In reply to Dusterbd13-michael :
Interested...that puts ride frequency 1.6-1.7 Hz. Still have to figure out how to compress the spring almost a whole inch, but it's worth a try.
And yep, these GSXR springs are 2.5" ID x 3.5" OD with roughly 1/2" coil wire diameter. Just like most aftermarket coilover springs. The body of the shock is 2.25" OD.
In reply to maschinenbau :
Done deal man. Just got to figure out how to get them down to you.
Awesome.
I like the strut solution, both for the cost and because the 1:1 motion ratio means you don't need a super fancy shock to get decent damping.
If it doesn't work out well, whats stopping you from moving the mounting point for the current gixxer shocks a bit further back to give a little pre-load? Would you need to compress the spring to install?
In reply to Run_Away :
Yep that's the problem - not enough preload on the spring. If I moved the coilover mount closer to the rocker, I would need spring compressors just to install the rocker levers and/or coilovers, due to no slack in the system at full droop during install. It's easier to just put a longer spring inside the coilover (or spring spacer).
I like the strut solution too for the same reasons. I hope it works out with packaging.
I have a pair of Koni Sport struts on the shelf that were incorrectly labeled and I got to keep them when replaced with the correct ones- 15" collapsed length, if that would be workable.
In reply to ¯\_(ツ)_/¯ :
Those would be awesome if 15" isn't too long. I need to benchmark first with the Daewoo 13" struts and will let you know if I have more head room.
I know you will have less travel, but why don't you just drill a hole closer to the pivot for the wheel side of the rocker?
Doesn't that do the same thing as upping the spring rate?
Either way, it would be a quick proof of concept.
In reply to Robbie (Forum Supporter) :
Pushrod angles get all messed up
The best thing about this project, as said before, is that it's half custom fab and half restoration. When I'm burnt out on one, I can do the other. I hate suspension right now, so how about the steering column.
Goodness this is a lightweight column. The housing is paper-thin aluminum tube. The thicker steel rod is actually hollow, so the thinner steel rod can collapse into it. No U-joints, just a rag joint straight into the rack. I love how simple and light this unit is. These parts were RUSTY. This is after knocking all the rust off. Also pictured is the pedal assembly - a whole 'nother project in itself.
The steering wheel is ground all the way to the frame. I assume this is for the horn, since power comes from a single wire slip ring, which means it must ground through the steering shaft. Funny things about fiberglass cars.
Instead of a u-joint, early Europas use a "rag" joint that is actually a steel disc. There are 2 little conical rubber grommets for each of the 4 bolts, which could use refreshing. The bolt themselves are safety-wired since they are only compressing rubber. The original joint is P/N FAM1718 which I can buy new for $45 or replace with an "equivalent" TR6 (and standard for later Europas I think) u-joint P/N 145377R for about the same. There are also universal 9/16-36 spline options. Seems like a surprise budget hit no matter what, unless I slap it back together as-is.
The shaft rides in the housing on these little bushings. Some kind of plastic sleeve inside a metal bearing inside a rubber bushing. All are pretty hammered and stuck. It was a pain getting them out. I think I can turn some 1-piece bushings out of delrin and send it.
Also, I need a steering wheel? On the lookout for anything simple, classic, and 3-spoke. It's a simple 6-bolt hub.
Don't worry, I did some custom fabrication too. Strut housings are now modified for Daewoo Lanos / Toyota MR2 / Koni aftermarket inserts. Basically anything with a 13.5" long body. I extended the bottom 1", the max amount before hitting the axle boot at full droop.
May not look like much height difference, but the insert rod (right) compresses all the way in, while the Avalon one (left) sticks out about 1.5" at full compression. For the same total travel, I now have about 3" more head room than before. At ride height, the rod will be about half extended - just over 3" bump. Now I need some way to retain the insert in the housing. On normal inserts, the housing is threaded for a hold-down nut, but mine aren't, and that tap is like $300. I might try to include something in the spring sleeve it to keep it held down.
I haven't given up yet on the rocker pushrod. Those springs are en route courtesy of Dusterbd13! So this could all be wasted effort.
In reply to maschinenbau :
On the inserts for my rx7, they have a bolt that goes through the bottom and hold the insert in. Is this a possibility for this setup?
In reply to wvumtnbkr :
That's a good idea. I think even the Konis might have that too. I'm afraid to drill/weld on these particular inserts, but I could switch to RX7 ones for that feature. Do you have years or P/Ns? It's hard to tell on Rockauto which ones bolt in from below.
Can you weld on the top of a strut housing with the threaded nut?
What are your plans for the pedals? I can take some pics of what I did if you want to do something similar. Bronze bushings and a balance bar setup, untested of course.
In reply to Brotus7 :
I could do that, but I don't have those housings and they'd go in the Challenge budget. Unless I bring my pipe-cutter to the junkyard...
I'm hoping to use the Toyota booster/MC with the stock pedals. I've seen your setup and like it a lot. I may need make a linkage that goes up over the steering rack, because the wide booster may hang below the frame otherwise. It's automatic for now, but I'll keep the clutch pedal for when I'm ready for the E153 trans swap.
Can you weld a flange on the top and just bolt a plate down and keep all that within the spring diameter? Make a cap that bolts or rivets in? Have a colar/cap that you weld onto the housing but not the insert?
maschinenbau said:In reply to Brotus7 :
I could do that, but I don't have those housings and they'd go in the Challenge budget. Unless I bring my pipe-cutter to the junkyard...
I'm hoping to use the Toyota booster/MC with the stock pedals. I've seen your setup and like it a lot. I may need make a linkage that goes up over the steering rack, because the wide booster may hang below the frame otherwise. It's automatic for now, but I'll keep the clutch pedal for when I'm ready for the E153 trans swap.
I have 2 pairs of 1989 lemans struts that I'm about to toss from my lemons car. Threaded and everything. I could cut them up and send for the cost of shipping.
In reply to SDet :
That would be awesome if you don't mind cutting the top 1" or so of two of them! Should fit in a flat rate envelope.
In reply to maschinenbau :
Just catching up for about 3 pages... lookin' good.
I like the shortened struts for their simplicity, for dependability. Prolly a good plan.
I like the coil over/rocker for the cool factor! Lots of us don't have the math to do that right, so props for that.
On the spring compressor, the right motorcycle shock rebuilder could just put the taller springs on (or spacers) for very little. If you find the right one! (wish I could recommend one... do have a guy in Fuquay-Varina might can help)
maschinenbau said:In reply to SDet :
That would be awesome if you don't mind cutting the top 1" or so of two of them! Should fit in a flat rate envelope.
I'm too new to pm, been following this build, saw mentions of the lemans and thought, I can help.
I'll let you know Monday.
maschinenbau said:Some ride freq calculations:
I think you have an Error in whatever math you are using to determine ride frequency. If your Wheel Rate is 265lbs and your corner weight is 460lbs your Ride frequency is 2.37hz. The calculation for ride frequency I've always used for my bellcranks is Frequency in hz using Lbs/in and Lbs weight for mass is 187.8/60*SQRT(Wheel Rate/Sprung Mass), in CPM you just drop off the 1/60.
The other issue I see is your relationship from Spring Rate to Wheel rate needs to be a squared term. Wheel Rate = Spring Rate * MR^2. (I ususally do MR as Spring / Wheel so what you have as 2.0 I would express as 0.5). So your first column has a Spring rate of 530lbs/in and a MR of 0.5 so your wheel rate is 132 lb/in. This gives a Suspension frequency of 1.67 Hz. The problem with this setup is that at a MR of 0.5 and a ride frequency of ~1.7 Hz you need a shock that has 3.4" of travel and you have much less then that, which explains why the rideheight was off.
It's possible I am just interpreting your data incorrectly and you have the correct math behind the scenes. I plugged your numbers into the spreadsheet I used for the LMP360 and to get an acceptable Shock travel to Wheel Travel at 1.7 Hz you would need an ~1000 lb/in spring. You can use a much more reasonable spring rate if you are willing to accept a ride frequency of 2.3-2.5 Hz but that is likely too different then your front suspension and will result in a car that spends all it's time oversteering.
So I think your best bet is going to be either Struts at the back that get you closer to stock ride frequency, or re-do the belcranks with more like a .7 MR and stiffen the front to correspond to the 2.5 ish HZ ride rate, because I'm not sure your shocks would like to dampen 1000lb/in springs that would move over nearly the entire travel with frequency.
In reply to nocones :
You're definitely right about the wheel rate calculation. Thankfully that didn't factor into my ride frequency calculation, which does use the squared term. I used metric for frequency because I hate converting pound mass. Not sure what I did wrong here.
I still feel good about my math. Alright, we got a bunch of springs, including an ebay kit I bought only for the perches because it was so cheap.
Turns out those fleabay perches don't actually fit a real 2.5" ID spring, so I helped them.
Starting cutting up more parts for the upper perch so I can reuse the Avalon's strut bearing.
...and it's just not going to work. I did a lot more careful measuring of the Lotus body. There is simply not enough room for a McPherson strut, even if they were 2" shorter than I've already made them. There is a flat fiberglass panel that connects the outside skin to the inner shell that would have to get cut. That's not a big deal, except then you have zero access to the strut hat for installation. I invested a lot of work into the struts, but I'm glad I know for sure now.
It's been a bummer of week trying to figure this out. So I went back to crux of the problem - can't put the coilover mount in the right spot, because there's enough droop allowed by the Honda UCA ball joint. I was so stuck on adding preload, or a stiffer spring. My math says if I could just move the coilover mount closer to the rocker, by having a lower droop point, I'd be good.
So let's test that. I ripped out the Honda control arm and made a dogbone from the ends of more Toyota Avalon rear suspension links. I just tacked them on the frame and the Holy Bracket. This actually puts $40 back in the budget.
Without the shock, I tested the range of motion. Basically unlimited until the rocker goes vertical. And then tacked the coilover mount just about 1/2-1" further rearward than I previously could. And put the coilover in. And added weight...and...
It's damn near perfect! The right side is supported at target ride height with the 2 blocks. Left side is sprung. It's almost 1" too high, which is good because there's more weight to add. This is also max preload, so I can come down more. The jump-up-and-down test feels way better than before. Not racecar stiff, just sports car firm. And that's uhh without shock damping...more on that soon.
Of course the test dogbone is not enough for the wheel torque, so it will evolve into a proper triangulated UCA. Of course using recycled Avalon toe links.
So that's all great. But why is the shock not damping? In a stupor of exploratory frustration, I accidentally over-loosened the damping adjuster and all the oil poured out. I tried to refill with fork oil, but now it's jammed closed and I can't retract it. I don't know what happened but it's definitely berkeleyed. Luckily these are ubiquitous on ebay, so I can just replace.
So that's not a lot of actual progress. In fact I think I went backwards, from a functional parts perspective. But I finally have a clear path forward. I was obsessing about this problem for so long. I was researching pretty far out there for alternatives, including high-dollar actual car coilovers and even torsion bars... Now I just have to execute.
Win-win !
Glad you found a solution, and bonus that it's cheaper too
Hell yeah man, that's awesome! Figured it out, and put money back into the budget!
Crushing the progress, makes me want to get back to my own project
Simplify and add ebay parts!
Been following this in the background and you're further along with it than anyone else who owned it from what I can follow!
Don't know what coilovers you're using but I have one from a cbr600 you can have for free if you want.
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