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Learning how to build Lotus Seven replicas...together!
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PostPosted: June 3, 2019, 8:20 am 
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as for the bender itself, you can buy the Eastwood tube bend for about $200. I can't build it for that.

10" CLR is a really odd sixe. That will drive your purchase price for the two hoops way up. You can always go with a 7" die and add some shoulders instead of a single bend.

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PostPosted: June 5, 2019, 3:32 am 
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Probably too early to estimate the under - over. I'm going to pour some tooling Urethane to try to make the surface of the 10" CLR die. The outside molds are pretty much done. The core needs to be machined yet, it's made out of various scraps of foam all glued together.

Wish me luck!


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PostPosted: June 6, 2019, 4:21 am 
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The under is looking better.

Foam core plug melted when I tried to fix a goof with Bondo. I don't know if it's some chemical or heat of cure that just melts the styrofoam. So I quickly formed (heh) a new plan to make the mold core out of 2x4s. That worked good.

After sanding the wood core, I covered it with carnuba auto wax and let it dry. I sprayed Universal Mold Release on everything and let that dry. Clamped the mold together.

Then I mixed the 10 lbs of mold urethane that only has a 6 minute pot life. It literally set up at about 8 minutes.

Sprung a leak because each half of the form molds distorted due to the weight of the Urethane. I was able to stop most of it with duct tape!

So about 1/2 hour later we got a very hot Urethane Die, ready to be finished. It's supposed to reach about 8,000 psi compression after 7 days.


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PostPosted: June 10, 2019, 2:01 am 
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If this casting seems like it might work (50:50?), I'm gonna order steel to make the bender and reinforce the die. That'll be about $200, then the steel for the hoops is under $100.

I needed a break from stressing about the roll hoops so I got all the parts out of the basement and assembled it as much as I could.


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PostPosted: July 5, 2019, 2:49 am 
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Man is it hot and humid out, ugh. But I got some more metal in for the roll hoops. And some more to try to build a tube-roller-bender.

I bought 3 little pulley looking dies for my roller, 9$ a piece, couldn't go wrong.

So here's what I got going on with the roller-bender so far. I was planning to put sprockets and a chain on the lower outer dies so they will both drive the tube to be bent. And then I need to add a monster wheel to one of those shafts to try to turn it and drive the tube through it.

A guy I know said to fill up the tube with sand and weld plates over the end to help prevent squishing the tube.


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PostPosted: July 6, 2019, 6:56 am 
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The chassis is looking great. It's nice to mock up to remember the end goal.
The humidity has been unreal here also.
There is a post here where a member shows how he bent thin wall tube using packed sand.
You have thick wall tube but it would hurt but it needs to be bone dry if you are welding on caps.

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PostPosted: July 6, 2019, 1:14 pm 
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Well good news and bad news. The good news is the basic idea of the bender works and the strength is there. Bad news once you get to about a 45 degree bend the tube starts squishing out over the short rollers.

When the roller dies showed up I was a bit disappointed that they didn't go at least halfway up the tube and that is where this failed.

I just kept rolling it to see what would happen and could only get to about a 90 degree bend before the tube was squished too wide to go through my machine anymore.

Maybe I'll try to figure out how to make the ends of the roller larger diameter to go up past the middle of the tube. 3/8" plates might work, then weld up the tip to blend to the plate.

Or I could think more on my original tube bender design.


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PostPosted: August 3, 2019, 3:17 am 
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Well I tried to work on the rear shock mount. Lot of plates with lots of angles. It was really pushing my welding skills, at one point I had the tungsten out 5/8 past the collet. Pretty tricky to get all those deep welds.

They'll fit right on the rear corner of the frame at the back and hold the body of the shock.


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PostPosted: August 3, 2019, 9:57 am 
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I'm just catching up a little on your build log. The chassis looks great, as does all the detail items of the suspension. I got a little laugh from the mock-up of the seat. I understand what you're doing, and that you're very capable, but the visual of that wooden seat in this high tech chassis made me think of those "as seen at WalMart" photo series, if you know what I mean.

Don't take it personally. It was just visually funny. You're going to have a totally cool build when it's done.

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: August 4, 2019, 1:59 am 
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Mock-up seat? What mock-up seat? haha....

I also made molds for the bushings a while back and cast them in a 70 shore urethane. The deep part of the mold (green) is cast in a soft silicone for extraction purposes (mold for that not shown). It sits in chunk of 2x6 I found lying around. The other half is delrin which I put giant bleed holes in to prevent trapped air. I tried smaller bleed holes but the urethane got stuck in those. The larger holes allow me to remove the whole casting in one piece. Then I just clip off the excess with a side cutter.

Even though it's delrin, I Johnson's Paste Wax it just to be sure, it's still sticks a little bit.

I made 8 sets which took about a week! 16 hour cure time per set.

I greased them with some moly type grease and test fit them. There's not a lot of preload on them so I might need to make them bigger or harder shore, but they are surprisingly smooth and stiction free at this point.


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