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Sorry for the thread hi-jack, but I'm a little concerned about your numbers botbasher. Lets see how strong my Excel-Fu is: Please check both my logic and math for errors before taking any of this as being correct.

A 2:1 ratio means that you'll only have 3.78 inches of total wheel travel from full droop to full bump. I know nothing about your target weights, but for the sake of argument I'll guess ~1500lbs GVRW (at fully loaded max capacity the car will ever see) for a BEC and a 50:50 weight distribution. The 2:1 ratio and 550lb springs on such a car will provide a reasonably firm 1.9Hz ride frequency, but will also mean that 1G of suspension loading will use 2.73 incehs of wheel travel of your 3.78 total. Now I don't know of anybody who has hard data they are willing to share on how many G's of available compression are required for adequate suspension travel on a given type of car, other than a some third hand (or worse) numbers I've seen for designed wheel travel on a few production cars, but I personally wouldn't try for any less than 1G and would probably recommend more just to be on the safe side. So if you want a minimum of 1G worth of suspension travel available in bump, and by definition the car will require 1G of force sitting at rest, then you'll need enough pre-load on the suspension that you'll only have 1 inch of droop from a resting state. In this case it would be about 60% preload. Of course this is not taking into account the bump stops, which it sounds like you would be hitting a significant portion of the time anyways, especially if you want to decrease the preload at all to increase droop.

In order to get 6 inches of total wheel travel from 1.89 inches of shock travel, the ratio would be 3.175:1. Using the above data the ride frequency would be 1.2HZ with a 1G suspension loading of 6.87 inches wheel travel...And the preload required would be over 100% resulting in 0.0 inches of available droop.

In other words the better you want motorcycle shocks to work given their limited travel, the more directly they must act on the suspension, but the more stiffly sprung the car will become. My personal preference for a motorcycle shock is the Suzuki Hayabusa rear shock, which while not being as attractive looking, or pacakaging, than some of the fancier units provide the best combination I have found of longer shock travel (measured 2.0" to the bumpstop, [/i]supposedly[/i] 2.8" total) and higher spring rate (99-07 = 732lb, 08+ = 810lb) to allow more effective use of ratio reduction in an automotive suspension.

Edit: According to the Race Tech web site, the spring on an 07 R1 shock is ~525lb.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Kurt... Oh, how I've missed your "input". No... it wasn't wishful thinking that got me 6" of travel... it was what you hate working with.. trial and error. Without hitting the upper stop I have 5.75" of travel on the wheel and 1.89" of travel at the shock. I'll go dig out my notes (somewhere in that pile of boxes out in what I now loosely call "the garage") and confirm the numbers if you really need it.

No, I don't believe that those stock springs will give me the right wheel rate and fully expect to have to change them (I believe we've "talked" about this before), as should almost anyone that decides to use motorcycle shocks. As an outboard unit they posses none of the qualities we need from a shock (as previous builds and threads can attest to), but as an inboard unit, we can use levers, cranks and positional changes to make them more (notice I am not saying perfectly) suited for our needs. All I'm using them for is a great place to start from given that they came complete, they're cheap, they're plentiful and there are lots of aftermarket replacements for them.

Driven... Yes, your right.. that would bring me up a bit short on the travel wouldn't it? 2:1... 3:1... what's in a number? I should know better than to type on a phone while sitting in a meeting!

Yes, I know that the current spring rates are horrible for the application. I fully expected them to be. Honestly, I don't ever expect to drive on these. Those numbers are tough to work with (Your Excel-Fu is strong!! ) and I fully expect to change not only the springs, but will probably evolve into a set of Ohlins that are tailor made to the task. Possibly with a bit more travel to ease those borderline numbers. Do you have the specs on those 'Busa shocks? Never looked at those.

Check those numbers again with the true 6" travel and see if they are not a bit more palatable. Do you have a link or can you post that Excel sheet? Might be a good warm up to get back into the car by measuring and plugging in numbers!

So as the recap.. the springs stink.. I know this and have a plan. I have 6" of travel at the wheel. My memory is bad.. I did try a 2:1 and determined that 4" of travel was not nearly enough (IMHO). And my typing (at any time of the day) requires a through vetting.

Sorry for the threadjack oddsaabs.. although not entirely unrelated to the current topic, we did drag it a bit away from your original question. We can discuss this more in my build log if so desired.

Cheers!

KS

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Never become a pessimist. A pessimist is correct oftener than an optimist, but an optimist has more fun, and neither can stop the march of events.-Robert A. Heinlein

I brought up the squared term because if a builder isn't aware of it and read this thread, they could make some large "design" mistakes.

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Basher, no bashing... He made a reasonable point and if your going to buy Ohlins, just say so.

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Took some time to enlarge the stock hayabusa bellcrank bearing hole to accept the spherical bearing. I used a stone cylinder and drill to make it just big enough to press the bearing in along with a bit of red locktite. Sure doesn't feel like it's going anywhere anytime soon, but it will be a spot to watch during break in and development once the car is on the road.

Still need to work on packaging the shock and bellcrank. I've got it working properly with the rocker on a cross member that puts the pushrod above the top rail. I'd like to find a way to keep the pushrod under the top rail, but that's rather challenging. I'll play with it some more and let you know how it works out.

No worries with the thread-jack. It's an interesting discussion.

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Jonathan
Building a ZX14 powered Locost.

"Go out hard, when it hurts, speed up." Matt Carpenter

His reasonable point isn't permitted if it's in response to a post from me. Has it been that long that he shouldn't be able to remember that we were warned by a mod to not comment directly on each others posts. End Of Story.

Remainder of comments taken PM,

KS

_________________
Check out Firearm Finishes & Coating for options to ceramic coat your Locost parts. Hundreds of stock or custom colors including Chrome and Clear Coating options now available! High Temp options for hot bits!! Plastics too!!

Never become a pessimist. A pessimist is correct oftener than an optimist, but an optimist has more fun, and neither can stop the march of events.-Robert A. Heinlein

oddsaabs,

Is there something above the rails your trying to avoid? There are several variations I've seen where the bellcranks are above the rails and they work nicely. The defining factor seems to be the length of the shock as it's difficult to bring it under the rails with proper geometry if the shocks are too long. Too short and you simply raise the lower mount. I was tempted to do this, and still might, but I am trying to keep the holes in the nose to a minimum.

Mine happen to fit under the rails, but a mounting capable of holding the pivots was an absolute bear to create given the type of crank I am using. Can you detail out the geometry on the 'Busa crank? Might be easier for me to take a pair per side and modify them to work with the existing setup. Probably end up copying Rod version. Pic bleow.

Just how long did it take for you to hone those out?

Cheers,

KS

_________________
Check out Firearm Finishes & Coating for options to ceramic coat your Locost parts. Hundreds of stock or custom colors including Chrome and Clear Coating options now available! High Temp options for hot bits!! Plastics too!!

Never become a pessimist. A pessimist is correct oftener than an optimist, but an optimist has more fun, and neither can stop the march of events.-Robert A. Heinlein

Same reason. Aesthetics meets functionality.

Didn't take too long. Maybe 20 minutes of grinding. Add in the multiple test fits and I spent an hour or so getting it to press in correctly.

The Busa shocks are a bit longer than the R1's. They also have the cartridge at the bottom which makes fitment a bear. I've gone around the block a few times with them now and keep ending up where I started; with the pushrod over the top rail and the bellcrank on a fore-aft cross member a few inches in from the side.

Thanks for the pic and the input. I'll post what I come up with as it gets closer.

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Jonathan
Building a ZX14 powered Locost.

"Go out hard, when it hurts, speed up." Matt Carpenter

Yeah, that can be a real bear, especially depending on the importance to the individual!

I looked at the 'Busa shocks on eBath and had a thought, now that your a expert in installing sphericals. Have you thought about mounting it pressure can up?

I didn't attempt it with my version because that put the non-bearing end in bind when it ran through it's range of motions. Maybe now that the bearings are an option, you could "flip" the mounting and free up some space and eliminate some interference issues.

Depends what you have for clearance on the other side as well, but it's another packaging option!

Cheers,

KS

_________________
Check out Firearm Finishes & Coating for options to ceramic coat your Locost parts. Hundreds of stock or custom colors including Chrome and Clear Coating options now available! High Temp options for hot bits!! Plastics too!!

Never become a pessimist. A pessimist is correct oftener than an optimist, but an optimist has more fun, and neither can stop the march of events.-Robert A. Heinlein

Great idea. But now I have to start thinking upside down as well. Damn, my head hurts.

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Jonathan
Building a ZX14 powered Locost.

"Go out hard, when it hurts, speed up." Matt Carpenter

Glad you already knew the spring rates weren't going to be sufficient with your design! Not sure what other specs might be looking for that I can provide, but shoot me a PM if there's anything you want me to measure on one. [/Thread Jack]



oddsaabs: If you aren't able to put a snap ring into the rocker, were you able to you bore/press them each rocker from opposite sides such that the slight angle of the pushrod coming in will push the spherical bearing against the lip, such that it could help prevent it from loosening from its position?

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

No lockring, just a tight fit and some locktite. These bellcranks are cheap enough that Over the winter I'll give a pair to my friendly neighborhood machinist to do this correctly. Mostly for now I want to see that it can work.

So I've attached a few pics of the current set up. 3" bump, 2" droop. Translates into full use of the shock travel with the bumper engaged at 2.5" bump. Still have a little tweeking to do with the the lower mounts, but the rocker placement is pretty much there.









Thanks to everyone who helped out with this.

New question:
Right now the rack is in line with the steering arm holes. Is that correct, or should it be fwd or aft an inch or 2? Big can of worms I know, but thought I'd ask anyway.

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Jonathan
Building a ZX14 powered Locost.

"Go out hard, when it hurts, speed up." Matt Carpenter

Drill 2 small holes and use some screws to locate either side of the bearing.

From ride height to full bump I can only see falling rate in your rocker but can't clearly see what your LCA to pushrod angles are doing at the same time, have you actually compared the wheel rate to shock rate?

Cheapracer brings up a very valid concern based on the pictures above. If you haven't already, you may want to measure your shock travel in 1 inch (or better yet 1/2 inch) incriments of wheel travel to see whether it's increasing or decreasing over the each portion of the wheels range of motion.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

Oh now your just getting picky. I finally figure out how to get this thing working and your concerned that it won't work correctly. Jeez, detail details details.

I checked the wheel movement to shock travel this evening before diner and found the rate pretty constant until the very top or bottom of travel. Through the middle 3" of travel (2" bump to 1' droop) the shock moves a constant 1/2" per inch of wheel travel. The final 1" of bump is hard to measure because the bumpstop engages and begins compressing part way. The final 1" of droop becomes a bit shorter at 5/16, probably due to the bellcrank maxing out it's throw. I think this can be adjusted via pushrod length later during setting ride height and corner weighting.

_________________
Jonathan
Building a ZX14 powered Locost.

"Go out hard, when it hurts, speed up." Matt Carpenter