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Learning how to build Lotus Seven replicas...together!
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 Post subject: Re: Locost Race Car
PostPosted: January 9, 2012, 10:02 pm 
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Joined: April 11, 2010, 2:27 pm
Posts: 23
More pictures.


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 Post subject: Re: Locost Race Car
PostPosted: January 9, 2012, 10:19 pm 
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And some more. If you notice (I didn't) the lower front a-arms are rather wide out at the wheel. When I went to run it down the street, it wouldn't turn very much before the rim hit the arm. After making new arms, it turns great now!


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 Post subject: Re: Locost Race Car
PostPosted: January 9, 2012, 11:17 pm 
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Hassle,

It's easier to use that LSD rather than something else because your stub axles and main axles fit without any fabrication. The biggest hassle is creating the housing to contain the lube for the LSD. I used a LSD from an '86 RX-7 non-turbo because I could get one cheap and the '93 Miata main axles matched the RX-7 stub axles. I did have to weld up some of the oil grooves in the stub axles because they extended out past the oil seals I had installed in both ends of the LSD. I had a machine shop machine the welds in the stub axles back to the original axle OD. I also had him machine grooves in the LSD assembly to accept the stub axle seals. Most of my inspiration came from Blue Devil's build thread here http://locostusa.com/forums/viewtopic.php?f=36&t=4970&start=165.

You need to take the assembly out of the rear end housing and remove the ring gear. Then make the LSD housing. I found a piece of 4" schedule 10 steel pipe was a very close close fit. On one end I welded a 1/8" steel cap with a hole in it sized to fit over the end of the LSD and a ring around the other end. The ring is sized the same as the ring gear flange. The machine shop machined holes in the ring to match the flange. He also machined the sprocket to fit over the LSD cover and the holes to match the flange also. I used Permatex gasket maker to seal both ends of the cover. Unfortunately, I have a very slow leak at the cover's flange. I would try to find a different sealant, if I were you.


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 Post subject: Re: Locost Race Car
PostPosted: January 10, 2012, 9:51 pm 
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Posts: 378
Looks like your using a jackshaft to meet the offset of the diff from the countershaft sprocket,those short chains will need to be replaced often.


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 Post subject: Re: Locost Race Car
PostPosted: January 10, 2012, 10:07 pm 
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L8 - It was either get custom axles made (expensive) or use a jackshaft. If I need to replace the chains every so often, that's OK. I did research this issue and I believe the chains won't have to be replaced nearly as often as some believe. I'll find out.

Hassle - I'm in southern Orange County.


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 Post subject: Re: Locost Race Car
PostPosted: January 11, 2012, 6:28 pm 
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Understand completely,the chain around the big diff sprocket will likely last at least twice as long as the bugger going around the 2 counter sprockets as all that sharp turning really impacts longevity.


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 Post subject: Re: Locost Race Car
PostPosted: January 11, 2012, 9:20 pm 
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Joined: February 5, 2010, 12:48 am
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Location: San Diego
Thanks for the responses. I'm now hooked on the idea of making one of these. :D


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 Post subject: Re: Locost Race Car
PostPosted: January 12, 2012, 12:31 am 
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Location: san francisco bay area
Beautiful, really it is but (of course there's a but) I'm a little concerned about the front hoop, it sure seems to have a lot of dynamic loads put into it especially from the shocks.
Add in the load from the front upper CA mounts going into the Y bar being applied dead center at yet another bend and well. .. I'd sure hate to see it fail on you.
Probably nothing to worry about though, I tend to be overcautious when it comes to such things (No it doesn't need a 3x safety factor Jack!!!!! :roll: ).

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 Post subject: Re: Locost Race Car
PostPosted: January 13, 2012, 12:08 pm 
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oldejack wrote:
I'm a little concerned about the front hoop,


Yeah if it was mine I'd probably throw in a couple of 3/4" brace tubes as such ...


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 Post subject: Re: Locost Race Car
PostPosted: January 13, 2012, 12:26 pm 
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cheapracer wrote:
oldejack wrote:
I'm a little concerned about the front hoop,


Yeah if it was mine I'd probably throw in a couple of 3/4" brace tubes as such ...


There? ...or angle farther back and connect where the next vertical tube is?


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 Post subject: Re: Locost Race Car
PostPosted: January 13, 2012, 8:45 pm 
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Thanks guys. I assume you are referring to loads imposed on the hoop during a roll-over. While the angled brace tubes are a good idea, there isn't any available space to run them. There may be room for a gusset type brace to the runners from the main roll hoop and then to the chassis, but that's about it. This pic of the steering wheel and shift lever will give you an idea of how tight everything is. However, the front hoop is not a contact point in the event of a roll-over. If you draw a line from the top of the roll hoop, the front of the foot box is the second contact point. The front roll hoop is several inches below that line.

I should have made the cockpit bigger and the front of the chassis longer. While I fit in it snugly (I'm 5' 5"), anyone bigger than me won't. Oh well, these are the things you learn when you do something for the first time.


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 Post subject: Re: Locost Race Car
PostPosted: January 13, 2012, 10:17 pm 
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Location: san francisco bay area
I was looking at the force application shown by the blue arrows and possibly putting in another tube on each side where the red line is.


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 Post subject: Re: Locost Race Car
PostPosted: January 14, 2012, 10:48 am 
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Have you driven the car yet Ric?

It may not be ideal (nothing is) but that center brace in the front is probably enough to keep the leg hoop in place. People put their front Locost shocks in the middle of a 1"x1"x0.065" piece of tubing and it seems to survive fine.

PS I like the steering wheel idea. I'm going to have to try that someday.

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 Post subject: Re: Locost Race Car
PostPosted: January 14, 2012, 9:19 pm 
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I've putted down the street a couple of times but that's it. I don't think the neighbors would appreciate a 10,000 rpm blast around the block. I'm taking it to an autocross practice at Cal. Speedway tomorrow to begin testing.

When I designed the car, I didn't take into account that most reasonable sized trailers are no more than 60" wide. The outside width of the car is 65". I borrowed a friend's trailer for the weekend. It has been a pain setting up the car on a 60" trailer for transport. I guess the most frustrating thing has been spending half the day trying to get a new electric winch to work. I finally gave up on it (I think it's a bad controller) and fitted a manual winch instead. While it is far from ideal, it will allow me to go to the event tomorrow and I'll get the electric winch figured out later.

I've actually toyed with the idea of finding an old box truck or ? to use for transporting the car. It would also allow the car to be stored outside of the garage and free up a lot of space. If anyone has any suggestions for something like this, please let me know. Any suggestions on where to look for something like this is greatly appreciated.


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 Post subject: Re: Locost Race Car
PostPosted: January 15, 2012, 8:14 pm 
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Well, everything went well today at the autocross. Everything worked like it should, except for the brake pedal. It cracked after a few runs. I found a guy with a welder in the pits and fixed it but it broke again within a couple of runs. So that ended my day. That's what I get for using a cheap cast pedal. It's easy to make a sturdier replacement.

Overall I'm happy. Nothing major broke and the car is blindingly quick in acceleration. However, I learned that I REALLY need some better tires. I'm using some very old NT-01's from my Miata and they don't like to heat up with an 800# car. It really couldn't accelerate in a corner until it was pointed somewhat straight or the back end would come around. I'll find some formula car take-offs and see how much of an improvement there is.


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