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Learning how to build Lotus Seven replicas...together!
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PostPosted: August 4, 2011, 5:55 pm 
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Back from page 2 again, which raises a philosophical thought. Is LocostUSA an active forum? I believe the evidence is clear on the basis of build logs. If you don't post for five or six weeks you disappear to page 2! So we have a community of active, engaged builders. I guess I'm less active: not slow; more like intermittent! :)

I finally bent up my 'real' windshield frame. (The truth is, my nephew is coming for another visit and I must show some progress!) The mock up windshield frame was exhaust tubing, to avoid 'experimenting' with expensive DOM tube. The mock-up also provided a basis for change: I raised the fore-and-aft bend two inches higher in the final to move the exposed part of the windshield forward enough (+1 inch) to make more room for defroster vents in the scuttle. Photo 1 shows the bracketing locating the windshield frame. The brackets are 1/8 in. plate, as are the doublers that carry the bottom of the frame.

Today I finished fitting the roll bar braces. That project started with flanging and forming 1/8 plate to carry the bottom ends of the braces. Much banging and sweating (swearing?) was required since I don't own a shop press. My chassis aft end is very Lotus-like and this part of the frame is not in a single plane, unlike the Book design, and so required a twisted plate. By flanging 1/8 plate I avoided adding an addition stiffening tube, which might have been easier in the long run.

I bent the braces to open up the top of the 'trunk' deck, but sadly I bent two right hand ones - oh well, recutting skewed fishmouths is good for character. The bend in the braces will ultimately be bracketed to the rear tubes for better buckling resistance. The tops of the braces are only tacked. I will finish welding them with the chassis off the build table. My normal position welding is OK, but gets ugly rapidly in vertical or overhead situations. I plan to roll the beastie over to make life easier, and the welding better.

A sharp eye will notice some structure missing under the rear spring mounts/roll-bar mounts. That is getting nearer to my 'to do next' list.


Attachments:
Windshield Frame bracketing.jpg
Windshield Frame bracketing.jpg [ 33.85 KiB | Viewed 2672 times ]
Roll bar and braces.jpg
Roll bar and braces.jpg [ 50.53 KiB | Viewed 2672 times ]

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Warren
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Build Log: viewtopic.php?f=35&t=11601
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PostPosted: August 4, 2011, 6:17 pm 
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Great to see the progress! Keep it going!


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PostPosted: August 4, 2011, 9:18 pm 
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sadly I bent two right hand ones - oh well, recutting skewed fishmouths is good for character.


Yo Warren!
It'll also get you an honorary membership in Team Slotus! Congratulations... I think....

The car is looking good, Sir! Is that windshield frame that goes to the floor also the "front hoop" of a roll cage? If so, shouldn't it be mounted to the frame at the bottom, and not to the floor sheet metal? If I missed something along the way, lemme know...
:cheers:

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Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: August 5, 2011, 6:26 am 
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JD,

No, I'm not actually trying to build a roll cage, just a more robust windshield frame that will serve as a hand-hold for entry-egress without risk of damaging either the windshield or the scuttle. As an earlier post shows (sketch below repeated) I also intended to test fit up some links between the windshielfd frame and the roll bar, but I may not use them in the end. My windshield frame and roll bar will not meet the broomstick test and I am afraid that the fore and aft bars will be low enough to become head-knockers (ouch!). A mock-up will be required, although Jeep-type rol bar padding might be added to deal with a marginal situation.

Although the windshield frame is not a cage per se I see your point: even with the 1/8 doubler plate, a rollover might peel the floor off. I will look at supplemental bracketing to link the bottom of the frame to the bottom frame rails - but that will have to await rolling the chassis over so that I don't have to weld out-of-normal-position! :oops:

Thank you for raising the issue.


Attachments:
Warren_Windshld_RBar_2 (Large).jpg
Warren_Windshld_RBar_2 (Large).jpg [ 62.42 KiB | Viewed 2632 times ]

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 Post subject: Re: Supplemental to JD
PostPosted: August 5, 2011, 8:04 am 
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JD,

Here's my thoughts on brackets.

As the sketch shows (Option 1) I could make brackets with 45 degree breaks on them. They would be fillet welded to the windshield frame and the lower chassis tube. I could get two brackets per connection.

Option 2 is an intreaguing (spelling?)option - a simple flat bracket that would be fillet welded to the frame rail and plug welded to the windshield frame - but it would have to be twice as tall as two Option 1 brackets to get the same weld length (and shear strength) as two Option 1 brackets.

But neither will get done until the frame is on its side, so I can weld in normal position.


Attachments:
Winshield Bracket Sketch.jpg
Winshield Bracket Sketch.jpg [ 365.47 KiB | Viewed 2620 times ]

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PostPosted: August 5, 2011, 8:09 am 
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I don't see how it can easily separate from the floor, as it is attached firmly to the upper rail too. Maybe a very short gusset made from 1" tube attached to the top of the lower frame rail would be enough to strengthen it enough. Add to that, 2 fillet welds at the tangent to the upper rails and I think that should suffice.

Have you checked that the front tube doesn't interfere with your leg when clutching?

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PostPosted: August 5, 2011, 8:32 am 
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Chuck,

Thanks for the various suggestions. The gusset based on 1x1 tube is an even more elegant solution. I will add the 'tangent fillets' on the upper rail too.

I did check out interference with the clutch pedal leg and it feels fine. That's with imaginary pedals of course ....

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PostPosted: August 5, 2011, 10:02 pm 
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Hey Warren and Chuck-
I kinda like "option 2" but I can't quite say why. Seems like it would give more rigidity to the whole assembly. I'm trying to envision Chuck's idea, and if I "see" it correctly, it sounds good too.

As you pointed out in your first response, this isn't a "roll cage" per se, so I really should hush and let you build your windshield frame as you intended. It would do exactly what you said, be a strong point that driver and passenger could grab for ingress/egress without worrying about cracking the scuttle.

However, if you decide to put some reinforcement at the base of the frame, I think it would be stronger overall and help a bit in a "worst case" scenario. Just my two cents worth, but for you, no charge!
:cheers:
Regards-
JD Kemp

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: August 6, 2011, 7:54 am 
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JD,

Here is my understanding of Chuck's bracket ... It's an elegant solution that would transfer vertical loads in the tube to the bottom frame rail quite well.


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Chucks Bracket.jpg
Chucks Bracket.jpg [ 99.02 KiB | Viewed 2562 times ]

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PostPosted: August 6, 2011, 8:30 am 
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Yep. That is exactly what I envisioned. In the case of a vehicle upset, it might put a focused load on the lower frame rail. It is reinforced vertically by the upper rail too. However, the roll bar function is not the goal of this application. My intention was to prevent making a 7/8" wide pocket that "stuff" would accumulate and be difficult to get out. Have you seen all the stones and gravel after a short drive? It seems the chorter drives are the worst.

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PostPosted: August 6, 2011, 9:21 am 
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Hey, that design looks good! Exactly what I had envisioned... It would make the windshield frame much more "roll-over" safe, I think.

Long ago and far away, some friends of mine (husband and wife) were running a hillclimb, sharing a TR4. The wife crashed, badly. The floorboard metal was ripped open, and her foot went thru the opening. That was about 30 years ago, and Janet still kinda limps sometimes.

So, please forgive me for nagging you about your windshield frame. I have good intentions, I promise...

JD Kemp

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Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom


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PostPosted: August 6, 2011, 9:49 am 
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Warren, are you intending for the scuttle to be permanently attached? As drawn, the welded-in hoop would prevent its removal.

I've been grinding along at a similar problem for a few weeks now. The simplest and most practical way I've come up with so far would be to weld the scuttle down permanently and make it simple for the dashboard to come out for access - mainly, making sure the wires are long enough.


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PostPosted: August 6, 2011, 5:18 pm 
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TRX,

Yes, I have decided to make the scuttle permanent, at least after the glass goes in the windshield frame. I will cut large openings in the forward face of the scuttle and close it up with an aluminum panel. The dash may be removable, or fixed, but definately accessable from the cut-away forward face. I hope (a long way away yet) to do a lot of the wiring (wipers aside) before the scuttle is permanently fixed.

[Edit: if you ran another tube for the bottom of the windshield glass and butted the scuttle top against that (like pook/b-t's build), the scuttle could be removable, if leaky. I decided against that because I need (vehicle inspection requirement) to install defroster vents, and landing the base of the glass on the scuttle makes that easier to do.]

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PostPosted: August 6, 2011, 10:44 pm 
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Access ports would certainly work. There's been more than one time I've been tempted to take the nibbler and make one on some car I've been working on...


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PostPosted: August 9, 2011, 7:06 pm 
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Just a short progress report.

This week I sent in my second build report to the engineer/inspector, and overall he seemed happy. (His goal is to ensure that the car is acceptable when physical inspection time comes.) We had a good follow-up discussion about tying the windshield frame into the frame rails, which he too recommended. He noted that even with my doubler plates the main field of the floor would need to be 1/8 in. thick itself to avoid punch through - bracketing to the frame rails is much more weight efficient!

Today I mocked up the longitudinal bars between the windshield and the roll bar, using exhaust tubing. I was concerned that there might be a 'head knocking' problem, but there proved to be lots of clearance (see photo). There is a slight bend in the link tube so that part of the tube is horizontal, more for esthetics than anything else.

I then proceeded to cut and bend my precious remaining DOM, which was only just long enough to get two pieces. You can see the two pieces, with their 5 degree bends lying on the transmission tunnel. Unfortunately, you may also see that I had a Team Slotus moment and bent one tube on the short side of the die mark (the green tape) and the other on the long side. :ack:

I may be able to avoid buying a whole length of DOM though. The friend who loaned me the bender had a 'moment' in his rally Subie

http://www.youtube.com/watch?v=6L-BGXV_ ... r_embedded

and will be bending up a new radiator support frame out of 1 1/2 DOM. I hope that he might be able to use my 'mistake' and that I might get a piece of his DOM.

I am in no hurry at the moment. I'm fed up with hacking and filing tubing notches and have ordered a tubing notcher from Aircraft Spruce. Delivery is a couple of weeks, which aligns with time lost due to a couple of regattas at which I will be judging, not to forget that I have to uncover the septic tank for the quadrennial visit of the honey wagon.


Attachments:
File comment: Mock up of windshield-roll bar link using exhaust tube. DOM versions (one bent incorrectly) lying on transmission tunnel, without notches
Windshield Rollbar Link (Medium).jpg
Windshield Rollbar Link (Medium).jpg [ 87.21 KiB | Viewed 2475 times ]

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