Talk:Christie suspension

Illustrations
A few pictures of tanks that use this suspension design, while all very interesting, don't really fulfill this entry. What the article REALLY needs is photographs -- or better yet, diagrams -- of the suspension itself. 76.226.91.83 11:28, 21 October 2007 (UTC)

company name?
no mention of U.S. Convertable systems ?Brian in denver (talk) 19:20, 9 December 2008 (UTC)

features
isn't a further key feature the fact that instead of having lots of littel track guide wheels for the top and the bottom of the track, Christie tanks have 4 - 6 large wheels of the same size as the drivers, with the one intermiediate wheel guiding both the top and the bottom of the track?Engineman (talk) 01:43, 10 December 2008 (UTC)

Performance
The article claims superior off-road performance compared to leaf spring suspensions. However, in Panzer II it is said that the Ausf. D and E of that tank was constructed with Christie suspension, but were later withdrawn for poor off-road performance / speed, with later models returning to the original leaf spring design. Could someone clarify? -- DevSolar (talk) 05:54, 23 August 2012 (UTC)


 * This article is talking generally, but in the Panzer II it is referring specifically to that implementation on that vehicle. Not that either claim is backed in the articles by footnotes to the source. GraemeLeggett (talk) 06:58, 23 August 2012 (UTC)


 * I just wondered, because there is hardly a better comparison than having both type of suspensions in basically the same vehicle. Funny enough, when looking for sources, I realized that the German article claims not a Christie, but a torsion bar suspendion in the D/E models... something is surely amiss here. -- DevSolar (talk) 07:26, 23 August 2012 (UTC)

Usage
I notice the Merkava is listed, but can't find any support for the claim? BP OMowe (talk) 13:00, 21 April 2013 (UTC)

Buehlchit speed record
You Wiki people are hilarious. You demand "citations" yet reject "but I was actually there" evidence. To verify the utterly ludicrous claim that a Christie tank went 104 mph, you cite some baloney reference in a Popular Mechanics of the time. This was a magazine that was replete with breathless flying-car, floating-apartment-building, monster-this-and-that copy in those days, yet you accept it as proof of the fact that a tank went 104 mph. (The current 2014 tank speed record is 51 mph, by the way, set by a British Scorpion.)173.62.12.218 (talk) 23:27, 25 September 2014 (UTC)

That is how Wikipedia works. "I was there" is not acceptable. We can't just take peoples word for things. Plenty of people willing to make crap up. It must be published information. Everyone reading it (who is smart enough) realizes that doesn't make it necessarily true, but we can't just use "I was there" as proof for anything. Sure, that can be frustrating at times, but can you imagine how much worse it would be if people could just post any old "fact" by claiming they "saw it with their own two eyes"? (Not that it really stops them from doing it all the time). I'm not sure what the argument you are referring to is, but you are perhaps aware that the Christie suspension is designed so the tracks can be removed and the tank can drive on it's roadwheels only? This makes higher speeds possible than driving with tracks on. 104mph is dubious, but not impossible, and the 51mph of the Scorpion was undoubtedly made with tracks on. Although I am sure I've heard of M1 Abrams reaching higher speeds than 51mph...but perhaps that's not official? BTW, I've never seen Popular Mechanics claim that anyone is actually making flying cars or floating apartment buildings. They deal with people who talk about the possibility of creating some of these things. If they claimed the tank went 104mph, then likely that is how it was reported to them, and it's not the same to report something that allegedly happened than to report something that might someday happen. So stop being butthurt. .45Colt 19:07, 15 February 2015 (UTC)

Illustrations II
I agree with the guy at the top...that "schematic" is a good start, but it doesn't make it at all clear how the system actually works. Where are the pivot points to transfer the leverage? How do these so called "pipes" that the roadwheels are mounted on work? Do the pipes themselves move, or do they hold a shaft which transfers the vertical motion to the bellcrank shaft (and for that matter, the text describes something about the shaft connecting to the top of these "pipes", yet in the upper illustration, it appears that the shaft connects directly to the roadwheel. An animation would be great. Also real quick, I was curious why Christie designed this suspension so he could lay the coil springs horizontally, yet it says that the Russians used it with vertical springs in the T-35 and angled springs in the T-34...is that still truly a Christie suspension, and why did they not see it as important to utilize the fact that the springs could be mounted horizontally? I'm guessing it's because their tanks were bigger than the ones Christie was attempting to design, but it would be nice to have some clarification..45Colt 18:41, 15 February 2015 (UTC)


 * Let's just start all over again: Everything you've ever heard about Christie suspension is wrong.
 * Secondly, Christie was working in the late 1920s, at a time when suspension (tank or even car) was crude. Also metallurgy was crude and coil springs could only recently be forged. So it's wrong to compare Christie to Horstmann, Horstmann's symmetrical scissor or more modern suspensions and say (as is usual), "But why is Christie seen as advanced, it looks so crude?".  The point is that Christie was developing his suspension in a context of leaf springs and cantilevered bogies with minimal travel, fit only for low speeds.
 * Christie's design can be seen in his patent. (No idea why this doesn't seem to be in the article) The crucial aspects are:
 * Use of coil springs in compression, anchored to the chassis at one end
 * Independent suspension for each wheel station (no bogies to balance loads between two wheels, so all movement in this suspension turns into spring movement, unlike Horstmann)
 * Use of a second order lever (mostly second order, sometimes first with unequal lengths): this gives greater wheel travel, but increases spring load.
 * Two other aspects were considered important at the time, but hindsight shows that they had little effect on AFVs.
 * Use as a wheeled vehicle, without the tracks
 * Potential for drive through the suspension to the wheels (necessary if it's a non-tracked vehicle). This was facilitated on Christie suspension as the links were a constant length and constant distance from the pivot point (unlike a leaf-sprung bogie).
 * Christie suspension was an advance over those of the time, but it was surpassed during WWII. The principles were good, but it wasn't the only way to achieve them. Torsion bars were popular as a way to achieve springing for even heavier vehicles. Rocker bogies gave a more efficient suspension for rough ground, as the rocking action across a bogie avoids having to put all of the force into a spring.
 * Some things that Christie doesn't restrict:
 * Spring position. Christie built them inclined backwards from the pivot to allow longer springs in the same hull height, but the Soviets stuck them all over the place. It's just not a defining feature of the design.
 * Trailing or leading arms. Oddly, some designs went with leading arms, or see-saw pairs. Generally a downgrade of the trailing arm, but it could allow equipment to be rearranged.
 * The issue with coil springs is because of metallurgy. Forging a coil spring requires substantial strain, because of the need to coil them. They can't be made like this, and to take an applied load, without sophisticated metallurgy, mostly in their heat treatment after shaping. This wasn't possible for such large springs until WWI, mostly from research into making springs for artillery recuperators. Between the wars, just making the small coil springs for engine valves was a perennially unreliable process. A leaf spring, in contrast, requires little shaping from the rolling mill and barely any additional strain from its shaping, compared to the spring load. Andy Dingley (talk) 23:11, 15 February 2015 (UTC)

Untitled
Delete the schematic and check out Patent US 1836446 A for the real mode of action. A Christie suspension doesn't use a bell crank. The axles of a regular crank connect to the wheel respectively to the hull of the vehicle, the crank arm is seen as a lever, its center serving as a fulcrum to which the vertically mounted spring is attached. It was never intended to change the direction of motion, but to use the principle of the lever. Considering the schematic, the suspension of the bogies would interfere either with the sprockets or with the idlers. 22:41, 20 August 2016 (UTC)
 * What's a bellcrank in this sense? Do you claim that the suspension spring axis must always be at a near right angle to the trailing arm?  Do you claim that the spring pivot attachment to this lever must be in line between the suspension pivot and the wheel axis? Both of these were common forms of the Christie suspension and weren't, AFAIK, challenged to not be so. Christie's patent doesn't show this layout for the road wheels, but it does use a bellcrank and horizontal spring for the leading wheel, as Christie expected this to act sometimes as a roadwheel when crossing ditches.
 * I don't understand your use of the term "fulcrum" here either. "its center serving as a fulcrum " suggests a first order lever. Most Christie wheel stations were second order, with the fulcrum at one end and the spring in the middle (Discussed in my comment above). Only a few were first order levers. Andy Dingley (talk) 09:12, 26 September 2016 (UTC)

Polish tanks 10TP/14TP did not use Christie!
It is an urban legend that Poles made their own Christie. They did not. Use www.translate.ru to read http://vn-parabellum.narod.ru/pl/10tp.htm Actually USSR hastily provided a better bid and Christie did not sell the license to Poland but to USSR instead. So Poles had to come up with a suspension of their own design. The link above holds the schematics of it and it is nowhere near. This schematics is taken from Poland author J.Magnuski according to http://www.aviarmor.net/tww2/tanks/poland/10tp.htm ( see the links at left bottom after the photo ) 79.111.232.2 (talk) 20:11, 25 September 2016 (UTC)
 * Unless the comment above is correct. Indeed the very photo of destroyed T-34 in the article shows VERTICAL shafts, not horizontal. If the comment above is correct, then the no-becrancs schematics of 10TP might be Christie-like indeed. 79.111.232.2 (talk) 20:16, 25 September 2016 (UTC)


 * Why would these Polish designs not be considered as Christie types? Andy Dingley (talk) 09:13, 26 September 2016 (UTC)

Swivelling upper spring seats and Polish innovation?
Christie's patent, and the first examples built, had the upper end of the compression springs resting on a screwed seat. This (in Christie's design) could be screwed up and down to balance out the wheel load. The difficulty is that some geometries also caused the lower spring seat to move transversely to the spring axis (forwards and backwards) as the suspension moved. This rocked the spring on its seat and when a coilover arrangement had been used with a telescopic hydraulic shock absorber within the spring body, it placed bending forces onto this shock absorber, damaging its piston rod and seal.

The fix was to pivot the upper spring seat. AIUI, this was a Polish innovation, outside of Christie's development.

Can anyone expand on this? Andy Dingley (talk) 09:28, 26 September 2016 (UTC)

Steel-rimmed wheels & discomfort
I have been editing out reference to steel-rimmed wheels because the Christie-built vehicles had solid rubber tires. All the BTs had solid-rubber tires. Every British cruiser I've seen had solid-rubber tires also, although I am certainly willing to be corrected on that point. Some T-34s, mostly those built at STZ and Factory 183, had steel rims. But that content doesn't seem to fit in this section of the article, which is dealing with the original Christies of the 1920s and 1930s.

The other thing is that the US officers who tested some of the early Christies commented over and over how much *better* the ride was than anything else they'd ever experienced. By the standards of the 20s and 30s it seems the Christies were quite good.

Maybe we should create a section to describe some of these later developments and testing, but, I really don't see how it belongs there.

Regards,

DMorpheus2 (talk) 20:08, 11 October 2016 (UTC)


 * Three times now you have broken this article and made it read, "Christie used large rubber-rimmed road wheels, with no return rollers for the tracks, which gave an uncomfortable ride."  This is sloppy editing and simply wrong. No doubt the steel rims did make the ride harsher, but it was not the lack of return rollers that did! Nor even the rubber rims.
 * Please fix your edits.
 * As to the rest, then I don't see any merit to your claim "this refers to Christie prototypes, not e.g. the T-34". Obviously it doesn't. If you think that a run-on sentence is making it look that way, then the fix for that is to copyedit the para however you wish, not to delete an accurate observation about the wartime ersatz production. Andy Dingley (talk) 20:16, 11 October 2016 (UTC)


 * Content about wartime production does not belong in the same section as content about the 1930s/20s prototypes. I thought I made that clear enough in my edit comments but obviously I was wrong. Thats why I added this section to talk.
 * Let us avoid the term 'ersatz' which is unnecessary German and therefore unnecessarily confusing. We're not writing about German vehicles. As far as I know this would only refer to Soviet vehicles, and even then, only to those T-34s produced at the factories (183 and STZ AFAIK) that used steel rims. Might not be a terrible idea to break out all production based on Christie's ideas (BTs, T-34, British cruisers....) from his own vehicles so as to make these distinctions clearer.
 * I am aware of users at the time who thought the ride was smoother than competing designs. So the whole thing is dubious anyway.
 * Regards, DMorpheus2 (talk) 13:18, 12 October 2016 (UTC)
 * Have you even read how you've left the article? It's inaccurate nonsense. Andy Dingley (talk) 15:24, 12 October 2016 (UTC)


 * I don't believe it in inaccurate but kindly point out exactly what you believe is inaccurate. AFAIK the only steel-rimmed wheels ever used on a Christie-type tank were the T-34 variants I've mentioned already. If you know of others I'd truly love to hear about it. A little civility goes a long way. DMorpheus2 (talk) 15:43, 12 October 2016 (UTC)


 * Here is the source on US Army officers saying the Christies gave a better ride than other tanks on which they had experience: http://tankarchives.blogspot.com/2013/07/christie-tank-trials-and-foreign.html  — Preceding unsigned comment added by DMorpheus2 (talk • contribs) 15:45, 12 October 2016 (UTC)


 * And another: http://cgsc.contentdm.oclc.org/cdm/singleitem/collection/p4013coll11/id/2071/rec/7
 * "The Christie suspension which appeared for the first time in 1919 merits special consideration. For the first time a relatively stable gun platform was provided along with a smoother riding vehicle." DMorpheus2 (talk) 15:49, 12 October 2016 (UTC)

Here's the current paragraph: Another feature of Christie's designs was the "convertible" drive: the ability to remove the tracks for road travel, allowing for higher speeds and better range, and reducing wear on the fragile caterpillar track systems of the 1930s. In one public test 1931 in Linden, NJ, Army officials clocked a Christie M1931 tank attaining 104 mph (167 km/h), making it the fastest tank in the world: a record many believe it still holds.[3] To allow this, Christie used large rubber-rimmed road wheels, with no return rollers for the tracks, which gave an uncomfortable ride. As with many track designs with center guide teeth, dual wheels were used, allowing the guide teeth to run between them. By 1939, the Soviets found that the BT tank's convertible drive was an unnecessary complication which occupied valuable space in the tank, and the feature was dropped in the T-34.

Here's my suggested edit: "Another feature of Christie's designs was the "convertible" drive: the ability to remove the tracks for road travel, allowing for higher speeds and better range, and reducing wear on the fragile caterpillar track systems of the 1930s. To allow this, Christie used large rubber-rimmed road wheels, with no return rollers for the tracks. A chain drive from the drive sprocket was engaged to the last road wheel to propel the tank, and the front set of road wheels was steerable. Although track removal could be accomplished in about 30 minutes, both the British and the Red Army found that the convertible drive was an unnecessary complication which occupied valuable space in the tank, and neither the T-34 nor the British cruiser tanks had convertible drive."

The speed bit can be moved elsewhere.


 * BT Fast Tank: The Red Army's Cavalry Tank 1931-45" just released, ISBN 978-1-4728-1065-6, p.6, the Chrisite Model 1928 gave "...a particularly smooth ride..." compared to other tanks of the era that generally had leaf-spring suspension. DMorpheus2 (talk) 12:09, 14 October 2016 (UTC)

"Schematic"
The "schematic" of the Christie suspension seems pretty worthless, since it's obviously missing at least one very crucial pivot point. right now it just shows a coil spring connected to a wheel via two articulated bars, but moving that wheel up and down isn't going to have any effect whatsoever on the coil spring, it's just going to make the pivots in the red bars flex slightly. The only way I can see this working is if the vertical bar had a pivot in the middle where it mounted to the tank which turned it into the bellcrank lever, probably around 1/3rd or 1/4th of its length from the lower joint. Thus when the wheel moves up, this causes it to pull on the horizontal rod, which pulls on the lower end of the vertical rod, which rotates on its pivot, acting as a lever, pushing "down" on the coil (i.e. sideways). This is not clear at all from the picture or description. I only say that because it's the only way I can imagine that the mechanical stuff in that picture COULD work. I hate to think of the people who are less able to visualize mechanics trying to figure that out. I see someone else actually mentioned this already, although I don't see any actual answer to their question. What does the Hoffman system have to do with it? I just want the illustration clarified. I also think he/she makes a good point, why DID the Russians use vertical springs and a Christie suspension, while the article says that part of the point was to allow the use of horizontal springs. If you're going to use vertical springs anyway, why bother with the bellcrank nonsense? I'm assuming it's because it allows you to use a shorter spring for a given level of articulation, no matter what angle the spring is at. But then again, how do you use a bellcrank to link a vertical-travel roadwheel to a vertical-travel spring? Those are vertical coil springs in the photo of the blown-apart T-34, aren't they? AnnaGoFast (talk) 03:30, 22 January 2018 (UTC)


 * Fixed that I guess . Alexpl (talk) 21:23, 7 February 2019 (UTC)

Comet tank
BTW, why is the Comet listed at the bottom as being one of the tanks with Christis suspension. I wouldn't deny it, except for the fact the article seems to say that the lack of return rollers is a prerequisite for Christie suspensions, and the Comet tank quiet clearly has return rollers. Other than that I see nothing about it that would indicate that it's not a Christie suspension. AnnaGoFast (talk) 03:36, 22 January 2018 (UTC)
 * Read some of the talk page comments.
 * What is a "Christie suspension"? One built by Christie?  One built exactly as Christie did?  Or one continuing the key principles of Christie's design?
 * Return rollers are an option for Christie suspension, as they can be omitted for a rear-drive slack track design (as the Soviets favoured). However using return rollers doesn't stop something being a Christie design. Andy Dingley (talk) 11:17, 22 January 2018 (UTC)

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