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Learning how to build Lotus Seven replicas...together!
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PostPosted: November 9, 2017, 10:31 pm 
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I'd probably start with mounts for the lower control arms rather than the strut mounts.

If you start with the things you know need to be strong, and build off of those, you might end up with something closer to what you want.

I also like to use drafting paper and draw by hand the basic shape in the first stages, but maybe that's just me.

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PostPosted: November 10, 2017, 1:59 am 
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Joined: January 10, 2008, 4:47 pm
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Location: Massachusetts
Here's a picture f some work I did for a midi frame with a Subaru. This doesn't seem like a complete version of the drawing, for instance the transaxle seems to have disappeared. Someone had asked how to lower the upper rail thru the cockpit area so it has that. I was working on a version with a tall roll hoop for the windshield but it isn't shown here.

Thins to notice though are how the rails support the suspension arms and springs. I would avoid the many bends you have in your rails. They aren't that easy to make really and they are so much weaker than straight pieces of metal. Single bends aren't that hard but you can't just stack 90 degree bends one after the other in different directions, the bender gets in the way.

Draw in some suspension arms and think about how the force from the springs gets fed into the chassis.


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PostPosted: November 10, 2017, 9:09 am 
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thnaks guys. My drawing was not showing the lower crossmembers. I'm actually using it from the subaru. All i have to do its tie in the rear of the control arm to the chassis which i have layed out in garage. Im basically just replacing my forester's body with a tube frame. All the suspension and drivetrain geometry remains identical to the Subaru Forester

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PostPosted: November 11, 2017, 8:18 pm 
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Tried pipr bender today. Lots of disapointment.


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PostPosted: November 12, 2017, 2:26 pm 
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What type of a bender? Can you give us a picture? The picture I put above is not much use, despite you having AWD in the title somehow I thought you were going mid-engine. Maybe need to stop posting at 2 AM.

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PostPosted: November 13, 2017, 4:12 am 
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terryjr wrote:
I'm actually using it from the subaru. All i have to do its tie in the rear of the control arm to the chassis which i have layed out in garage.



Even so, there appears to be a number of gratuitous bends in your sketch. You will be miles ahead following the advice of directly connecting of your hard points (think straight lines). The best example might be your main roll hoop to rear suspension. Why have the back to back 90° bends from the hoop lower leg to the rear cradle? Make a fixture to receive the cradle and then put a straight piece of tube from that to the main hoop. Hopefully that makes sense?

The straighter your connecting tubes are between your nodes, the more rigidity is achievable and it theoretically improves the ability to manufacture as well.

Chris


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PostPosted: November 13, 2017, 8:30 am 
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ckouba wrote:
terryjr wrote:
I'm actually using it from the subaru. All i have to do its tie in the rear of the control arm to the chassis which i have layed out in garage.



Even so, there appears to be a number of gratuitous bends in your sketch. You will be miles ahead following the advice of directly connecting of your hard points (think straight lines). The best example might be your main roll hoop to rear suspension. Why have the back to back 90° bends from the hoop lower leg to the rear cradle? Make a fixture to receive the cradle and then put a straight piece of tube from that to the main hoop. Hopefully that makes sense?

The straighter your connecting tubes are between your nodes, the more rigidity is achievable and it theoretically improves the ability to manufacture as well.

Chris


makes sense. straight lines will be more rigid than curves. I guess i was trying to get too cosmetic. The rear still has to be detirmined. It has a crossmemebr very similar to the front, and a large fuel tank that sits in front of it. Im now thinking of making it even more mini truck like with a small bed in the back. which should also give me the fuel tank cover the state might require

the bender is a 12ton HF style. I got it working much better as the day went on by grinding the dies down to make a better fit to the pipe.


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PostPosted: November 14, 2017, 9:20 am 
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Bent first real tube last night. I still have to make and fit bracket to it and get the levels and protractors on it but its close. The tube is still deforming a little but I think it might be from the temperature, its about 45F in garage. I may try to heat the bend area up with a torch before bending anything over a 45° angle

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PostPosted: November 15, 2017, 12:17 am 
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you can try packing the tubes with sand too. Sounds funny but it helps stop them from kinking.


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PostPosted: November 16, 2017, 8:47 am 
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coupel brackets made to connect crossmember to the chassis

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PostPosted: November 18, 2017, 3:04 pm 
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Gettin some small stuff done. Finalized bends on crossmember mounting pipe and got bracket on.

Image

Then worked on one of the two control arm mounts. Fit some flat bar in tube notcher and cut into at about 30 degrees to hug pipe darn near perfectly. Need to go get a new 1/2" drill bit

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