GPL: How were bump rubbers really used?

>So is this the way bump ***s really work? Or is my new >setup philosophy completely flawed? You've got the general idea; longer bump ***s have a smoother transition from the spring-only rate to the spring+*** rate, with the beginning of the transition happening earlier in the travel. So stick with it; you may well be on to something. In fact, during the 80's, it wasn't uncommon to have the entire shock shaft filled with bump ***s, for a very progressive spring rate. Don't know about earlier or current practices. Too bad we don't know more about GPL's suspension geometry or the ***s' durometer(s). I'd be curious to know if the full-length 2.5 inch BR's would fill the shock shaft. BTW, if you're a glutton for this stuff, you can find some earlier, extended musings of mine on the subject by searching my posts via dejanews.com for "low riding and bump rubbing". Cheers, Steve B. remove "edy" from address for email

>Does anyone know how bump ***s really used back in '67? In those days we saved them for very special dates, usually older girls in college. FWIW, my wife has requested that I find more--and wishes I weren't as fast as I am while hot-lapping. Eric Ziegler

It would be interesting to know what the rest of your set-up is so I can try it out. I only seem to noticeably hit then bump ***s at the Nurburgring, just before I disappear into the scenery. Steve

Quoted text (11 lines)

>Thanks for the info, but in GPL, you definitely can hit the >bump ***s at 3.5" rideheight and 1" bump ***s. (maybe >it was 3.25", don't remember exactly) There was a >quite noticable difference when I switched to 4". I tested >it and retested it. I really think somewhere around 3.5 to >4 is the minimum for keeping the Lotus completely off the >bump ***s. > -A >**** Posted from RemarQ - http://www.remarq.com - Discussions Start Here

(tm) ****

Quoted text (14 lines)

>>So is this the way bump ***s really work? Or is my new >>setup philosophy completely flawed? >You've got the general idea; longer bump ***s have a smoother transition >from the spring-only rate to the spring+*** rate, with the beginning of the >transition happening earlier in the travel. So stick with it; you may well be >on to something. In fact, during the 80's, it wasn't uncommon to have the >entire shock shaft filled with bump ***s, for a very progressive spring >rate. Don't know about earlier or current practices. Too bad we don't know >more about GPL's suspension geometry or the ***s' durometer(s). I'd be >curious to know if the full-length 2.5 inch BR's would fill the shock shaft. >BTW, if you're a glutton for this stuff, you can find some earlier, extended >musings of mine on the subject by searching my posts via dejanews.com for "low >riding and bump rubbing".

I know that now days there are bump ***s with different conical profiles so that ***s themselves have a progressive rate. Anyone know if these existed back in the late 60's? -- | "Instead of letting the moon be the Bill Mette | gateway to our future, we have let Enteract, Chicago | it become a brief chapter in our

Quoted text (9 lines)

>*** is incompressible but deformable...interesting distinction, but the relevant point is it does act as a spring whose rate is affected by it's shape. >And more important here, is that variation in spring rate modeled in GPL? >I agree hysteresis is probably not modeled nor should it be unless there is a choice of tires. >Mark, you a tire engineer? If so, I have a ton of questions. :-) Tire technology has always facinated me as the black art of racing. >Marty

'fraid I am not a tyre engineer. In fact, to be honest, I all but exhausted my fund of knowledge in that one message! Does anybody else find it curious that Papyrus never give us any informed statements about what is and is not included in the GPL physics model? I would like to think that it is because they think it unwise to remove any layers of the "mystique" of the simulation. Enjoyment of a good sim. is, in my view, all about the "suspension of disbelief" (like the cinema), and the more insight you gain into the workings of the software, the harder it is to become immersed in the virtual experience. On one level, I am keenly interested in how it is all achieved, but on another, I want to be fooled into believing that I am racing against real world factors and human intelligence. Come to think of it, I struggle with the same trade-off with films too. Mark Croasdale

Well, that's a very good point. But I don't mean to beat GPL's physics model to death, I just find this sort of thing interesting way beyond what goes on in GPL. My new setups are working out great, so I'm gonna stick with my new techniques realistic or no. Too bad you say exhausted what you know on the previous posts, cuz I have some questions for you! Do you know when these progressive rate bump ***s were developed exactly? I'm guessing the development of downforce must have made them much more desirable. And what the heck do these things look like anyway? The GPL book describes them as "cones" as I recall. Are they solid? Hollow? Hope you have an answer! Thanks for what you've contributed so far, anyway. -A **** Posted from RemarQ - http://www.remarq.com - Discussions Start Here (tm) ****

> Do you know when these progressive rate bump ***s were > developed exactly? I'm guessing the development of > downforce must have made them much more desirable. Don't know the exact history, but I wouldn't be surprised if the racers took the idea from passenger cars (which have had *** bumpers to isolate the chassis from outsized bumps for a long time). This business of "racing improving the breed" can work the other way too... First organized bump ***s I saw came with Koni(?) shocks (dampers) in the late 1960's (seen in the garage at Watkins Glen during the F1 races). They probably go back further, but I don't (go back further that is, I was a ***ager then). These were dense-foam or solid-***/elastomer cylinders, perhaps 1 or 1.5 inches long, by maybe 1.5 inch outside diameter, with a ~half-inch diameter hole along the center of the cylinder so that it could slip over the damper rod. When the dampers moved toward full compression, then the bump *** engaged and increased the spring rate to keep the car from bottoming hard. It was popular to change the shape at the end to be a blunt "nose", to give some progression to the increase in spring rate. Once downforce came in, then the shape/spring-rate of the bump stops became much more important -- at high speed the car's "main springs" will often be the bump ***s. -- Doug Milliken Research Associates Inc.

> downforce must have made them much more desirable. And what > the heck do these things look like anyway? The GPL book > describes them as "cones" as I recall. Are they solid? > Hollow? Hope you have an answer! Thanks for what you've > contributed so far, anyway. Well, they kinda have to have a hole down the middle, don't they? The only bump ***s I've seen are in motorcycles, and they are like donuts but stretched higher (Yeah, that's the official description). The cone-like ones are probably just tapered so that they are thinner from the end the other part of the shock comes from. -- Anssi Lehtinen