LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently July 19, 2018, 3:26 pm

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 35 posts ]  Go to page 1, 2, 3  Next
Author Message
PostPosted: December 14, 2017, 7:03 pm 
Offline
User avatar

Joined: May 27, 2006, 9:46 pm
Posts: 1838
Location: BC, Canada. eh?
I know this has been discussed before, but I have a thought or two, and would like some opinions.

First, I really don't like the idea of wrapping the side panel at the bottom of the frame over the floor (i.e., the floor sandwiched between the thin side panel & the frame). It would definitely be visible from the side of the car (my alloy body panels won't be painted) as a step, of sorts, and would look unfinished IMHO.

The thought I had was to trim the floor panels by 1/2" around the outer edges (only where the alloy side panels will wrap around the bottom of the frame in the cockpit area), so both the floor & alloy panels will have 1/2" each for attachment & would butt up against one another along the underside of the outer bottom frame tube.

To preface, my floor is 1/8" hard aluminum, currently held in place with a total of 28 1/4"X20 allen-head stainless steel countersunk bolts, through reinforcing plates welded around the inside of the periphery of the floor area, secured with S/S nuts. Of course, I plan on using a sealant or construction adhesive to seal the floor, separate the aluminum from the (soon to be 2-part epoxy painted) frame, and to possibly add a little structural rigidity. I don't know what alloy the floor is made of, but it's VERY hard & tough. It's anodized, and hard enough that I went through 7 bimetal hacksaw-type fine tooth jigsaw blades cutting it. When you tap it with a hammer, it doesn't go "tink" like aluminum usually does...it goes "taaaannnnggggg" like a bronze bell. and keeps ringing for quite awhile.

My buddy doesn't agree that my floor attachment plan is strong enough. To attach the floor in his Locost, he's using 48 5/16"X28 bolts & nuts, structural aircraft adhesive, and a couple of hundred Cherry-Q rivets to secure his floor.

Personally, I think that's a bit overkill, and is likely adding weight & reducing strength in the main frame tubes by drilling hundreds of holes in them, but that's just my opinion.

Should I also add rivets, as well as the adhesive & bolts, to secure my floor, or do you think it will be strong enough with my existing plan? I should add that, with just the bolts in place (most of 'em, anyway, and none of them tight yet) I can jump up & down in the car without the floor flexing (I'm no lightweight, either, at 6'2" & 210 lbs.). I'm thinking that with the rest of the bolts in place, plus a structural adhesive, it should be plenty.

The alloy body panels will likely also get some structural adhesive, as well as some copper rivets to hold the bottom of the panels in place (although I'm not certain even these are necessary with the structural adhesive).

My plan was to drill as few holes in the frame as possible to retain the structural integrity of the steel, and so far, I don't have a single hole in any of the structural parts of the frame (everything that needs attachment currently bolts through welded-on tabs). That would change when I rivet the side panels on on the underside of the frame of course, but I'd like to use as few as possible for the aforementioned reason.

I know there are no right-or-wrong answers, but there are extraordinarily knowledgeable people here whose opinions I value greatly!

:cheers:

_________________
Scratch building, at continental-drift speed, a custom McSoreley-design framed, dual-Weber 45DCOE carburated, Zetec-engined, ridiculously fast money pit.

http://zetec7.webs.com/


Top
 Profile  
Reply with quote  
PostPosted: December 14, 2017, 11:00 pm 
Offline
User avatar

Joined: June 8, 2010, 8:02 pm
Posts: 539
Location: White Rock, BC, Canada
Couple things:

-The floor is there for more than just holding your feet up. It's to act as a shear panel and is probably the single largest contributor to stiffness on the typical Locost car. Pure adhesive, or sparse bolts will not allow the floor to act as a shear panel. Rivets are really the ticket here. Also adhesive and aluminum can be prone to failure: I wouldn't trust adhesive alone unless you have professional experience with it.
-Why not just use a brake to get a nice angle with no step, and overlap the floor? There will be a small air-gap, but side panel will be snug against both the side and bottom of the tube (adhesive this panel if permanent).

Cheers.

_________________
Build log: viewtopic.php?t=9291


Top
 Profile  
Reply with quote  
PostPosted: December 14, 2017, 11:36 pm 
Offline

Joined: June 5, 2016, 7:03 am
Posts: 198
Location: ontario
when I rivet the side panels on on the underside of the frame of course, but I'd like to use as few as possible for the aforementioned reason.

I know there are no right-or-wrong answers, but there are extraordinarily knowledgeable people here whose opinions I value greatly!

:cheers:[/quote]

Yes there is no right or wrong way to make the floor. For what it is worth (2 cents) here is what I have done on both my builds and why. First I have never considered drilling and riveting the tubes. This is, I know, a controversial opinion but since 2004 (when I started building sevens) I have not changed my mind on this. My approach is to weld sheet steel to the bottom of the tubes every where . I have used .050''pre-galvanised sheet steel. For rigidity I have rolled half inch beads strategically. I believe that a steel floor provides a good surface towards chassis stiffness and safety of the driver. In the .050 -.055'' the weight is acceptable, I think.
:cheers:


Last edited by phil on December 17, 2017, 7:29 am, edited 2 times in total.

Top
 Profile  
Reply with quote  
PostPosted: December 15, 2017, 5:08 pm 
Offline
User avatar

Joined: July 4, 2006, 5:40 pm
Posts: 1918
Location: Novato, CA
I have to say, after close to 50K miles with a welded steel floor, my Locost is as rigid and squeak-free as the day I finished it.


Top
 Profile  
Reply with quote  
PostPosted: December 15, 2017, 5:54 pm 
Offline
User avatar

Joined: May 27, 2006, 9:46 pm
Posts: 1838
Location: BC, Canada. eh?
Thanks to everyone for their input!

I'm committed to the alloy floor, as 1) I already have it, and 2) it's already cut to shape, drilled, and mounted (bolts only, at this stage).

In consideration of those who advocate rivets for attaching aluminum floors, I've decided that's what I will do. I'm figuring on using Aircraft Spruce-sourced Cherry Q stainless steel aircraft rivets (they're self sealing, and a pieced of the shank remains inside the rivet body, for added strength), and for a sealant (between floor & frame) I plan on using T-88 structural adhesive, also from Aircraft Spruce. Its working conditions for application fit my circumstances well (one type I looked at requires maintaining the shop at a minimum of 75*F for several days - not likely, in an unheated garage in the Pacific Northwest in winter!!), and it's plenty strong in itself, so it adds to the structural strength of the floor, in addition to the rivets. It has a tensile strength of 7,000 psi, a lap shear strength of 2,000 psi on aluminum (both values vastly higher than those for the SS rivets!), and can be applied down to 35*F.

I'm still trying to come to the grips of the problem that the side of the car will be lower by almost 1/4" from the firewall back than from the firewall forward (due to the thickness of the floor itself + the side body panel lip riveted over it), but a narrow line of flat black paint on the lower 1/4" might hide it. I'll have to see how it looks.

Cheers, gentlemen! :cheers:

_________________
Scratch building, at continental-drift speed, a custom McSoreley-design framed, dual-Weber 45DCOE carburated, Zetec-engined, ridiculously fast money pit.

http://zetec7.webs.com/


Top
 Profile  
Reply with quote  
PostPosted: December 15, 2017, 10:54 pm 
Offline
User avatar

Joined: June 8, 2010, 8:02 pm
Posts: 539
Location: White Rock, BC, Canada
If your front-side panels aren't formed yet, you should be able to match the height one way or another. Even if you have to add some shims to drop the panel the required amount.
FYI, I found some steel-body/shank sealed rivets that were considerably cheaper than the Cherry rivets. I've forgotten where from (Fastenal?) but it's worth a look.

Cheers.

_________________
Build log: viewtopic.php?t=9291


Top
 Profile  
Reply with quote  
PostPosted: December 16, 2017, 2:11 am 
Offline
User avatar

Joined: May 27, 2006, 9:46 pm
Posts: 1838
Location: BC, Canada. eh?
Thanks! That's a good idea, putting a 1/8" shim under the frame from the firewall forward. Easy to do, and it would eliminate the step completely!

BTW, I plan on making the side panels forward of the firewall removable, via Dzus fasteners. The increase in accessibility is enormous and, not having a lift, will make even everyday tasks like oil & filter changes a snap, not to mention the battery, starter, etc. accessible from the side while sitting on a stool. How civilized! I'm getting too old to lie on my back to work under cars...my decrepit old back is unforgiving these days... :roll:

_________________
Scratch building, at continental-drift speed, a custom McSoreley-design framed, dual-Weber 45DCOE carburated, Zetec-engined, ridiculously fast money pit.

http://zetec7.webs.com/


Top
 Profile  
Reply with quote  
PostPosted: December 20, 2017, 6:43 pm 
Offline
User avatar

Joined: May 27, 2006, 9:46 pm
Posts: 1838
Location: BC, Canada. eh?
For those of us in Canada, I've located a new source for rivets and other fasteners, right here on Vancouver Island - http://www.strathcon.com/category-list.aspx . Not only is there an online store, but a physical store as well!

Prices are very competitive, shipping is very reasonable, and emails to the company are answered almost instantly. I was going to buy my rivets from Aircraft Spruce, but my new store is cheaper, for the same items, and the selection was better as well. I needed some S/S rivets with S/S mandrels, with a grip range of .251" - .312", a size which Aircraft Spruce doesn't carry. The tensile & shear strength are the same as the Aircraft Spruce SS/SS Cherry rivets.

I'm using roughly 150 rivets (range .126"-.250") for the main periphery of my floor, and 60 (range .251"-.312") for the outer edges, where they'll be holding on outer body panels as well.

Total cost, with shipping & tax, is $49.62CDN. Considering I've seen these same rivets listed by retailers elsewhere in Canada for as much as $1.26 each, it seems pretty good.

_________________
Scratch building, at continental-drift speed, a custom McSoreley-design framed, dual-Weber 45DCOE carburated, Zetec-engined, ridiculously fast money pit.

http://zetec7.webs.com/


Top
 Profile  
Reply with quote  
PostPosted: December 21, 2017, 9:32 pm 
Offline

Joined: May 1, 2012, 9:43 am
Posts: 316
Location: Medicine Hat, Alberta, Canada
Good find with the store! I might be ordering some stuff from there.


Top
 Profile  
Reply with quote  
PostPosted: December 22, 2017, 10:24 am 
Offline
User avatar

Joined: August 11, 2011, 12:38 pm
Posts: 242
Location: Akron, NY
I riveted my floor on and bought my Rivets from https://www.rivetsonline.com/. They had the best prices that I could find anywhere when buying in larger quantities at the time.

I may be worried about galvanic corrosion using a stainless steel rivet in aluminum sheet. I used stainless structural rivets for the steel to steel and where the rivets went through the aluminum sheet I used aluminum structural rivets.


Top
 Profile  
Reply with quote  
PostPosted: December 23, 2017, 1:03 am 
Offline

Joined: February 2, 2017, 1:02 am
Posts: 38
Location: Illinois
I haven't seen much talk about welding the floor around the whole perimeter. I was told doing that improves stiffness but the amount of welding wire and gas that would take has to be incredible. Anyone out there building a car with this method?


Top
 Profile  
Reply with quote  
PostPosted: December 23, 2017, 9:03 am 
Offline
User avatar

Joined: September 22, 2005, 8:12 am
Posts: 1459
Location: 4AGE in S.E. Michigan
Yupper, Welded all around the perimeter of the floor pan. But I would weld only about a foot at a time and then switch to a different location on the pan. Allowing things to cool down for each section. You would probably exceed the duty cycle on a 110V welder with that much continus welding too. The only issue is that you end up with a swimming pool if caught out in heavy rain. But you would have the same problem with rivets and a sealer. Others have also added an "X" weld pattern in the floor to to shrink the pan after welding the perimeter. I bead rolled the center section of my floor pan before welding. Both methods should reduce oil canning. Dave W


Top
 Profile  
Reply with quote  
PostPosted: February 19, 2018, 3:24 pm 
Offline

Joined: November 18, 2016, 6:57 pm
Posts: 2
After much agonising--I made my floor in .058 sheet steel cut to fit the bays between tubes--rolled-in 1/2 inch beads to make more rigid.Welded in by small increments to avoid distortion--and yes-it took a lot of wire & gas and DAYS of time-but the result is rigid and tight. Finished the tin with cold-galvanising paint & truck-box liner coating in & out. Tough & non-skid rough finish . I want to do stainless on the outer body panels--Anyone know what Gauge/thickness & s/s grade works best ? Planning on a 1 1/2 inch overlap under the floor so I can rivet thru' the floor panels & NOT into the frame--don't want any holes down there !


Top
 Profile  
Reply with quote  
PostPosted: February 20, 2018, 9:33 am 
Offline
User avatar

Joined: September 22, 2005, 8:12 am
Posts: 1459
Location: 4AGE in S.E. Michigan
If you are concerned about drilling holes in the tubing you can always apply a sealer to the rivet, before inserting it. Just clean the head of the rivet gun in acetone after use and re-lube the head. When attaching the body panels, one should make a drill guide from 3/16 to ¼” thick stock. Carefully drill a couple different rivet hole pattern spacing’s, i.e. center to center distances, plus different edge offsets, into the drill guide. The guide will allow you to just drill one hole at the start of the pattern, with a single edge measurement, then use a Cleco to hold the guide in place. You can than drill several of holes following the guide as a pattern. You can repeat the process just by moving the guide forward, re-attaching the guide with clecos, and continue to drill the attaching holes with equal spacing and without the trouble of manually laying out each hole in the rivet pattern. I would also suggest that you invest in an air rivet gun. Will make life a lot easier. DaveW


Top
 Profile  
Reply with quote  
PostPosted: May 19, 2018, 11:09 am 
Offline
User avatar

Joined: December 17, 2010, 1:24 pm
Posts: 1286
Location: Gainesville, Mo.
(BUMP)

_________________
Mike - Read my story at http://twinlakesseven.blogspot.com/


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 35 posts ]  Go to page 1, 2, 3  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
POWERED_BY