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PostPosted: September 18, 2019, 12:42 am 
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Johnsinski wrote:
I've also been trying to get more quotes for the roll hoops. One company came back with
<snip>
$2800...no joke. Wouldn't an ethical company just say "we're not interested."
Well gosh, it looks to me like they're going to have to tool a custom die just to do your job, and that could well account for the first two grand of that quote. It sounds like they were interested. What do you consider an ethical labor rate for custom tooling?

I'm not being a smartypants here. Back in the day, I've been extremely interested in some projects, and I gave the clients perfectly ethical six figure quotes because there was nothing off the shelf that would do the job. The secret to cheap fab quotes for small lots is to ask people if they can do things where the answer is "Oh heck yeah, we do that all the time."

The alternative is to buy bunches of it. If you were going into production it wouldn't be such an issue. Your first custom tooled roll bars might cost you $2800, but now that they have the tooling, the second pair might be 5% of that ($140).

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PostPosted: September 18, 2019, 8:17 am 
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JackMcCornack wrote:
Johnsinski wrote:
I've also been trying to get more quotes for the roll hoops. One company came back with
<snip>
$2800...no joke. Wouldn't an ethical company just say "we're not interested."
Well gosh, it looks to me like they're going to have to tool a custom die just to do your job, and that could well account for the first two grand of that quote. It sounds like they were interested. What do you consider an ethical labor rate for custom tooling?

I'm not being a smartypants here. Back in the day, I've been extremely interested in some projects, and I gave the clients perfectly ethical six figure quotes because there was nothing off the shelf that would do the job. The secret to cheap fab quotes for small lots is to ask people if they can do things where the answer is "Oh heck yeah, we do that all the time."

The alternative is to buy bunches of it. If you were going into production it wouldn't be such an issue. Your first custom tooled roll bars might cost you $2800, but now that they have the tooling, the second pair might be 5% of that ($140).


Best answer I've ever seen for one off custom work compared to production.
The 10" CLR of your hoop bend is truly odd size. Options are change design to accommodate common die sizes, pay for custom dies, or find someone with a state of the art CNC bender that can change bend radius with programming instead of dies. Those machines are about 2 million dollars so the cost of running them for one offs is still quite high.

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PostPosted: September 19, 2019, 12:06 am 
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Just to clarify, all the quotes I've gotten are based on an 8" CLR. I totally get economy of scale. What concerns me is when the low and high quote differ by a factor of 32! But, that's why you get quotes I guess. ;)

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PostPosted: September 19, 2019, 10:50 am 
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Man, $2,800? Are you sure someone didn't mistakenly put the decimal point in the wrong place? Now $280 is something believable.

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: September 19, 2019, 10:53 am 
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Did you check prices with Jimmy at rollcagecomponents.com? Very good work, very fast and very economical. Used by several of us here.

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PostPosted: September 19, 2019, 11:40 pm 
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I got a great quote from rollcagecomponents.com.

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PostPosted: September 20, 2019, 9:47 am 
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That was quick. OK then, move onward.

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PostPosted: October 3, 2019, 12:36 am 
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Just catching up on this amazing build!

Johnsinski wrote:
The angled inner wishbone mounts are just kind of visually placed. "The Book" says that taper will help anti-dive and squat. I do have anti-dive and anti-squat designed in from the side view. I will look at the fore-aft movement of the wheel when the suspension moves.


Just wondering what you found out about this. I am by no means an expert but I haven’t seen anything that uses the “tapered” style to gain anti dive/squat. (Only seen the side view angles to cg) I’d love to know what else it changes during cycle as well! Just making my frame and always open to more options to make my build take even longer...

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PostPosted: October 4, 2019, 9:26 pm 
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Well I did some graphs of the axle height vs other measurements. Axle height of 0 is ride height, it goes from about -2" to +5" (-2 being full droop and +5 being fully compressed).

- Caster goes from about 4.9 to 6.1
- Camber goes from about -1 to -4.3
- Fore Aft motion of the axle goes from -.04" (negative is shorter wheel base) to 0" to -.11" (kind of weird)
- Toe goes from .43 (out) to .1 to .5

When I was futzing with the original design, I was mostly just shooting for zero changes in the above measurements.

I'm not sure what all that means, hopefully it means it''ll handle good! And hopefully I'll find out someday! Good luck on your project too.


Attachments:
Camber_Caster.jpg
Camber_Caster.jpg [ 44.04 KiB | Viewed 1147 times ]
Fore Aft Toe.jpg
Fore Aft Toe.jpg [ 44.36 KiB | Viewed 1147 times ]

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PostPosted: October 6, 2019, 2:41 am 
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I received the 2 roll hoops from rollcagecomponents today. They look great for $85. I'm sure the $2800 ones would have been greater. ;)

I milled a quick and dirty mold from a 2x4 and some bondo fill to make the motor mount rubber and have been pouring those over the past few days. They seem about right. One side is flat and it's other side has a cylinder boss sticking up about half the thickness of the motor mount plate. I'll need to make some washer-like spacers so I can adjust the height. There will be a crush tube that need to be cut to a length that will pre-load the rubber a little bit.

I use the same urethane I used for the suspension bushings. A 70 shore, I think. I "Johnson paste wax" the molds before each casting, but the urethane rubber is still hard to get out, needs more draft, or the molds should be made of silicone. Pro tip: Demold at about 15-20 hours, not 50, it seems to stick more with the longer cure.

I turned some inserts for the pushrod/tie rods and welded those in. I "plug welded" (can't think of the right term for that at the moment) 2 spots around each insert, and of course around the seam. I'm sure I ordered jam nuts, but I can't find them.


Attachments:
motor_mount_pushrod_01.jpg
motor_mount_pushrod_01.jpg [ 198.09 KiB | Viewed 1103 times ]
motor_mount_pushrod_02.jpg
motor_mount_pushrod_02.jpg [ 186.21 KiB | Viewed 1103 times ]

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PostPosted: October 6, 2019, 6:14 am 
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Your flange mounts will be much stiffer and stronger if you wrap the edge with 1/8x1/2 strip. It will make a huge difference but I don't know that you need it based on this picture. It is the difference in bending loads on 1/8-1/4 plate versus 1/2 inch plate. Just fyi.


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JOHNSINSKI crossection.JPG
JOHNSINSKI crossection.JPG [ 53.36 KiB | Viewed 894 times ]
JOHNSINSKI crossection.JPG
JOHNSINSKI crossection.JPG [ 53.36 KiB | Viewed 1101 times ]

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Last edited by Miatav8,MstrASE,A&P,F on December 1, 2019, 6:40 am, edited 1 time in total.
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PostPosted: October 6, 2019, 9:44 am 
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@Johnsinski

What material did you use to cast the rubber? That would be useful to know for me (& others too).

Thanks,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: October 6, 2019, 3:31 pm 
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MV8, yea I can see putting some side skirts around that to beef it up a bit. The engine is only about 150 lbs, maybe 200 with the diff.

This urethane is from Smooth On, it's PMC-770. It mixes to a translucent amber color, so I also got a black dye to mix in. The "part a" must be particularly sensitive to humidity as the almost empty bottle had semi-cured over the summer. They sell a "dry gas" to put in the bottle before re-closing it. I wonder if argon would work just as well?

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PostPosted: October 6, 2019, 5:35 pm 
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@Johnsinski

Thank you!

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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PostPosted: November 26, 2019, 3:05 am 
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Looks like the DB got restored, yea! I was about to start a part 2 thread.

Quickie updates since the server crash:

Roll hoops welded in and filling in braces. Before I started welding in the braces there was a fair about of twist in the frame, maybe 1/4" at 4 feet wide over the length. So I clamped it down to my big CNC table and then cobbled up some levers to get rid of the twist. Then I strategically welded in some of the braces that would hopefully "shrink" the diagonal and fully welded those in, it actually worked. By visual inspection with straight edges at each end of the frame, it looks straight now.

At some point I decided the engine was just too far over, So I moved it maybe 1.5" to the left and then I will need different length axles, oh well.

Now with the roll hoops in, I'm trying to model up a foam seat. I'm hoping to scan the foam, take it into CAD and clean it up, make it symmetric and all that. Then CNC mill the appropriate mold from foam to make a buck for making a fiberglass seat.

I also finally got the front suspension done enough to actually support it. By using the various hole options on the rockers I get approximate rates from 55lb/inch to 155lb/inch. That's for the front end total, not each shock rate. I would guess with driver in the car the sprung front weight will be 300ish lbs (technical jargon). The rear sprung might be more like 400ish lbs.

Jumping up and down on it with a middle setting feels maybe a bit soft, but feels good too.


Attachments:
roll_hoops.jpg
roll_hoops.jpg [ 235.46 KiB | Viewed 1015 times ]
engine_mounted1.jpg
engine_mounted1.jpg [ 271.23 KiB | Viewed 1015 times ]
seat_foam2.jpg
seat_foam2.jpg [ 218.68 KiB | Viewed 1015 times ]
seat_foam1.jpg
seat_foam1.jpg [ 242.42 KiB | Viewed 1015 times ]
front_suspended2.jpg
front_suspended2.jpg [ 255.48 KiB | Viewed 1015 times ]
front_suspended1.jpg
front_suspended1.jpg [ 238.65 KiB | Viewed 1015 times ]

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