Russ doesn't seem to rush into anything, and researches everything. My guess is, he already has the info, and has a good idea of what he plans on doing.He always starts very interesting threads like this one. I've spent hours reading them, on this board and others, just to learn what I need to do from what he has already researched. Great thread Russ! i'm going to replace my knee actions with real shocks next days off, so this is great info!
Shocks are on an angle for two reasons one is to moderate the effect so as to perfectly tune the suspension. For instance a shock at 45 % will have a softer effect on suspension than one that is vertical. It also lends some lateral stabilty to suspension although probably not a huge amount. For the last two cars I built room and shock length also played into it. I do not like them straight up and down but 45 is as far as i would like to have to go with maybe 30 degrees from vertical being desired
I have always thought that "one" of the reasons shocks are on an angle is to make there effective travel longer. If a car has say 3" of vertical travel then a shock mounted on an angle will have greater than 3" of compression and can be better tuned over that length. This is starting to get interesting. Peter
Conceived in a hansom, delivered in a hansom, or a good-looking little guy? That avatar has a distinctly UK look to it.
Yes, but I only think that works if the shock has too little effective travel mounted one way, and then "gets back" its full travel if leaned over a bit. Gary
If we're talking about early Fords, and I think we are, you might look at the attitude the first tube shocks or direct-acting shocks Ford had on their cars in 1947-48, and the retro-fit Houdaille conversion kits available at the same time. On the earlier cars, 35-41, the front shocks were mounted with eye studs perpendicular to the frame rail sides and the bottom of the shocks at a slightly forward angle from the tops with virtually NO side to side angle at all. The later ones , 42-48, the front shocks were mounted with the shock eye studs parallel to the frame rail sides and the lower eyes slightly outboard of the uppers at pershaps a 15-20* angle. In the rear the shock studs were mounted in a parallel to the frame rail sides fashioninside the frame rail to the rear crossmember with a slight outboard angle to the bottom brackets near the wheels. That's the way it was.
Here are some good calculators, they are mainly for springs rates, but if you play around with them you will understand the relationship of how a shock is positioned affects its dampening properties. In its simplest form: The further outboard away from the center of the vehicle and more vertical your shocks are, the stiffer they will be. You could take the same shock and move it 1' inboard and angle it in 30* and it will act way softer than out by the wheel sitting vertical. http://www.swayaway.com/calculators/diagrams_if_A-ArmModel.html http://www.swayaway.com/calculators/swayawayCalc.php http://www.swayaway.com/calculators/MainCalcUserGuide.php
Something that has come to mind reading all these posts is! We say and mostly agree that by laying the shocks on a greater angle gives it more distance to move along and softens the ride which is accepted. It just seems funny that expecting a shock to travel further with all that built in resistance, why should the ride be softer, you would think that all the extra resistance thru a longer travel would be applying the opposite effect. I know it is not correct in the real situation, but you can see how folks come to conclusions that are far from right. I am still curious about different shock angles with respect from front to rear axles and I dont mind hearing about how it was and how it developed and how it is now, as long as I and others can learn one good fact or rule of thumb from all this I will be wrapped. Shocks are just one of those items that seem to happen but a lot of guys not know the little 1% tricks that could help heaps.
dude! that manbaby shit has me spitting all over my keyboard! as creepy the image is it's funny as hell! shit i can't even remember what the thread was about, somebody getting shocked? WTF!
One other thing regarding setting up the shock in relation to the pivot of the axle. The only thing that has to be a certain way is the mounts, the mounts of the shocks should be perpendicular to the axle or you could get some binding. The angle does not matter for binding especially in a street driven car with limited travel. To validate that statement, here is what I used to build, a scratch built tube buggy with 18" travel airshocks, it used every bit of the 18" up front and the shocks were mounted vertically with no binding. If you look really closely of the buggy flexed out in the one picture you can see the shaft of the shock fully extended on by the left tire.
It's a good thing I read this post this morning! I'm just beginning the shock mount process on my new build. It's always nice to have have plenty of input & points of view! Thanks!
Regarding your question as to why shocks are sometimes mounted on an angle:<O</O <O</O Short answer is: for packaging reasons mostly. Long answer is, well, a very long answer...<O</O <O</O First, shock absorbers aren't even shock absorbers, they're dampers. Contrary to popular belief, they don't simply control the wheel/axle assembly when disturbed but actually "dampen" the entire vehicle in a variety of modes. So its important not to think of a shock absorber simply controlling 1 wheel; the front has a contribution to the rear and vice-versa. In other words, you need to think of them as a system each contributing a certain amount of control/stiffness to vehicle.<O</O <O</O First, each vehicle has a unique frequency and stiffness determined by tires, springing, wheelbase, chassis stiffness, etc. Each one of these factors contributes to how the vehicle PITCHES (see-saws about its centre) and HEAVES (bounces up and down vertically). These modes are active whenever the vehicle is moving and occur at different frequencies to each other.<O</O <O</O The damper's job is to minimize the amplitudes of these modes in order to reduce load variation (better traction) and minimize disturbances (better ride quality). It should be noted that these resonances occur at very low frequencies~ 4 to 6hz (or 4-6 times per second). However, they are quite important to how the vehicle behaves and feels to the occupants.<O</O <O</O Now, the next thing the dampers do is influence the response of the vehicle. A key thing to remember is that dampers are VELOCITY sensitive, not displacement sensitive. They have to be moving in order to work and they have no idea of how far theyve moved. That's why we describe/measure damper forces in units of FORCE VERSUS VELOCITY. So a typical road car damper is then built to achieve a certain amount of force for a given shaft velocity. This is tested using a shock dyno over a speed range of 0 inches/second to more than 20 inches/second. (Off-road racers test at incredible shaft speeds, over 20 FEET/second!)<O</O <O</O The vehicle's handling response is mostly influenced by the low-speed compression force in a given damper. This force is generated at very low shaft velocities~0-1"/second. From there the forces ramp up to a given/desired force that is typically defined by ride-engineers in real world road testing. This would be in the 1/sec to 5/sec velocity range. This range is important as it contributes a lot to the perceived ride quality. Too soft and the car just wallows, too stiff and you get a very harsh ride like a steel-wheeled skateboard.<O</O <O</O Above velocities of 5/sec is where the majority of the pitch and heave cancelling occurs. This is usually developed using a 4-post shaker rig where the vehicle is excited over a decaying sine wave of varying frequencies and amplitudes. (Usually starting at large amplitude/low frequency and the decaying to high frequency/low amplitude). This rig allows a known, measureable amount of energy to be introduced into the vehicle. Sensors then return the amount and amplitude of disturbances that the vehicle sees. From there, dampening is finely tuned to minimize these variations.<O</O <O</O So, in summation, its a very complex relationship and there is no simple answer as to which damper you should use and at what angle it should be mounted. Barring some very expensive testing equipment, my advice would be simple trial and error Just remember that adding more angle reduces the damper's velocity and and they need velocity in order to work. <O</O I hope this helps your understanding a bit and I must add that this screed only begins to scratch the surface of dampenings contribution to vehicle performance.<O></O>
Nice write-up Rat L. Can...and reading your racing back ground, I can see your knowledge. Thanks, I learned something. I would like to read more along this lines as well as suspension design, have any recommendations, web site or books? Thanks to fiftyv8 for this tread, hope it does not stop too soon, great stuff coming!!!
Any of Carroll Smith's "...To Win" books are quite good and are straight-forward, easy reads. If you really want dip into PhD waters, the industry "bible" would have to be Milliken's "Race Car Vehicle Dynamics". Expensive but worth it if you're truly interested understanding and quantifying vehicle dynamics. All of the above are available on Amazon http://www.amazon.com/s/ref=nb_ss_gw?url=search-alias%3Daps&field-keywords=carrol+smith
Thanks for the book lists, "Race Car Vehicle Dynamics". $257.00 Canadian...ouch... may have to pass on that one.
$257.00!? Amazon is showing it at $99.00 USD. I'm an ex-Hoser (Montreal), so I understand the exchange isn't very good but, Jesus, that's taking advantage, eh!
Since you asked, one rule of thumb would be to mount the front shock as close to the ball joint as possible, and in the rear as close to the wheel as possible. They should be as close to vertical as possible for maximum effectiveness. Increased angle from vertical decreases effectiveness and moving inboard requires more dampening and less control,
Ya, I went to amazon.ca $257.00, amazon.com $99.00 There's a book store on Bloor St. in Toronto that some how has great deals,I'll check it.
Is there any simple rule of thumb stuff that could help guys decide what shocks or what specs to look for in a shock that works better in say 30's hot rods. tried and proven stuff with Im beam axles etc. Or advice that would help if folks were to say go and weigh their vehicle or take weights on each wheel or what ever else could be good advice in this department. I know if I could get say 5% improvement is say my handling or ride simply by making a better decision about a product in an area I dont really know much about I would be very pleased.
Thanks for the suggested reading material. I read the reviews for Herb Adams' Chassis Engineering on Amazon - mixed overall but sounded like an ok stating point. I'll check out Smith's reviews next. There's a lot of great info on this board - thanks for sharing.
The biggest challenge there is that, typically, the weight distribution in the average hot rod is terribly biased to the front. We take older cars that didn't weigh that much to begin with, then strip them down further and fit over-sized engines. So that doesn't help much. Next, the springing then gets biased poorly to cope with the weight distribution along with the ride height & rake we're after. Having said as much, if one was particularly industrious (and patient) you'd get a set of old FOX shocks and a revalving kit. Start with a basic valving and then begin using the adjusters. Start on the compression side first and wind in some bump force until it begins to feel harsh. Back it off a bit and call that good. Next, feed in some rebound until the ride feels more "controlled". The settings won't necessarily be the same front-to-rear. From there, you'd send your shocks to someone like "PRO" shocks and ask them to valve their single tube shocks to match the forces you've come up with. This assumes you're running a traditional car and don't want a set of 80's canister shocks hanging off of it...If you had a Kustom, you might just leave the FOX shocks on. A lot of work but it can be done. And, as usual, once you know a little you realize there's a lot more to be learned...Fun, huh?
Carroll Smith's books are excellent primers on a variety of subjects including fasteners, rivets, welding, fabricating, etc., plus do a good job of scratching the fundamentals of handling and ride. They're a perfect place to start for anyone wanting to build a safe, reliable race car or hot rod.
Slightly O/T, Not much is ever said about hot rod construction when it comes to vehicle weight and (dare I say it) comfort. For example, say you had this nice riding rig, be it a Caddy or a BMW or Benz. And then you says to yourself, how can I select the springs and shock valving to give me the same kind of ride on my hot rod? How does the math work on that? Can a ratio or relationship between one car's weight, springing, shock valving and suspension travel be related to another car under construction that has a different weight? Just wondering, Gary
This whole discussion is very interesting, one that I've studied for a very long time.....then, when I went to engineer my 1935 sedan chassis, I wanted a decent compliant ride with good chassis control. So......I started looking at different late model vehicles where all the engineering had already been done by those guys in the white coats and pocket protectors. I found my example in my own driveway...my wife's 2003 Chevy Avalanche! It rides well, handles well and seems to have reasonable chassis control. The rear has coil springs with shocks mounted as far as possible to the axle ends, a large diameter sway bar all tied together with a four-link and panhard bar setup. The only variation from conventional thinking is that the shocks at the top lean toward the REAR of the frame rather than inboard at the top. I built my '35 chassis almost exactly like that truck except I used coil-overs.......and guess what??, it rides and handles pretty damn good. Actually it handles better than any hot rod I ever built which I partly attribute to DW's (Welder Series) rear sway bar kit and a little bit of race car kinda fabrication. Why not borrow from those high paid engineers and R & D departments.
^^ Exactly. Beg, borrow, steal where applicable. However, if you're after a certain "stance" you'll sometimes have to give up ride and comfort to achieve that "just right " look. Another factor is is torsional stiffness. If you're running a '32 frame, for example, the stiffness is so poor that achieving a plush ride is very challenging without going to quite soft springing, which equals rather high-ish ride heights. From there, it's having rigid enough mounts for your shocks so that they're actually dampening, not simply twisting their mounts out of the way. Personally, I'm happy to give up the ride quality to get that bitchin' stance I'm after!
I've got the Herb Adams book, and it is definitely worth the price. It's a little thin, but still very helpful. I also have Fred Puhn's How to Make Your Car Handle, which is a fantastic book. Even if you aren't setting up the car for turns, it's great information on suspensions. Practical and theoretical information.
U like RatLCan, set up idea,To add a bit of easy tuning, place a tie wrap on the shock tube at ride hieght.Go and take her for a spin, then check the position of the tie wrap. This will give a good indication of travel,and with the adjustable shock just dial in a little more or less dampening. No mention of stops here, also very important to prevent broken components.
Actually, the tie wrap will only show you the biggest bump you hit on that particular route. Again, dampers ARE NOT displacement sensitive, only VELOCITY makes them actually do something. In other words, if you went around a turn at very high speed, the total roll of the vehicle would not be influenced by the shocks, only the rate at which the vehicle accumulated roll.
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