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Learning how to build Lotus Seven replicas...together!
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 Post subject: Re: sprite into locost
PostPosted: August 3, 2017, 5:14 pm 
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Joined: January 31, 2008, 5:34 pm
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Location: SW Wes Consin
It has been a while. Finally I have parts that prove this body can be made and maybe by me. These are all final except the baffi (mustache). They still need about a few hundred more hours of scribing, trimming, welding and planishing to be a body. It's a learning process, right. A few things worth learning: keep notes, make really good patterns and when they say shrink it is going to shrink, don't try for really big panels to save on welding. There are probably 100 other things but I don't always take notes.


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 Post subject: Re: sprite into locost
PostPosted: August 4, 2017, 10:22 am 
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Location: Carlsbad, California, USA
Hey, good on ya! Keep it up.

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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 Post subject: Re: sprite into locost
PostPosted: October 4, 2017, 7:48 am 
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We are Slotus!
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Yo- That is some seriously cool work. Amazing...
More pictures!
:cheers:
JD

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Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
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 Post subject: Re: sprite into locost
PostPosted: November 7, 2017, 7:24 pm 
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Location: SW Wes Consin
My monthly post. Figuring out how to join panels.

Some things I have learned about welding aluminum body panels:

First I started with OA. I had watched some Kent White videos and became convinced that old school was best. It may be but the parts take a lot of prep and I don’t have any way to wash off the flux making using it a big pain. And the flux tends to get all over and causes bare metal surfaces to corrode quickly. So after buying the whole Kent White kit and spending quite a few hours trying to master the art of OA, including a trip to MM where every one seemed to be using TIG, I decided to try TIG.

Figuring out the welder set-up was the first step. If you don’t know what the terms mean (I didn’t) the instruction book is worthless. Miller has some good instruction videos, although finding them is tricky. Go to youtube and search very specifically, “TIG welding thin sheet aluminum” worked. There are a lot of videos on this subject and many are of no use. Next, I sheared some .063 and .050 coupons for practice and had at it starting with a 1/16 tungsten and 1/16 1100 filer and the machine at 75A, 120 Hz. and AC balance at 75%. These settings worked but I backed off the AC frequency as the higher frequency gives better penetration. This also means you burn through a lot easier. I am now back at 90-100 Hz for the top bead and then back up to 120 for the back side fusion weld. This is working ok. I need more practice and then I will try the triangle waveform setting which is for thin material.

Please read this and tell me if it makes any sense.


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 Post subject: Re: sprite into locost
PostPosted: November 9, 2017, 4:31 pm 
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Location: Carlsbad, California, USA
I can't critique the aluminum TIG welding, but do wonder what the recommended process is for clearing off the oxy-acetylene flux?

I attended a class where it was done, and I remember the idea the instructor had was to cut off strips of the same material as your raw stock to use as filler rod. He felt it gave the best results for shaping and finishing. He did go on a little about the flux and how corrosive it was, but I think his process for cleaning it off was pretty simple.

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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 Post subject: Re: sprite into locost
PostPosted: November 9, 2017, 7:04 pm 
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Location: Duxbury, MA USA
Have you tried backing up your weld with a piece of stainless. Mostly it keeps the back of the weld clean as the gas envelopes the entire weld. It also can give a bit of support if you are too hot and the weld sags.

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 Post subject: Re: sprite into locost
PostPosted: November 10, 2017, 3:46 pm 
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Location: SW Wes Consin
It is a little curious (to me) but the panel gets a lot hotter when you gas weld it than when you TIG weld it. The TIG arch seems so concentrated that the overall panel doesn't seem to heat up as much. The result seems to be that the OA panel gets annealed and the TIG welded panel gets a distinct HAZ (heat affected zone) without over all annealing. The result is that TIGed joints tend to crack. This is why you turn the panel over and fusion weld the joint back. Watching the oxide layer get burned off by the TIG is pretty cool and when you flip the panel you get a kind off lumpy gray surface with a line across it. The line disappears and gets shiny when you fusion weld the back.

So far I've made some pretty good welds using TIG so stay tuned for when I graduate to big panels.

Lonnie: The recommended method for flux removal is to wash the panels in hot water right after welding. That doesn't work for me as my garage isn't plumbed and it is about 20° out. Also, as you are welding there is some splattering around of the dried flux which gets on everything. If I could work outside it might be ok.

The shearing off a piece of base material would be ok but I don't have anything but hand shears and snips and 1100 rod is easily available here.


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 Post subject: Re: sprite into locost
PostPosted: December 31, 2017, 12:59 pm 
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Location: SW Wes Consin
The temp here has dropped to a point where heating my shop is economically unwise so I am putting off welding panels in favor of a little chassis design work. Yes, I know I am going about this backwards. I have been collecting fotos of bare chassis from the web. Very interesting,to me, are the TZ Alfas for their dash level bulkhead design and the Lotus Elan with it's Spitfire like cross member. So I wonder, has any one tried to integrate either of theses designs in a Locost ?? The Alfa seems to have eliminated the dash bulkhead in favor of a large section tube pushed way up behind the cylinder head connected with lots of trelliswork. The Elan cross member strikes me as easier to build than the usual U brackets hung on 1" tubes. Is there something I am missing here ?


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 Post subject: Re: sprite into locost
PostPosted: December 31, 2017, 2:28 pm 
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Location: Cornholio OR "Where the magic happens"
Everything is a compromise.

The Alfa with the big beam above means the car has to be built around that beam and it raises the center of gravity.

On the opposite end of the spectrum is the Lotus it sacrifices (driver safety) all other concerns for a minimalist super rigid spine minimizing polar moments and maximizing a low center of gravity and light weight.

You have to decide what your priorities are and design around them.

You can't have a super light simple chassis AND have a top fuel cocoon cage around the driver.

A Locost is supposed to be an open cockpit vehicle that is part of the allure, it is like a motorcycle with 4 wheels.

A simple cage will offer more in structural rigidity than occupant protection.
It provides a "feel good" for the driver and will provide some low speed protection but has little high speed capabilities or protection from ingress of foreign objects.

I would stick with a "Book" style design to stay within the spirit of the Seven concept.
Anything too far from that detracts from the finished product and may not offer much more in the way of protection.
The book frames combine the Spine concept of the Lotus with a perimeter "trellis" which provides the cockpit and body mounting (missing from the Lotus) as well as structural rigidity missing in the Seven's lightened spine.
It's a blend of both a perimeter and a spine design.

If you are building a track car or a hill climber you might want something very different as the driver may want more protection.
Governing bodies also shape the chassis design and any cage requirements.

For me an open cockpit and light weight design is best for normal driving and autocross.
For a track car or a hill climber a simple cage is inadequate the design priority then becomes a cage first with suspension and motor mounts.

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 Post subject: Re: sprite into locost
PostPosted: December 31, 2017, 4:03 pm 
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Location: Carlsbad, California, USA
Yes, all design is compromise. The two chassis example you posted are orders of magnitude different in term of actually designing and fabricating them. For a person doing their first chassis, the Alfa example is a big, big challenge.

A Book (or McSorely, or Haynes, or some other similar design) has some elements of each example. It has the benefit of being simple, and there is a ton of examples where it has been scaled in various ways. It has been adapted to accept just about any kind of front suspension, or rear suspension, or combination of front and rear suspension that one could imagine. So, it is a well-known and tested architecture. Plus, you can buy a number of ready made parts from Jack at Kinetic or other suppliers. It's pretty hard to beat for amateurs.

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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 Post subject: Re: sprite into locost
PostPosted: January 1, 2018, 1:41 pm 
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Lonnie and all,
Actually I'm thinking about something with a lot fewer diagonals than that foto would suggest. That is, swap some weight for complexity. What I like about the TZ pushing the dash hoop way up next to the bottom of the foot well is that this makes adding doors possible.

I long ago gave up on a standard frame when I decided to use the standard Sprite rear axle which is too narrow and pushes the seat forward. Because the standard lower frame rails start narrowing at the cowl this design pretty much eliminates the foot box. I'll post a sketch when I get to my work station.

Regarding the Elan front end. It sure looks to me like a Spitfire the parts for which are pretty available. Maybe just bolt on. I was just wondering if anybody on this site had ?

Tim


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 Post subject: Re: sprite into locost
PostPosted: January 2, 2018, 12:35 am 
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Location: Cornholio OR "Where the magic happens"
You can use high offset wheels for more width?

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 Post subject: Re: sprite into locost
PostPosted: January 2, 2018, 11:16 am 
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Joined: December 29, 2007, 10:41 pm
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Location: Vancouver, BC
Tim,
Have a look at the Series 4 Lotus 7 chassis, they used a front cross member similar to the Elan (though the 7 used Europa a-arms). The Elan arms are unique Lotus bits, but as you would be building your own you could use the Spit bits though the lower wishbone is rather wide at the chassis end.

Image


Rod


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 Post subject: Re: sprite into locost
PostPosted: January 6, 2018, 12:36 pm 
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Location: SW Wes Consin
Bent
Sprite axles are not known for their strength so offsets might not be so good.

Rod
Once again you have a foto of what I am thinking about, thanks. I seem to recall that you once posted a foto of a space frame that had a B pillar pushed forward. This, of course, makes a usable door possible which is not possible with either a 7 or a Sprite.

Tim


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 Post subject: Re: sprite into locost
PostPosted: January 6, 2018, 8:59 pm 
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You can always get double bearing rear hubs if you have any issues. Biggest downside will be the loss of the standard e-brake - would also require going to rear disk brakes to keep an emergency brake.

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