Question for the Jack experts.

[Bear]

Seeing different versions of the STO yellow jacks pop-up on Ebay, it's easy to see how they can be confusing with different weight ratings. Since they look similar on the exterior, what's the differences on the inside that makes them able to support more weight? Is it the number or size of the ball bearings? Different compostion of the materials? A thicker case?

Thanks in advance.

 

[jblatz]

The difference is the extended height. Since taller jacks have longer extensions, the taller the jack, the lower the weight rating. This is counter-intuitive, and certainly leads to confusion.

Consider the tall jacks in @treerootCO jack collection. The 4th and 5th jacks from the left are 09110-13010 rated 0.7ton (1543lbs). The red jack in the corner is 09110-31020 rated 1ton (2204lbs). The tall jack just to the left of the red one is 09110-21020 also rated 1ton. The remaining short jacks are rated 2ton (4409lbs).

The Toyota cast jacks that are rated 2ton or less have the same design more or less. Some are single stage with manual extension, some are 2-stage. Some are taller others shorter. The internals are pretty much the same. The FJ25 jack (RK30-91100) and the early FJ40 jack have a larger base and larger bearing balls (although fewer) than the later FJ40 jacks. But this difference did not affect the rating, the FJ25/FJ40 jacks are all rated 2ton.

The extended height makes a difference in weight rating due to buckling failure. Jacks can fail due to crushing where the load overwhelms the strength of the material. But when the jack is extended, buckling is the concern. When the load isn't perfectly aligned, the jack column starts to bend, creating more mis-alignment, eventually collapsing to one side or the other.

An extended jack can be viewed as an upright column. Euler's critical load formula can be used to calculate buckling stress in columns. One version of the formula is this. l is the length of the column, C is the elasticity of the cross-section. If the length doubles, then the critical load P is divided by 4. So increasing the length of the column (extended height of the jack) significantly reduces the critical load (weight rating) where the column buckles. So taller jacks need lower weight ratings.

That isn't to say there aren't short jacks with low weight ratings. 09110-27010 is a 2-stage jack, similar in size to 09110-26010 (rated 2ton), which is the left-most jack in the group picture above. For some reason 09110-27010 is rated 1.5ton (3306lbs). Of course, Toyota only needs to rate the jack for its intended use with specific vehicle(s). There's no benefit to rating it higher, even though it may effectively be a 2ton jack.

 

[middlecalf]

Yeah baby! Euler’s formula finally made it into a tech thread.

 

[Bear]

@jblatz ,

Thank-you for the explanation of critical loads. A couple further questions, understanding of course none of this is offering legal judgements:

Jacks and their accompanying accessories can and do get moved around from their original vehicles.

Since none of the 40-series jacks were/are intended to jack up the entire vehicle at once, are jacks rated at 2 tons even necessary? Specifically, would some of the lower-rated STO jacks be sufficient to be safely used as 40-series jacks?

From a design standpoint would a wider base footprint, a thicker outer casing, or a beefier inner gear have any effect on the supporting capacity of these jacks?

Noticing the variances in the diameter size and number of the ball bearings in the 2 ton jacks, do the bearings have much effect on the weight ratings?

Is it your understanding that automotive jacks are rated at a certain percentage of their overall capacity, much like ladders provide extra steps not intended for standing?

Is cast iron a better material for these jacks as opposed to the steel stamped ones?

Thank-you again for your insight.

 

[JackA]

@jblatz ,
Is cast iron a better material for these jacks as opposed to the steel stamped ones?

For trail use, I prefer the stamped ones. The cast ones can crack and the ears break off. For original style and light use, I like the cast.

 

[Bear]

Still wondering about how the construction and components of the STO jacks affects their capacity ratings as asked in Post #4 above.

 

[jblatz]

Since none of the 40-series jacks were/are intended to jack up the entire vehicle at once, are jacks rated at 2 tons even necessary? Specifically, would some of the lower-rated STO jacks be sufficient to be safely used as 40-series jacks?

Not clear how Toyota determines the appropriate jack rating for a vehicle. From a few examples, it appears they use the curb weight and round up. The 09110-13010 jack is rated at 0.7tons (1543lbs). It was used in the Toyota Publica, curb weight 585kg (1279lbs). 09110-35011 Land Cruiser jack is rated 2tons (4409lbs), curb weight 3263lbs (FST), around 3800lbs for the hard top. So the numbers suggest a lower rated jack could be used to lift part of the vehicle. Whether it could be done safely would depend on the particular jack, the condition of the jack and the task at hand.

A couple of considerations for the STO jacks. Those cast jacks are now all over 40 years old, and subject to who-knows-what wear and tear. So some may not be up to the task. Storing other STO jacks in Land Cruisers can be an issue since many of the lower rated jacks are taller, they won't fit the jack brackets.

From a design standpoint would a wider base footprint, a thicker outer casing, or a beefier inner gear have any effect on the supporting capacity of these jacks?

All those play a role. You can see this with the STO 5ton jacks. They are much bigger and heavier than the 2ton jacks. The examples I've seen appear to be very early, pre-1954, since they don't have the JIS mark. The JIS jack standard was introduced in 1954. I'll get some pictures that show both the 5ton and 2ton jacks for comparison.

Not clear if or where Toyota used these larger mechanical jacks. The heavy truck owners manual from around 1958-60 shows a 10-ton hydraulic jack. The Toyota hydraulic jacks I'm aware of 09110-36051 (5ton), 09110-36160 (4ton), and 09110-55020 (10ton) are all made by KYB.

Noticing the variances in the diameter size and number of the ball bearings in the 2 ton jacks, do the bearings have much effect on the weight ratings?

Considering just Land Cruiser jacks, the ball bearings don't seem to have much effect. The RK30 jacks and early -35011 jacks used larger bearings than the later -35011 jacks. But all were rated at 2ton. Will be interesting to see what bearings are in the 5ton jacks.

Is it your understanding that automotive jacks are rated at a certain percentage of their overall capacity, much like ladders provide extra steps not intended for standing?

The Japanese jack standard tests jacks several ways: 1) repeated raise/lower at 120% of rated value, 2) while fully extended, at 150% of rated value for a designated amount of time 3) while inclined and fully extended, at rated value for a designated amount of time. The rated value is considered the maximum working load.

Is cast iron a better material for these jacks as opposed to the steel stamped ones?

"Better" can have several dimensions: stronger, cheaper, more robust, aesthetically pleasing, etc. Cast iron is harder and more brittle than steel. Cast iron tends to fail abruptly where steel deforms before failing. I suspect steel jacks are cheaper to manufacture. The steel jacks are utilitarian, the cast jacks have their retro style.

 

[Bear]

@jblatz ,

Thank-you for such an excellent explanation and education. My questions originated from seeing sellers offering the .7Ton STO jacks as "OEM for FJ40" and wondering if they were up to the task, as well as viewing the brown steel jacks used in later 40-series as a cheaper substitute for the cast iron units.

As a safety item, automotive manufacturers are aware of the liability they face for miscalculating anything to do with their jacks and their operation. With today's aftermarket flooded with Chinese products and their lack of manufacturing responsibility, we would all be better served to avoid any substitutes that may not meet or exceed the specs mandated by the vehicles' manufacturers.

Great job, much appreciated !

 

[jblatz]

@jblatz ,

Thank-you for such an excellent explanation and education. My questions originated from seeing sellers offering the .7Ton STO jacks as "OEM for FJ40" and wondering if they were up to the task, as well as viewing the brown steel jacks used in later 40-series as a cheaper substitute for the cast iron units.

As a safety item, automotive manufacturers are aware of the liability they face for miscalculating anything to do with their jacks and their operation. With today's aftermarket flooded with Chinese products and their lack of manufacturing responsibility, we would all be better served to avoid any substitutes that may not meet or exceed the specs mandated by the vehicles' manufacturers.

Great job, much appreciated !

Those 09110-13010 .7ton jacks show up all over with premium price tags as FJ40 or Land Cruiser jacks. 150% testing of a .7ton rating, would be 1.05ton or 2314lbs. Storage can be a problem.

Won't fit here...

or here...

or here...

or here...

might fit here.

 

[jblatz]

I'll get some pictures that show both the 5ton and 2ton jacks for comparison.

@Bear, following up on that earlier post, here's the STO early 5-ton jack vs. the Land Cruiser 2-ton STO jack.

Characteristics​	5-ton​	2-ton​
Rating​	11,023 lb​	4,409 lb​
Height​	10.5 in​	8.25 in​
Base​	8.5 x 6.25 in​	5.5 x 4 in​
Weight​	20lb 8oz​	8lb 15oz​

 

[Bear]

Thank-you, @jblatz ! Excellent documentation.