The Toyoda Model G Loom (with Videos)

Toyota Motor originated from the Toyoda loom factory, where Sakichi Toyoda invented looms. Probably the most famous one is the Toyoda Model G Automatic Loom. This loom touches on many points that are part of the Toyota Production System and lean manufacturing. During my last visit to Japan in September, I made some videos detailing many of the features of the Toyoda Automatic Loom from 1924. Be advised: Lots of images and videos ahead!

Introduction to the Model G

Toyoda Model G Automatic LoomThe Toyoda Model G loom, introduced to the world in 1924 by Sakichi Toyoda, was probably the most advanced loom of its time. Its quality and productivity were unparalleled. Using many mechanical gadgets, one unskilled worker was able to supervise thirty to fifty looms simultaneously. Hence it already incorporated the idea of karakuri kaizen and jidoka.

Licensing the loom to the Platt brothers (United Kingdom) generated significant cash flow for Toyoda. Legend has it that these funds were used to establish the Toyota Motor Corporation in 1937, although in reality these funds were spent on a large bonus for the employees, and Toyota Motor was established using conventional financing (and they changed the name from Toyoda to Toyota).

Model of the assembly line

While the Platt brothers initially praised the loom, they had difficulties manufacturing it due to their low-quality production. Toyoda, on the other hand, produced it very successfully and built its first assembly line for the Model G loom in 1927.

The following images are from the highly recommended Toyota Commemorative Museum of Industry and Technology in Nagoya, Japan.

Preparation of the Shuttle

The shuttle is the device that moves back and forth transporting a spool of yarn. In preparation, the yarn has to be threaded through a small hole in the shuttle. Previously this was done by putting the yarn near the hole and then sucking it through with your mouth – breathing in all the dust and dirt around the hole.

Toyoda used a neat trick by making a small, open channel in the other direction. The yarn is simply pulled into this channel. A length of yarn continues to be pulled until it breaks. When breaking, the yarn’s elastic tension rapidly snaps it in the other direction, shooting it though the hole where it was supposed to go in the first place. Watch the video below for a demonstration.

Automatic Shuttle Change

Toyoda Model G Automatic Loom Detail Automatic Shuttle ChangeAnother neat feature is an automatic shuttle change. Previously, attendants always had to monitor the shuttle to put in a new one when the old one was out of yarn. Forgetting this wasted machine time and degraded the quality.

The Model G loom has a feature that detects an empty shuttle, and exchanges it with a new one.

The spool of yarn inside the shuttle has a slot. A pin in the machine presses against a piece of wood, attempting to push it into this slot. As long as there is yarn on the spool, the yarn prevents the wood from entering the slot. If the yarn is used up, the wood can enter the slot. A mechanism detects this, and ejects the old shuttle while pushing in the new shuttle. Watch the video for the different mechanisms in action. Please note that this is a mixture of videos of a full-sized Model G loom, different museum visualizations, and even some older looms preceding the Model G while the technology was developed.

Pin in the lower left sensing status of shuttle in machine

The Warp-Break Auto-Stop Mechanism

One major problem with looms is breakage of yarn. The two types of yarn are called warp and weft. Both of them can break, creating significant quality and productivity problems. Previously, many workers were kept busy merely looking out for broken warps.

Toyoda Model G Automatic Loom Detail Warp Break StopThe Model G loom solved this nicely. A small piece of sheet metal is hanging from every warp. The tension of the warp keeps this sheet metal up. If the warp breaks, however, the tension goes away and the sheet metal drops down.

This dropped sheet metal then blocks a bar moving back and forth underneath the sheet metals. The stopped bar subsequently activates another mechanism that eventually turns the machine off. Watch the video to see the mechanism in action. Please note that this is a mixture of videos of a full-sized Model G loom, different museum visualizations, and even some older looms preceding the Model G while the technology was developed.

The Weft-Break Auto-Stop Mechanism

Just as a break in the warp disrupts quality and productivity, so does a break in the weft. Here too, Toyoda solved this problem with a device that stops the machine automatically if the weft breaks. This is done using a weft fork.

The shuttle with the yarn runs within another part back and forth. This part is called the race. The race moves back and forth. In the picture, the race would be the reddish wood in the lower half.

Parts for the weft fork

The weft’s three-pronged fork squeezes the yarn (the weft) against a metal grill. In the image, you see the weft fork in the center and the grill to the right of the center. The fork moves through the gap of the race.

If there is yarn (the weft), the fork cannot go through the grill due to the tension of the weft. However, if the weft is broken, the fork can pass through the grill. A subsequent mechanism detects this movement and turns off the machine. Unfortunately, there was no display model for the weft fork, hence I have no video for this mechanism.


One famous feature of the Toyota Production System is the andon. In modern times this is often a digital display board telling you how much was produced, and how much you still need to achieve the target. Simpler forms of andons are stacked lights in different colors, indicating the status of the machine. Green is usually good, orange is a warning, red is a bigger problem, and so on.

The Toyoda Model G has a very early pre-digital, even pre-electric version of the andon. Not all looms but at least one per cluster of looms had a movable indicator that could be either off, white, or red as shown below. The indicators were not flat metal, but had a perpendicular metal too, so that the status could also easily be seen from the side. You could even signal both white and red, but this would be confusing signals from different sides.

Pre-electric andon off, white, or red

Overall, the Toyoda Model G loom included many of the aspects that the Toyota Production System is famous for. I hope you liked this deep dive into production history, and I hope you also liked the videos. Many thanks to the team from Lightworks for giving away a free and powerful video editing software. Also many thanks to the Toyota Commemorative Museum of Industry and Technology for their awesome exhibits! Now go out, learn from history, and organize your industry!

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