Building the Lightest String Trimmer EVER!

Building the Lightest String Trimmer EVER!

Written by: Mary Clementi

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Published on

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Time to read 5 min

Building the Lightest String Trimmer EVER! (A DIY Petition to Stihl)

Imagine wielding a string trimmer so light, you could tackle your yard work without the usual aches and fatigue. For many, that dream is just out of reach because existing string trimmers can be heavy and cumbersome. The folks at Main Street Mower decided to do something about it. Their mission? To create the lightest possible string trimmer by combining the best parts from existing Stihl models. Their goal is simple: demonstrate the demand for a lightweight string trimmer and encourage Stihl to bring it to life.

Understanding the Challenge: Weighing the Contenders

Before diving into the build, let's look at the contenders. Main Street Mower evaluated three popular Stihl models to see where they could shave off weight.

Setting the Baseline: The Stihl FS 91 R

The  Stihl FS 91 R  is a popular choice, but it's not exactly known for being lightweight. As a baseline, the FS 91 R weighs in at 13.6 lbs straight out of the box (without fuel).

The Lightweight Contender: The Stihl FS 111 RX

Next up is the Stihl FS 111 RX . The "RX" in the name signifies that this model was designed with weight reduction in mind. To achieve this, Stihl made several components lighter:

  • The handle is lighter.
  • The guard is lighter.
  • The gearbox is lighter.

Interestingly, the motor in the FS 111 RX is the same weight as the one in the FS 91. Despite this, the FS 111 RX manages to weigh 12.39 lbs, making it about 1.2 lbs lighter than the FS 91 R.

The Underdog: The Stihl FS 94 R

The  Stihl FS 94 R  might be considered the underdog in this comparison. It has less power than the FS 111 RX, but it's known for its reliability and is well-suited for everyday trimming around normal-sized yards. The FS 94 R tips the scales at just 11.34 lbs, making it the lightest of the three models.

Analyzing the Weight Distribution

One key observation is that the FS 94 R's lighter motor allows for less compromise in the weight of other components. On the other hand, the FS 111 RX uses lighter components to compensate for its heavier motor. This raises an interesting question: what if you could combine the best of both worlds?

Project "Frankenstein": Disassembling and Weighing Individual Components

Now comes the fun part: creating a Frankenstein trimmer! Main Street Mower disassembled each trimmer to identify the lightest components.

Important Disclaimer: Don't try this at home! String trimmers can be dangerous, and this modification could void your warranty.

The Drive Shaft

The first step was to remove the head of each string trimmer to access the drive shaft. The team also mentioned a braided shaft from an edger as a potential weight-saving option, but noted that it's more expensive. Here's how the drive shafts stacked up:

  • FS 91 R shaft: 80.2 weight units.
  • FS 111 RX shaft: 42 weight units.

The FS 111 RX shaft is significantly lighter and slightly thinner than the FS 91 R shaft. Both shafts have a steel base, but the exact composition differs.

The Guard

Next, they compared the trimmer guards. The FS 94 R guard is thinner and lighter. The FS 111 RX guard is opaque and features fewer mounting screws with an integrated hook system. The weights were as follows:

  • FS 94 R guard: 0.56 weight units.
  • FS 111 RX guard: 0.45 weight units.

These small differences might not seem like much, but they add up!

The Gearbox

The gearboxes also had notable differences. The FS 94 R gearbox is metal with a fastening screw and a large metal plate. The FS 111 RX gearbox uses a plastic portion, two mounting screws, and a hook mechanism. Here's how they weighed in (with screws):

  • FS 111 RX gearbox: 1.50 weight units.
  • FS 94 R gearbox: 1.98 weight units.

The FS 111 RX gearbox offers a significant weight reduction.

The Handle

Moving on to the handles, the FS 94 R handle uses thicker plastic, two mounting screws, and thicker metal hardware. The FS 111 RX handle features thinner plastic, one mounting screw, and a thinner band style. The weights were:

  • FS 94 R handle: 0.44 weight units.
  • FS 111 RX handle: 0.28 weight units.

The thinner plastic and hardware of the FS 111 RX handle contribute to its lighter weight.

The Engine

The FS 111 RX incorporates lighter components to compensate for its heavier engine. Let's look at the raw engine weights:

  • FS 94 R engine: 6.56 weight units.
  • FS 111 RX engine: 8.36 weight units (1.8 lbs heavier).

The FS 94 R engine is the clear winner in terms of weight.

The Outer Shaft

Finally, they compared the outer shafts (without the drive shaft):

  • FS 111 RX outer shaft: 1.37 weight units.
  • FS 94 R outer shaft: 1.18 weight units.

Based on this, the FS 94 R outer shaft was chosen for its lighter weight.

The Moment of Truth: Assembling and Weighing the "Frankenstein" Trimmer

After all the weighing and comparing, it was time to assemble the ultimate lightweight string trimmer.

The Recipe

Here's the list of components used in the final build:

  • FS 94 R engine
  • FS 94 R outer shaft
  • FS 111 RX inner shaft
  • FS 111 RX handle
  • FS 111 RX gearbox
  • FS 111 RX guard

The Build Process

With all the parts selected, Main Street Mower reassembled the trimmer.

The Final Weight

So, what did the Frankenstein trimmer weigh? Drumroll, please...

10.31 lbs!

That's right, by combining the lightest components from each model, they created a string trimmer that was even lighter than the original FS 94 R. A pound of weight savings might not seem like much, but it can make a huge difference over hours of use.

The Call to Action: A Petition to STIHL

Imagine a world where Stihl offered a whole new product line of lightweight tools! Think lightweight edgers, hedge trimmers, and even pole saws. To make this a reality, Main Street Mower is calling on you to take action.

If you'd love to see Stihl create lightweight versions of their tools, like this FS 94 RX, show your support! Give the video a like and leave a comment expressing your interest. Main Street Mower is committed to sharing your feedback with Stihl, so your voice can be heard.

What kind of lightweight tool would you like to see Stihl make?

Take a look at the Stihl FS 111 RX String Trimmer with Easy Start , the Stihl FS 94 R Professional Brushcutter and Grass String Trimmer , and the Stihl FS 91 R Professional Weed Trimmer/ String Trimmer .

Conclusion: Make Your Voice Heard!

Your feedback can help shape the future of Stihl's product offerings. Leave a comment, share this post, and let Stihl know that you want lightweight tools. Who knows, maybe one day we'll all be using a production model FS 94 RX!