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 Post subject: Re: Andy's Brotus 7
PostPosted: April 16, 2017, 5:25 pm 
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Joined: August 8, 2014, 6:08 pm
Posts: 1238
Location: Green Bay, WI
Andy Bro wrote:
Sorry for the odd order of my posts. I'm trying to post up in the order I built it and can go into more detail in there's anything yall are interested in.

More front suspension! :cheers:

The Caterham SV is a few inches wider than their base 7. Conveniently, the stock Miata steering rack width is almost perfect. That said, I designed the steering rack mounts to slide forward/aft, and can shim up as needed. Analytically, bump steer is damned near zero. At the tack welded stage, it was pretty good, but it was hard to get repeatable measurements. As such, the steering rack mounts will get finish welded once I get it back on the ground again.
Attachment:
20160130_145517.jpg

Attachment:
20160402_163439.jpg

Attachment:
20151230_132523.jpg


Now: Shocks.
I have a habit, in case you haven't noticed by now, of making things more difficult for myself. I obsessed on what shocks to get. I've always been a fan of Bilstein, but their adjustable units re just too far outside of my price range. I also wanted to use pushrods/rockers in the front. Problem was: I don't have alot of room between the shock/spring and the steering rack on the driver's side.

I narrowed my search down to small shockbody shocks. I don't remember all of the options that I investigated, but I do remember looking at some AFCO midget coil-overs, and maybe QA1s. In the end, I chose the Bilstein SG line. The damping isn't adjustable, but you can get a variety of valving options off shelf at $90 ea, and they should hold up well. I talked with Bilstein's tech support and got the dyno for the front shocks (SG7-4020 IIRC). I need to measure the final rear motion ratio, calculate the needed spring rate, then I'll be on the phone with tech support again.
Attachment:
20160217_183534.jpg

Attachment:
20160409_121458.jpg


I'm using a set of welded rockers for now. They pivot on oil impregnated, flanged bushings. If they don't hold up well, I'll upgrade to needle bearings and thrust washers, and probably go with shiny aluminum rocker... because racecar.


This is looking really nice. Question on the coilovers. How in the world did you decide on the valving of the Bilstien. I looked at them at couldn't get any answers on the rebound and compression values. can you shed some light on it. I did get answers on QA1 and thought i would go with them. I think a guy could save a few bucks on the one you chose. They do have one that fits my travel too

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My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782


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PostPosted: May 30, 2017, 3:56 pm 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
Tundra 7 wrote:
Andy Bro wrote:
Sorry for the odd order of my posts. I'm trying to post up in the order I built it and can go into more detail in there's anything yall are interested in.

More front suspension! :cheers:

The Caterham SV is a few inches wider than their base 7. Conveniently, the stock Miata steering rack width is almost perfect. That said, I designed the steering rack mounts to slide forward/aft, and can shim up as needed. Analytically, bump steer is damned near zero. At the tack welded stage, it was pretty good, but it was hard to get repeatable measurements. As such, the steering rack mounts will get finish welded once I get it back on the ground again.
Attachment:
20160130_145517.jpg

Attachment:
20160402_163439.jpg

Attachment:
20151230_132523.jpg


Now: Shocks.
I have a habit, in case you haven't noticed by now, of making things more difficult for myself. I obsessed on what shocks to get. I've always been a fan of Bilstein, but their adjustable units re just too far outside of my price range. I also wanted to use pushrods/rockers in the front. Problem was: I don't have alot of room between the shock/spring and the steering rack on the driver's side.

I narrowed my search down to small shockbody shocks. I don't remember all of the options that I investigated, but I do remember looking at some AFCO midget coil-overs, and maybe QA1s. In the end, I chose the Bilstein SG line. The damping isn't adjustable, but you can get a variety of valving options off shelf at $90 ea, and they should hold up well. I talked with Bilstein's tech support and got the dyno for the front shocks (SG7-4020 IIRC). I need to measure the final rear motion ratio, calculate the needed spring rate, then I'll be on the phone with tech support again.
Attachment:
20160217_183534.jpg

Attachment:
20160409_121458.jpg


I'm using a set of welded rockers for now. They pivot on oil impregnated, flanged bushings. If they don't hold up well, I'll upgrade to needle bearings and thrust washers, and probably go with shiny aluminum rocker... because racecar.


This is looking really nice. Question on the coilovers. How in the world did you decide on the valving of the Bilstien. I looked at them at couldn't get any answers on the rebound and compression values. can you shed some light on it. I did get answers on QA1 and thought i would go with them. I think a guy could save a few bucks on the one you chose. They do have one that fits my travel too


I built a spreadsheet (or I did it in Matlab, I honestly don't recall) using the Optimum G's suspension design http://www.optimumg.com/technical/technical-papers/ lectures. Unfortunately, I haven't been able to find it lately, so it looks like I need to redo it. :ack:

So, knowing the wheel rates and motion ratios, it's possible to back out the necessary spring rates. In my searching, I stumbled on this guy:
Attachment:
billy.png


That allowed me to match up the almost arbitrary valving numbers against forces. But, there's no dyno there... So, what's the arbitrary force now? I remember reading that the standard is that it's the force at 10in/s. I took a swag that I needed 4020s for the front and gave Bilstein motorsports a call. Left a message and got an email response. Back and forth a few times got me this:
Attachment:
unnamed.png

Dyno plot of the 4020 shock. I mentioned my spring rate, 300lbs/in to the nice gentleman at Bilstein and he concurred that it should be a good match. Using the dyno plot and the table, I think you can reasonably ascertain what the other valvings should look like in the digressive lineup.

All in all: This is an experiment. I've long been a Billy fan on street cars, but the lack of adjustment on the SG series is only made up by their relative inexpense. If I had room for large-body (46mm) shocks, I may have gone with something that offered some adjustment. My real constraint in the front is that I can't fit big shocks, and the offerings in small body are slim, and get very expensive if you want adjustability.

-Andy


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PostPosted: May 30, 2017, 4:01 pm 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
I'm exhausted.
Attachment:
IMG_20170521_145529351.jpg


-Andy


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 Post subject: Re: Andy's Brotus 7
PostPosted: July 6, 2017, 10:39 pm 
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Joined: August 8, 2014, 6:08 pm
Posts: 1238
Location: Green Bay, WI
Andy Bro wrote:
Sorry for the odd order of my posts. I'm trying to post up in the order I built it and can go into more detail in there's anything yall are interested in.

More front suspension! :cheers:

The Caterham SV is a few inches wider than their base 7. Conveniently, the stock Miata steering rack width is almost perfect. That said, I designed the steering rack mounts to slide forward/aft, and can shim up as needed. Analytically, bump steer is damned near zero. At the tack welded stage, it was pretty good, but it was hard to get repeatable measurements. As such, the steering rack mounts will get finish welded once I get it back on the ground again.
Attachment:
20160130_145517.jpg

Attachment:
20160402_163439.jpg

Attachment:
20151230_132523.jpg


Now: Shocks.
I have a habit, in case you haven't noticed by now, of making things more difficult for myself. I obsessed on what shocks to get. I've always been a fan of Bilstein, but their adjustable units re just too far outside of my price range. I also wanted to use pushrods/rockers in the front. Problem was: I don't have alot of room between the shock/spring and the steering rack on the driver's side.
I've looked at these shocks. How in the world do you go about deciding on the damping to buy them?. they have shocks that would work for me but I couldn't get any answers on the damping numbers.
I narrowed my search down to small shockbody shocks. I don't remember all of the options that I investigated, but I do remember looking at some AFCO midget coil-overs, and maybe QA1s. In the end, I chose the Bilstein SG line. The damping isn't adjustable, but you can get a variety of valving options off shelf at $90 ea, and they should hold up well. I talked with Bilstein's tech support and got the dyno for the front shocks (SG7-4020 IIRC). I need to measure the final rear motion ratio, calculate the needed spring rate, then I'll be on the phone with tech support again.
Attachment:
20160217_183534.jpg

Attachment:
20160409_121458.jpg


I'm using a set of welded rockers for now. They pivot on oil impregnated, flanged bushings. If they don't hold up well, I'll upgrade to needle bearings and thrust washers, and probably go with shiny aluminum rocker... because racecar.

_________________
Steve

My build : http://www.locostusa.com/forums/viewtop ... 35&t=17160

MGB/GT V8 5.0L. viewtopic.php?f=36&t=20782


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PostPosted: July 8, 2017, 12:37 am 
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Joined: September 20, 2016, 3:52 pm
Posts: 17
Location: North Yorkshire, UK
Any Updates Andy? Look forward to seeing any progress! :D


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PostPosted: July 9, 2017, 11:40 am 
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Joined: November 13, 2008, 3:28 pm
Posts: 159
Location: Washington and California
Very nice build. I hope to do similar build


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PostPosted: July 15, 2017, 7:32 am 
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Joined: March 10, 2006, 12:48 am
Posts: 294
Location: CT
Back home from a business trip to Sherrrmany :). Munich is always a good time.
Attachment:
IMG_20170711_200430045.jpg


This weekend's installment: Another lesson in trying to fit 10lbs of crap in a 5lb bag: Cooling edition. Being that this will be a track car, I wanted to try to fit the largest radiator and intercooler possible, and will duct the air in and out help the airfoil as much as possible.

Radiator: Griffin Scirocco radiator
Intercooler. CX Racing Ebay unit

Attachment:
IMG_20170703_152534362.jpg

Attachment:
IMG_20170706_192227237.jpg


I need to get the radiator about .5" lower to have a chance of fitting the 2.5" silicone coupler over the top of the radiator without hitting the nose cone. This may involve relocating the diagonal frame tube about .75" towards the center of the chassis.

I will also probably need to plug the radiator cap port and go to a remote reservoir (oddly, the radiator without the cap port was ~$80 more expensive...).

-Andy


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PostPosted: March 17, 2018, 4:16 am 
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Joined: September 20, 2016, 3:52 pm
Posts: 17
Location: North Yorkshire, UK
any updates Andy? Not heard anything for a while. :D


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