Cycle News - Archive Issues - 1990's

WORKBENCH NEW VIDEO RELEASES By Brian Catterso n Now Available Throug h Cycle News Action Theater Springs: Progressive vs, dual-rate ast week in Workbench we discussed spring basics length, coi l distance and wire diameter. This week , we'll look at the differences between progressively wound and dual-rate springs. The one thing both progressively wound and dual-rate springs have in co mmo n is their goal: What each attempts to achieve is progressive suspension action - that is, soft initial movement to absorb small bumps which becomes increasingly stiffer as the suspension nears full compression .Io r bigger bu mps. However, the manner in which each type goes about achieving its goal is completely different. Simply sta ted, a progressi vely wound spring varies its ra te th roughout its length , whi le a dual -rate spring is ei ther a single spri ng wound at different rates at either end or a pair of straigh t-rate spri ngs with different coil distances and a spacer between th em; typically, a short, stiff spring is paired with a longer soft on e. There is another way to create a progressive spring - by varying the wire diameter from one end to the other. However, this is very uncommon, a nd far more costly to manufacture. A popular misconception is that a progressive or dual-rate spring will compress its softer section before its stirrer section. This is simply not true. What actually happens is the spring compresses as a whole, and then , as the portion with the smaller coil dista nce (also referred to as pitch) becomes coil-bound, the remaining stiffer section (with the larger coi l distance) will take up the force. Thus, in th e case of a tru e pro gressively wound spring, if you were to start wit h a give n numb er of coils, you wo uld gradua lly lose them o ne by one as the spri ng compresse d. O ne clari fication fro m last week's colum n: Coil distance does not -b y and of itsel£ control the ra te - it's m ore a fun ction of th e spring len gth , which is the real controlling factor. If you recall last week's example of leverage - the longer a p iece of metal, the easier it is to bend - you' ll real ize that the more coils you have in a given distance, the longer the metal composing the spring, thus th e softer the spring rate. As Gil Vailla ncourt of Works Performance put it: "Essentially, a spring is no t h i n g more than a torsion bar. " Ano ther factor involved in determin ing a spring's rate is the coil diameter. Generally speaking, the smaller the diameter, the sti rrer the spring. Of course, to a certain extent th is is governed by th e di am eter of the fork tube or shock bod y. O ne fin al" factor in determining spring rate is th e tensile strength of th e materi al bein g used. Simply put, th e.stronger th e metal, the stiffer the spn ng. L Workbench is a weekly column dealing with motorcycle maintenance, performance and equipment. Have something that Workbench can address? Drop a line to Workbench, Cycle News, P.O. Box 498, Long Beach, CA 90801-6498. 1990 AM! Grand Nat'l. Championship/CAMEL Pro Series VideOs. i • Just released by Despain Associatesl 1990 Ascot (Spring) Half-Mile (#200) This video is the essen ce of din-track rac ing ; two of the best in the bus iness duel for 20 laps and decide it all in a one -lap das h to th e flag. 1990 San Jose (Spring) M ile (#201 ) Parker takes the clear w in over an unbelievable race in the pack for second between 8 r iders . 1990 Springfield (Spring) mile (# 20 2) Scotty Parker breaks away fr om a 7 -r ider batt le to score an impressive w in . Slow-motion replay of rook ie Andie Huff's amazing end-over-end crash, Morehead taps Keit h Day at 130 mph • . and tangles w ith Ingram in the last-lap battle for the runner-up spot . Retail Price on these releases incl udes sh ipping . $28.95 each , By Despain Associates 1990 Louisville Half-Mile (#203) Chris Carr shatters the record for 20 laps on the rugged limestone oval. Slowmotion footage of crashes by Atherton and Ingram. and inside the pits as the Camel Pro riders prepare for combat. To Order Videos, Use The Video Order Blank Elsewhere In This Issue Of Cycle N~s ~·rI~S~ S~SaLe! /1"9' I gt4 tht«- Sept. 14t g'atu aftItaItd eU ~ ~ 40S ~ Shop Hours : Tues- Frl 10am-6pm Saturday 10am-3pm 660 W. 16th St ;. long Beath. (213) 435-6551 C~ 90113 r------------------------------------------------~ I I I Attention Subscribers, I I I I When you move ... I I i.For FASTEST service attach old mailing label in the space provided. If mailing label is not available. print your name and address in this box. Please allow 3 weeks for change 10lake effect. I I I I I I I I I I I I I I I I I I I I L I . ~_~ 13

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