{"id":89031,"date":"2023-01-20T07:46:14","date_gmt":"2023-01-20T15:46:14","guid":{"rendered":"https:\/\/www.racingjunk.com\/news\/?p=89031"},"modified":"2023-01-20T07:50:18","modified_gmt":"2023-01-20T15:50:18","slug":"what-you-need-to-know-about-street-strip-driveshafts-part-2","status":"publish","type":"post","link":"https:\/\/www.racingjunk.com\/news\/what-you-need-to-know-about-street-strip-driveshafts-part-2\/","title":{"rendered":"What You Need To Know About Street & Strip Driveshafts Part 2"},"content":{"rendered":"\r\n

\"Mark<\/a><\/span><\/p>\r\n

Part 2 of Wayne Scraba’s series on street and strip driveshafts focuses on balance and universal joints.<\/em><\/h2>\r\n

In our last issue<\/a> we introduced you to a wide range of driveshafts from Mark Williams Enterprises<\/a> . If you point your browser back to the first article in the series, you\u2019ll note M-W manufactures driveshafts from mild steel, chrome moly steel, 6061 aluminum, 7075 aluminum and carbon fiber. Each has its own different characteristic and price points. Some take more power to spin than others. But all have two things in common: They need to be balanced and they need some sort of universal joint in order to function.

When it comes to driveshafts, universal joints are critical. No surprise we\u2019re sure. You\u2019ll note we\u2019ve been zooming in on Spicer \u201clubed for life\u201d, non-greaseable u-joints. There\u2019s good reason for that. According to Mark Williams:

\u201cMost driveshafts used in drag racing employ 1350-series U-joints, although for high horsepower, Pro-Mod applications 1480-series joints are starting to be introduced for specific transmission\/rear axle combinations. There are also differences in U-joint construction, ranging from stock Spicer units with zerks to solid non-internal greasing units.\u201d

If you have ever had the opportunity to see a cross section of a universal joint with a zerk fitting and an internal grease passage, you\u2019ll quickly realize why solid \u201clubed for life\u201d universal are superior: They\u2019re simply much stronger. The hollow internal grease pathway weakens \u201clubeable\u201d universal joints by a considerable margin.

It\u2019s interesting to learn that a large chunk of driveshaft failures is caused by universal joint failure, especially in heavier cars. Many high performance vintage cars were originally fitted with Spicer 1310-series universal joints. Here the u-joint cups measure 1.062-inches in diameter with a width of 3.219-inches. In comparison, a Spicer 1350 universal joint has a cup diameter of 1.188-inches and a width of 3.625-inches. Meanwhile, the honking Spicer 1480 series universal joint commonly found under Pro Mod cars has a cup diameter of 1.375-inches and an overall width of 4.180-inches. A 1350 u-joint is approximately 50% stronger than a conventional 1310 while a 1480 u-joint is 40% stronger than a 1350.

On a similar note, OEM-style U-bolts are also suspect in severe duty applications. For specific applications, M-W offers a billet steel cap assembly that can handle up to 500 foot lbs. additional torque.

Fair enough, but how can one quantify strength figures on a driveshaft? M-W developed an immense Torsional Testing Device that can exert up to 20,000 lbs. of torque on the driveshaft, and is used for a variety of purposes, including verifying the bonding strength of all M-W \u201cAccu-Bond\u201d driveshafts and conducting tests for SFI to determine compliance with SFI 43.1 Specs.

There\u2019s more, too. According to Williams, \u201cProper phasing of the U-joints to the shaft is critical, and for drag racing applications a \u201c0\u201d phase setup (front and rear U-joints are in the exact same position) has proven to be the best.

\u201cBalance is also important, and it can have an effect upon performance because the laws of physics tells us additional radial power is required to turn an eccentric shaft, Basically, if the driveshaft is perfectly balanced the car will put more power to the ground.

\u201cTo assure this, M-W has a sophisticated computer-controlled balancer that can spin test to 10,000 RPM and is used to replicate actual operating conditions. The shafts are balanced to G30 specifications.

\u201cThere are also factors, such as transmission and rear end yokes, to consider. But in the end it\u2019s best to put your trust in a reputable manufacturer rather than rely on warmed-over stock components.\u201d

So how important is driveshaft weight? In a nutshell: Very! The weight of the driveshaft has a direct effect upon the performance of the car. Not only will a heavier driveshaft add to the weight that rolls down the track, it will also take more power to spin a heavier driveshaft. Consider this info from Williams:

\u201cFor the sake of comparison, we will use 45-inch center-to-center, 3.5-inch o.d. driveshaft with a M-W 39004 Turbo 400 trans yoke. Steel, of course, is heavier than aluminum or carbon fiber. A 3.5-inch o.d. shaft made of chrome moly tips the scales at 20.6 pounds. Aluminum is by far more popular, and M-W\u2019s exclusive 7075 alloy driveshafts are 13.7 pounds. A 3.5-inch o.d. 7075 shaft weighs about 33% less than an equal size chrome moly shaft. This translates to 33% less power needed to accelerate the driveshaft to operating RPM, and the faster the driveshaft spins the more power that is saved.\u201d

Does this really have an effect in the real world? Decades ago, this writer tested driveshafts for another publication. The car in question was an extremely reliable, well-sorted and consistent Stage 1 Buick Stock Eliminator car. We devised a simple plan where, on a quiet test and tune day, we\u2019d baseline the car with a steel driveshaft, remove and replace the shaft with an aluminum example, run the car and then swap back to the steel driveshaft and run the car once more. Essentially, this was a common \u201cA-B-A\u201d test pattern. We used a known weather station to keep track of conditions. The simple driveshaft swap picked the car up from 0.035 to 0.078-seconds. And those are the uncorrected numbers. As the test progressed, the weather changed (even in a total time span of just 53 minutes). Using correction factors, the improvements were still impressive (a spread of 0.039 to 0.059). Lots of racers would sell their sisters for a gain of half a tenth. More important were the incremental times. 60′ times improved. So did 330′ times, 660′ times and so on. Following the computer evaluation, we found that the true improvements all came during the first 3\/4 of the pass. Then the car slowed down a bit. Our hypothesis? The Buick doesn’t really like the 4.30 gear. It really needs a 3.90 gear or a 4.10 ratio coupled with a set of “tall” 30″ radial slicks. In the end, we concluded that reducing driveshaft weight consistently decreased elapsed times.

Two considerations here are the aluminum shaft wasn\u2019t exactly legal for a Stock Eliminator car (the Buick wasn\u2019t originally produced with an aluminum driveshaft), plus the shaft in question was a metal matrix aluminum shaft.

Metal matrix composite (MMC) 6061 aluminum was a revised alloy. It contained a certain amount of silicon carbide particulates that were said to increase the strength of the alloy. The shafts built with MMC material were typically thin wall (in the range of 0.110-inches \u2013 the same as an M-W 7075 alloy example). The reason metal matrix aluminum driveshafts aren\u2019t common today (basically non-existent) is because the material wasn\u2019t consistent. You could get a great weld on one shaft and the next it would be horrible. Or you\u2019d great weld on one yoke and on the other, the weld would be not so great, even using sophisticated automatic welding machinery.

The point of repeating the whole test exercise here is, a lightweight driveshaft (whether it is 6061 aluminum, 7075 aluminum or Carbon Fiber) will improve the performance of your car.

We\u2019ll end part 2 here, but next time around, we\u2019ll conclude out look at high performance and race driveshafts with a look at universal joint angles and critical speed. We\u2019ll also share Mark Williams\u2019 advice on how to measure for a driveshaft. There\u2019s more than you might imagine folks. Watch for it. Meanwhile, check out the accompanying driveshaft photos:<\/p>\r\n

 <\/p>\r\n

\"\"<\/a>
This particular shaft is fitted with huge Spicer 1350 universal joints. Note the epoxy used on the retainer. The reason for this is to ensure the retainer doesn\u2019t back out at high speed.<\/figcaption><\/figure>\r\n
\"\"<\/a>
Note the yoke. Williams uses 4130 yokes on 4130 chrome moly shafts and they use high strength 7075 forged (and machined) yokes on 7075 driveshafts along with Carbon Fiber driveshafts.<\/figcaption><\/figure>\r\n
\"\"<\/a>
In the text we noted Williams has an in-house driveshaft testing machine that can apply 20,000 foot-pounds of torque to a driveshaft. The Accu Bond process M-W uses in their 7075 aluminum and Carbon Fiber driveshafts is so strong, a solid 1350 universal joint will fail before any part of the shaft.<\/figcaption><\/figure>\r\n
\"\"<\/a>
The same epoxy is used at the rear of the driveshaft. M-W offers shafts with these large 1350 universal joints along with even larger 1480 universal joints. The text offers more info on u-joint sizes<\/figcaption><\/figure>\r\n\r\n\r\n","protected":false},"excerpt":{"rendered":"

Part 2 of Wayne Scraba’s series on street and strip driveshafts focuses on balance and universal joints.<\/p>\n<\/div>","protected":false},"author":20,"featured_media":89229,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"gallery","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[5011,11,3470,5012],"tags":[9493,4321,321],"class_list":["post-89031","post","type-post","status-publish","format-gallery","has-post-thumbnail","hentry","category-chassis-suspension","category-how-tos","category-news","category-transmission-clutch","tag-driveshafts","tag-mark-williams","tag-wayne-scraba","post_format-post-format-gallery"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/www.racingjunk.com\/news\/wp-content\/uploads\/2023\/01\/Driveshaft-6-min-scaled.jpg","jetpack_shortlink":"https:\/\/wp.me\/p42YSK-n9Z","jetpack_sharing_enabled":true,"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/89031","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/users\/20"}],"replies":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/comments?post=89031"}],"version-history":[{"count":5,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/89031\/revisions"}],"predecessor-version":[{"id":89234,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/posts\/89031\/revisions\/89234"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/media\/89229"}],"wp:attachment":[{"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/media?parent=89031"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/categories?post=89031"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.racingjunk.com\/news\/wp-json\/wp\/v2\/tags?post=89031"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}