutch (BBC), which allows the engine to run while the blades are still.
Adjusting blade speed on such mowers involves accessing the BBC cable, which is usually hidden under a panel above the mower deck. To increase RPM, simply undo the nuts holding the BBC cable in place and reposition it. Pull the cable taut to increase blade speed, or slacken it to slow the blades down.
Increasing Blade Speed On Belt And Pully Mowers
You can also increase blade speed spin on riding mowers that incorporate belts and pulleys. This is done by replacing your blade pulley with a smaller one, and your drive pulley with a larger one. It is important to note that while the blades may spin faster, the mower’s cutting quality may be adversely affected.
While the blades are an important part of cutting grass, other factors like the mowing deck also contribute to a mower’s ability to cut grass well. All of these factors are well optimized and employed in proper balance to make the best mower possible.
Should Lawnmower Blades Spin Freely?
Yes…and no.
Blades on gearless mowers should not move freely at all because their movement is directly dependent on the running of the engine. The blades are held by a belt system that connects directly to the motor.
A freely spinning blade on such a mower may be a sign of a loose connection to the shafting point. This is very bad because continued operation of such a mower could eventually lead to the blade flying off and causing unimaginable damage.
Mowers with a clutch should have blades that spin freely. Blade operation is not dependent on the engine, as the operator can engage or disengage the mower deck and belts anytime. In fact, if your mower blades are not moving freely, it may point to problems with your mower’s transmission.
One thing your blades must never do (regardless of the presence or absence of a clutch) is touch the sides of the mower deck.
Does Faster RPM Destroy The Engine?
DIY blade speed increases will almost certainly cause damage to your engine over time. Unless your manufacturer provides a facility for you to vary your RPM, doing this will cause problems or even void your warranty.
A lot of manufacturers are very touchy when it comes to “their” engines…and understandably so. Innumerable hours (and dollars) go into researching engine balance and producing motors with the best performance for each of their mowers.
Mower owners are, therefore, advised to avoid tampering with their engine’s RPM because causing it to go faster will increase vibrations running through the engine, which could loosen other parts and connections.
The faster operation will also have an adverse effect on your fuel efficiency. A motor with a high RPM will also use up oil faster, which is also a problem. You will also need to carry out service more frequently.
You can also forget about your expected engine lifespan. If your mower is still on warranty, be very careful because some manufacturers are very unforgiving with this.
The Final Touches On How To Make A Mower Blade Spin Faster…
The can and should of speeding up the blades of your mowers are two different considerations. It is possible to do it, but the benefits are relatively low in the short term.
In the long term, the increased expense and wear and tear on your equipment makes it not only dangerous to you, but also to your mower.
If you absolutely need greater blade speed, try to get a mower that has built in options for it. Otherwise you could be risking voiding your warrantee or even worse… injuring yourself or others.
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References
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