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Learning how to build Lotus Seven replicas...together!
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 Post subject: MX-7 build!!
PostPosted: Mon Sep 02, 2013 11:21 pm 
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Location: Guadalajara, Mexico
No!! It's not an improved Mazda MX-5, but a MeXican 7 replica =).

Well, some background first. My first approach to the locost world was this article about a 100mpg Lotus replica.

http://www.treehugger.com/cars/man-builds-100-mpg-lotus-replica-that-runs-on-homebrewed-biodiesel.html

The builder of that interesting machine happened to be Jack =). Then I obviously looked for his Kinetic site, which sent me to this forum.

It's been a few years now about reading build logs(I specially like Nick's MGB one!), understanding (kind of..) tech concepts about suspensions, getting tips and tricks from all of you and thinking about what could be made in my place.

So in order to keep it simple and have bigger chances to finish it I choose a datsun donor. As you may guess it won't be that powerful, but 80-90hps should keep a light seven alive. From the datsun I plan to use the engine (J18 1800), the oem 5 speed transmission and the solid axle. Datsun are kind of narrow, then I'd like a book chassis, I just need to make some measurements on the axle length and myself, just to be sure I'll fit on it.

I already got spindles from a Nissan vanette, which have the same bolt patter as the datsun I got. Ah yes, I already got a running 83 Datsun Sakura for about USD $700, it may not sound like a great deal for a garbage can, but it's kind of difficult to find something cheaper around.

Now, my next tasks will be removing all working stuff from the car, keeping what I need, hopefully selling something I won't need from it and getting a build table to start some welding =)

A couple of pics from the donor...

Image

Image

Hope to post something else soon..... thank you all!!


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 Post subject: Re: MX-7 build!!
PostPosted: Tue Sep 03, 2013 10:50 am 
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Mhmh.... didn't work loading the images in my post above.. here's a second try


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 Post subject: Re: MX-7 build!!
PostPosted: Tue Sep 03, 2013 2:16 pm 
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blackfabian wrote:
Mhmh.... didn't work loading the images in my post above.. here's a second try


Man does that engine picture bring back some meories, my first cars were Datsun 1000's!
err B10's I think to you guys.

Good luck!


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 Post subject: Re: MX-7 build!!
PostPosted: Tue Sep 03, 2013 6:20 pm 
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Ditto and welcome. Nice choice for a donor.


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 Post subject: Re: MX-7 build!!
PostPosted: Sat Feb 15, 2014 3:29 pm 
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Location: Guadalajara, Mexico
Wow... time really flies.... =S

But, I finally have my build table done and engine out from the car. The only thing remaining in order to start with the frame is a decent saw for accurate cuts, I used a chop saw for the build table frame and I didn't like at all. I was thinking on using a miter saw and put and abrasive disc on it.... do you know of drawbacks for this setup? I'll for sure pay attention on not exceeding the disc RPMs.

Anyway... here's a picture from the build table and engine.


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 Post subject: Re: MX-7 build!!
PostPosted: Tue Mar 18, 2014 11:19 pm 
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Location: Guadalajara, Mexico
We just had a long weekend where I could spent many hours on the frame build... I'm really happy on how it came out =). Next I'll work on the rear section of the frame.. I already did some research on how to bend the rear top corners and found a procedure that seems easy enough to let a try.

Hope to post something else soon.

Fabian


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 Post subject: Re: MX-7 build!!
PostPosted: Wed Mar 19, 2014 1:56 am 
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Looking good so far. No turning back now.


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 Post subject: Re: MX-7 build!!
PostPosted: Wed Mar 19, 2014 6:47 am 
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nick47 wrote:
Looking good so far. No turning back now.

Yep, like he said... It's looking like a car already, keep going forward, you'll be driving before you know it!
:cheers:
JDK

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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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 Post subject: Re: MX-7 build!!
PostPosted: Mon Apr 14, 2014 10:36 pm 
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It took more than expected that bending thing(most difficult part so far...), but, it is done now along with some other pieces of tubes here and there. I think the frame is about 80% tack welded =).

On the sad side, I'm having some issues with my welds. I started tack welding the frame using flux core wire with pretty decent results, then I ran out of the flux wire and bought a CO2 bottle and solid wire, expecting my weld to be better. Unfortunately, for some reason I still don't understand, the welds using the solid wire and the CO2 are terrible, very porous =(. I already played with the CO2 flow rate and changed the gun tip for a new one without improving. So I'm starting to think there's something wrong with the machine =(. Do you guys have any tip I can try before getting the welder to the shop to check it?

Fabian.


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 Post subject: Re: MX-7 build!!
PostPosted: Mon Apr 14, 2014 11:28 pm 
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Location: Queen Creek, Arizona
Did you change the Polarity? Flux core should be running DC neg. When You change to solid you should go to DC Pos. You may also want to bump up your wire speed a little.

Walt


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 Post subject: Re: MX-7 build!!
PostPosted: Tue Apr 15, 2014 8:28 am 
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Fabin
You do not have enough gas flow!!! Here is areas to check; the tank regulator flow. The gas line for blockage and the gun valve, and the metering holes inside the nozzle just below the wire feed tip. You probably have weld spatter inside the nozzel area from the flux core, which is blocking the flow of CO2. Stop by your local welding supply shop and get some anti-spatter spray or jell for the nozzel to reduce the build up inside the nozzel area. You are off to great start :cheers: . Dave W


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 Post subject: Re: MX-7 build!!
PostPosted: Tue Apr 15, 2014 9:35 am 
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As Walt says, if it's running well with fluxed core then you need to change the polarity for Co2 welding.

Most these days have a switch and it's simple otherwise we can run through it with you and tell you how to change it over but will need a few of pictures of the welder's guts.


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 Post subject: Re: MX-7 build!!
PostPosted: Tue Apr 15, 2014 11:52 am 
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Location: worcester county, Massachsetts
yeah what they've said, RE:changing polarity. flux core needs the gun to be negative, MIG needs the workpiece to be negative. many of the smaller MIG/fluxcore welders have the cables attached to their respective contacts inside teh wire reel door near the wire feed mechanism. you should be able to see plainly which is which, they are generally marked pretty legibly. the several machjines I've poked around inside have been, anyway.

also, I see that great big opening to the outdoors around your workspace. pretty much any breeze will blow the shield gas away, so closing off the area to prevent breezes flwoing though is a good idea. when I weld in my garage, I can either have the big bay door open, or the side door, but not both, know what I'm sayin' ?

don't worry too much about those ratty MIG attemps, since they're only tacks. once you get down to the full welding you'll be flowing right over those anyway, remelting as you go

at this point though, until you get teh MIG weld quality sorted out, maybe weld on some scrap practice pieces.

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 Post subject: Re: MX-7 build!!
PostPosted: Tue Apr 15, 2014 9:25 pm 
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Location: Guadalajara, Mexico
Thanks all for your comments.

Walt, yes, I changed the polarity, but I'll try playing with the wire speed.

Dave, yeah I thought on the gas flow issue and I did try "cleaning" the 4 small nozzle holes with a needle. I can feel with my fingers some gas flowing when activating the gun, but being my first gas mig attempt I'm not sure if that flow level is enough. I'll try doing some extra cleaning.

Cheapracer, there was no switch, but it was just a couple of bolts thing =).

Robbovius, as you noticed it's mainly outdoors, I just have a cover to keep the sun away a bit. But, thinking that the rainy season is just a month and a half away I do need for sure closing the area to keep wind and rain away.

Again, thanks for your comments! I'll let you know how it goes.

Fabian


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 Post subject: Re: MX-7 build!!
PostPosted: Tue Apr 15, 2014 10:00 pm 
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Looking good so far. It's deff a gas issue. Just keep tinkering with it till you get that nice frying bacon sound.

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