Talk:Drum brake

Cleanup
This article repeats itself a lot. The decription of the self-adjustment capability and the use of drums for parking brakes is mentioned in the article twice. 81.178.235.56 16:39, 19 January 2007 (UTC)

Asbestos regulation by who?
FTA: "The Federal government began to regulate asbestos production" - which federal government does this refer to? The U.S. government? 87.194.198.122 (talk) 12:40, 13 January 2008 (UTC)

needs better illustrations
or possibly an animation. --Rajah (talk) 23:07, 1 March 2010 (UTC)

Animation
http://webcache.googleusercontent.com/search?q=cache:http://auto.howstuffworks.com/auto-parts/brakes/brake-types/drum-brake1.htm this is a web link to a good site with an animation —Preceding unsigned comment added by 122.148.117.37 (talk) 05:26, 10 July 2010 (UTC)

Brake drum versus Drum brake.
They are two different things. GEEZ. User:Deathgleaner 23:27, 15 August 2010 (UTC)

Bicycle Drum Brakes!
Bicycles use drum brakes, too -- usually as an auxilary on tandems, in my experience. Should include other uses too (aircraft??), if applicable. —Preceding unsigned comment added by 96.225.231.50 (talk) 16:54, 29 December 2010 (UTC)

Drums on Parking Brakes
I am unsure about the statement that the "vast majority" of cars use screw-style disc brake parking brakes. — Preceding unsigned comment added by 74.5.209.206 (talk) 20:52, 5 August 2014 (UTC)


 * I dialed it back to "many". If someone has stats, they can assert something more specific. — ¾-10 01:28, 6 August 2014 (UTC)

How-to advice
These two paragraphs in the "Safety" section are how-to advice:

It doesn't help to take "You should use a vacuum enclosure and you should make sure it fits around the entire brake" and rewriting it in passive voice "It is recommended that enclosure systems should fit around the entire brake." When you simply imply agency instead of saying it, it doesn't change the fact that you're giving advice, exhorting the reader to do things. WP:NOTHOWTO gets to the heart of this:

"Describing to the reader how people or things use or do something is encyclopedic; instructing the reader in the imperative mood about how to use or do something is not."

The NIOSH sources cited are not describing how workers carry out brake maintenance. Have you ever seen one of these vacuum enclosures around the wheel of your car?

They are describing how the agency thinks they should do it. It would be a welcome, encyclopedic addition to this article if we did describe how actual brake maintenance is done, particularly in light of the significant gulf between how it's actually done and how NIOSH thinks it ought to be done. It would be encyclopedic to tell the reader what percentage of shops use zero asbestos mitigation, what percent use water methods, and how many use the mythical vacuum enclose.

This raises neutrality issues as well. It is misleading to suggest that NIOSH's point of view is the last word on what the best practices are. At the opposite extreme, the Automotive Aftermarket Industry Association and the Automotive Service Association (ASA) beg to differ with NIOSH on this. At first glance, it appears that the ASA lobbied the EPA to water down the stuff about the giant vacuum bag, and instead recommend the much cheaper "wet wipe" method which ended up in the final EPA brochure. Even then, I'm not sure that verifiably describes "to the reader how people or things use or do something", as required by the NOTHOWTO policy.This is a worthy topic for encyclopedic coverage, and we could expand the topic of brake maintenance to an entire article, but we have to seek out independent sources, and when we cite POV sources like NIOSH, we have to balance that with those that disagree. As WP:NPOV says, "Articles must not take sides, but should explain the sides." The first step in explaining the sides is being aware that the sides exist. --Dennis Bratland (talk) 16:56, 16 July 2016 (UTC)


 * Another source recounting some of the controversy around asbestos in the auto industry. For example, "The prevailing industry position is that asbestos exposure to auto mechanics is negligible, as stated by Michael Palese, a spokesman for Daimler-Chrysler Corp., 'There is no proof of asbestos in brakes ever harming those working on or around them.'" Another reason why asbestos mitigation is not widely practiced: "asbestos has been all but eliminated" so it's somewhat moot. --Dennis Bratland (talk) 17:29, 16 July 2016 (UTC)
 * Another point: "A significant increase in imports of automobile brakes containing asbestos over the past decade is raising renewed concerns for the health of the nation's auto mechanics... Most U.S. automakers stopped installing brakes with asbestos in the 1990s" --Dennis Bratland (talk) 17:44, 16 July 2016 (UTC)
 * Do brake vacuums even exist? As a basic sanity check, I wanted to see if you can even buy a brake vacuum. Apparently Nilfisk-Advance did make one in the past, based on this auction of a surplus unit. But they no longer make any such automotive equipment, and I can't find any evidence that anyone else does either. The UK does not even mention such equipment, but instead says water is a good idea. --Dennis Bratland (talk) 19:15, 16 July 2016 (UTC)
 * Agreed. Thank you for researching it.  An expert advises me that: (1) Asbestos is rare in brakes asbestos is still used now. Ceramics are used more. (2) It was normal to use a "wet method", such as a wet brush, to minimize dust. (3) Vacuum hoses, to safely suck away the dust, were rare, and enclosures are/were never used in practice. (4) "asbestos shoes" aren't use by car people and maybe never work; looking on the Web, they exist and are for sale but not for car work.  Possibly we can abbreviate this part of the safety discussion to something like "When asbestos was common, there was a danger of its dust getting into people's lungs.  Wet brushes and aerosol sprays were commonly used to reduce dust.  Safety regulators recommended the use of vacuum hoses or enclosures to suck away the dust,[footnotes] but these were rarely used."  We can add whether there's evidence that workers were harmed by asbestos from brakes, if we have a solid assertion about that.  The quote from Palese looks okay to me, but is there also data?  I will study your sources and maybe make an edit.  -- econterms (talk) 02:57, 18 July 2016 (UTC)


 * Here is a reliable source http://www.news.com.au/finance/business/manufacturing/toyota-has-issued-a-warning-about-thousands-of-counterfeit-brake-pads-containing-deadly-asbestos/news-story/b367ae352c742f7da14a02967b49fd3e, that states that Mechanics are over-represented in asbestos poisoning because it was legal to use in brake systems for decades, it also answers other issues being raised, there are plenty more Australian sources about asbestos use.. Gnangarra 23:54, 18 July 2016 (UTC)
 * That is consistent with the Baltimore Sun story that asbestos was all but gone, then saw a resurgence in imported brake (and clutch) pads. The unanswered question is whether the practice where "Mechanics would use an air hose to clean the brake components when fitting new pads, and the whole workshop would fill with asbestos dust" was the primary cause of illness. That method seems almost perversely deigned to ensure maximum dust exposure. Given how mechanics are typically bathed in so many other carcinogens, you'd need to identify a correlation with brake maintenance specifically, and tease out differences in illness with different safety practices before you'd have definitive proof (hence the DaimlerChrysler denial), though the asbestos cause is obvious fro a common sense point of view.NIOSH seems to base their thinking in the idea that there is no safe level of asbestos exposure, and therefore a system using an enclosure with HEPA vacuum that prevents any chance of inhaling dust must be used, without seeming to understand at all how impractical that is. The UK seems to have taken the approach that if you can just avoid deliberately creating a dust cloud, and instead trap the particles with water, the level of risk is brought down to a reasonable level. The US OSHA and EPA similarly ignored NIOSH's position and went with water and wet rags. The real problem was that eliminating asbestos at the source was successful, then fell completely apart when manufacturers with extensive resources and no oversight deliberately skirted asbestos bans.This issue is as much about disc brakes as drums, and focusing on this article can create the false impression that asbestos risk is gone since drum brakes are disappearing. And then there's clutches. And the dispute by the Union of Concered Scientists, and the other dispute by the car industry representatives. So where should we cover this issue?
 * Car repair (redirects to Breakdown (vehicle))
 * Automobile repair (redirects to Auto mechanic )
 * Brake
 * Brake maintenance
 * --Dennis Bratland (talk) 00:26, 19 July 2016 (UTC)


 * Well actually in Australia the standard is that there is no safe level of exposure to asbestos as well, so its not only NIOSH.  then there is also Wittenoom experience. The issue of correlation is causal is that Mesothelioma is consider to be solely asbestos exposure. Gnangarra 02:03, 19 July 2016 (UTC)
 * I understand that Wikipedia should not provide how-to advice. I do think though that articles should at least have some detail on proper procedures; in this case, proper brake-cleaning procedures. It is a fine line and I may sometimes get it wrong, so I appreciate edits. Additionally, I absolutely agree sources in addition to NIOSH-published research should be used. NIOSH is far from the only organization in the safety business, and the neutral point of view policy indeed requires giving due weight to multiple viewpoints on a subject if they exist. James Hare (NIOSH) (talk) 13:31, 19 July 2016 (UTC)

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Errors in illustration.
The illustration 800px-Tipologia_tamburo.svg.png is erroneous.

The three drawings in the bottom row are incorrect. Consider the link at the bottom of the uni-servo example. That link can transmit a force in compression only longitudinally between its pivots. At the left-hand pivot, the force can be described as two vectors, one pointing circumferentially clockwise and the other radially outward. Therefore, there must be an outward force on the bottom end of the leading shoe. The forces at the right-hand pivot must mirror those at the left-hand end -- equal and opposite action and reaction. The drag at the bottom of the right-hand shoe will be greater than at the bottom of the left-hand shoe, as the right-hand shoe has become a second leading shoe.

The drag depends on the location of the pivots in the floating link. I'd suppose that with a carefully chosen geometry, both shoes could have the same drag. That might require that the pivots be at different positions on the two shoes. This brake will work poorly in reverse.

The duo-servo example is effectively identical to the servo example for forward braking because the trailing brake shoe will butt up against the pin at the top. This is mirrored for braking in reverse.

The duo-duplex example is incorrect because no stop is shown for either brake shoe.

I have a revised version of the drawing at https://sheldonbrown.com/drum-brakes.html also showing cam actuation, which is usual with bicycle brakes, older motorcycle brakes and air brakes on large trucks, but leaving off the three servo examples, which are irrelevant to my topic and which I don't want to take the trouble to revise. Someone else might do that. Jsallen1 (talk) 13:55, 26 September 2018 (UTC)

Methyl Chloroform increases reaction time?
(In the Safety section) I found it odd that the CDC claims 1,1,1-trichloroethane increases reaction time, despite all the other adverse effects on the central nervous system. This is likely a typo and they meant to write "decreases reaction time." This study, https://www.jstor.org/stable/44376353?seq=1#page_scan_tab_contents, claims reaction time was impaired after exposure, further suggesting it was simply a typo. — Preceding unsigned comment added by 96.38.27.10 (talk) 19:10, 5 October 2018 (UTC)