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Learning how to build Lotus Seven replicas...together!
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PostPosted: Thu Feb 09, 2006 12:39 pm 
Hey guys!! Just joined this group after looking at web resources for the Locost roadsters.

I'm about 2 weeks into my first build here. Have had lots of experience with drivetrain swaps and custom offroad suspensions, so this is something that is both new and familiar to me.

My Locost chassis is a McSorley 442. I am using a Nissan 240sx as the donor and so am adapting the chassis for IRS. I am using an IRS setup similar to the Tiger Avon, but with suspension geometry measurements pulled from the uk locost site.

Engine will be a Nissan KA24DE 2.4L dohc 4 cylinder w/ 5 speed transmission. Stock hp for this engine is around 150hp. The rear IRS will be constructed using the Nissan 240sx hubs, halfshafts, and a 4.0:1 differential from the donor car. Rear WMS-WMS width measures out to approx 61.5", which will work well for fwd offset wheels.

Here are some early photos:

Basic chassis coming together:
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One choice of wheels I had.. they were free! But, it looks like i will be going with 4 lug hubs, so I cant use these.
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Next stage of the chassis construction.. IRS subframe. You can also see the nifty hub flanges that the 240sx uses. I will construct an upright that these will bolt to similar to the Tiger Avon design. Mine will also position the rear disc brake caliper though.
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Starting to look like a car chassis!
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Last night, I got almost the entire trans tunnel welded in. I'll post up some photos of that tonight.

A friend of mine is donating a set of Porsche 914 seats and seat adjustment rails for the project. They measure 18.5" wide at the bolster, so will work very will with the 19" width of the interior seating space.

One question I had for you all.. has anyone gone with a steering rack mounted aft of the front wheel centerline? The reason I'm asking is that the 240sx knuckles have the steering arms on the rear and the factory rack sits behind the front wheels. besides the positioning, is there any inherant disadvantage of going with this sort of rack positioning?


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PostPosted: Thu Feb 09, 2006 1:39 pm 
having the rack aft of the centerline isn't abnormal, its pretty common, I don't think theres much advantage either way, other then packaging. I was talking to Alex Pfeifer (battleversion) and he brought up something that I think that most of us neglect to take into account, Ackerman.
http://www.smithees-racetech.com.au/ackerman.html
This, might be something you want to take into consideration.


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PostPosted: Thu Feb 09, 2006 1:55 pm 
Good looking Dime.


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PostPosted: Thu Feb 09, 2006 2:06 pm 
I was reading those ackerman documents.. found some over on uk locost site. Very good info. Also looks to be something you can adjust later on if you build your rack mounts with that in mind.

Thanks for the feedback on the rack position though. I will probably end up using the 240sx rack, but I dislike the thought of putting power steering on the car. I may scrounge up a rack from a Datsun 240-280z.. they were decent manual units and I believe are aft mounted as well, so should work nicely.

The yellow car is my baby, a '72 datsun 510. It has a documented 39,000 original miles on the chassis. Unfortunately, the original engine was overheated terribly. So, it now has a 3.0L Nissan v6 under the hood. very quick little car and a real blast to drive. couple pics of it:

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PostPosted: Thu Feb 09, 2006 2:21 pm 
also be aware, shifting the rack position can effect bump steer as well, rack position is not ussually something that is made adjustable for this reason. You really need to sort this out before hand I think.


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PostPosted: Thu Feb 09, 2006 2:34 pm 
Oh absolutely... I'll go through all the standard setup to check for bumpsteer, etc when I position the rack. No biggie really.

If you think about it, vertical adjustment is done to eliminate bumpsteer. Horizontal (fore/aft) adjustment = ackerman adjustment. So, if you concentrate on one axis at a time, it isnt too bad.


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PostPosted: Thu Feb 09, 2006 2:39 pm 
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Joined: Wed Sep 21, 2005 6:09 pm
Posts: 253
Location: Laveen, AZ
Howdy! I think I saw your 510 in the trader recently, or something very like it. I'm in Phoenix, around South Mountain, if you ever need any help or just to BS about the build.

-Steve


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PostPosted: Thu Feb 09, 2006 6:25 pm 
Hi Sven!

Definitely wasnt my 510.. I've had mine for the last 8 years+. ;)

Yeah, we'll have to get together sometime to kick tires. I live way out on the east side (Power & Mckellips), so I'm a ways out. However, I work at 24th St and University, so I am just up the road from you most of the week.

My current dilemma on the project is the front wishbone construction. I scored about 20ft of 1.12"x.75" DOM tubing for just over $30 today at lunch... not bad at all!

Just as some background, I am thinking that I'll use poly bushings for the lower inners. The lower outer will be the 240sx balljoint. I can use a 7/8" right hand threaded TRE as the upper balljoint on the outer if needed... as I have the required taper reamer to do that. That leaves the inners on the upper a-arm, which I would like to use heims for, as it will give me some degree of castor adjustment as well as a nicer camber adjustment.

So... if I use heims on the inners, what size should they be? What size heims are typically used on locosts for front suspension arms?


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PostPosted: Thu Feb 09, 2006 7:03 pm 
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Joined: Mon Aug 15, 2005 10:13 pm
Posts: 7048
Location: Charleston, WV
I think most folks use 1/2" heims. Look at the sticky post at the top of the suspension forum for some diagrams on A arm construction. They are for use with S10 knuckles but it may give you some ideas.


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PostPosted: Thu Feb 09, 2006 7:08 pm 
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Joined: Wed Sep 21, 2005 6:09 pm
Posts: 253
Location: Laveen, AZ
I just scored a new job at Broadway/I10 (ish) in Tempe. I'll be off work all next week and start the new gig on the 20th.

I agree, upper inners will do well with heim joints for the reasons you said. I used 1/2" for mine with a 5/8" for the upper outer. Lower outer is a Toyota balljoint.

Making the control arms to suit the uprights is non-trivial and took me a very long time to get right. You're welcome to come and see. My plans for next week are to get the frame stripped down and painted with POR15 so I can get serious on final fitment and hopefully get the bugger running soon.

The 510 I mentioned is still in the trader, it's white so not muc like yours. I just fixated on the 6 cyl conversion:

http://adcache.collectorcartraderonline ... 909229.htm

-Steve


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PostPosted: Fri Feb 10, 2006 1:56 am 
A few update photos:

The trans tunnel turned out really nice!!
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A side profile of the trans tunnel. It is a very comfortable 10.25" off the floor of the car.
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Heres what I spent most of this evening working on. Got the spindles all cleaned up and ready for the a-arm fab work:
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Rather than use the cut down strut, I'm going to use a more elegant approach and completely fabricate a new upper balljoint mount to accept a Chevy 3/4 ton tie rod end. :)
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And a pic of the 510. :)
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PostPosted: Fri Feb 10, 2006 7:10 am 
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Joined: Wed Sep 21, 2005 6:09 pm
Posts: 253
Location: Laveen, AZ
datz510 wrote:
One question I had for you all.. has anyone gone with a steering rack mounted aft of the front wheel centerline? The reason I'm asking is that the 240sx knuckles have the steering arms on the rear and the factory rack sits behind the front wheels. besides the positioning, is there any inherant disadvantage of going with this sort of rack positioning?


I missed this question, sorry. I am using Toyota converted struts which are also rear steer. I used a mid 80's VW Golf rack, which is also rear steer, and had to cut it down by about 5". I wouldn't worry about a rear steer, assuming you take time to get the rack width correct and do a bunch of bumpsteer measurements to set the height you'll be golden. Here's my web page where I got through all that:

http://www.toyotus.com/gallery/Steering

-Steve


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PostPosted: Fri Feb 10, 2006 11:33 am 
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Joined: Tue Aug 16, 2005 10:29 am
Posts: 1064
Location: Alberta, Canada
Project looks great. Nice 510 - always liked those car especially with an engine swap


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PostPosted: Fri Feb 10, 2006 11:53 am 
Was talking with a coworker yesterday.. and he has a Porsche 914 steering rack he will give me (he has a ton of parts cars). I was looking at some photos and it appears that these racks are tiny and center input. Might make for an interesting linkage, but it will not require any cutting down. On the porsche side, I'll adapt the 240sx tie rod end outers, so that will take care of both the TRE and any width change all in one shot.

here is a pic of the Porsche rack.. it is an aft mounted unit as well, but could be flipped over easily to operate forward of the wheels, since it has a center input! It will make for a rather interesting steering linkage I think. The unit is a 3.1 turn lock to lock rack, but with the shorter 240sx knuckle arms, it may be closer to 2.5 turns when it is installed.

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PostPosted: Sun Feb 12, 2006 1:52 am 
Some update pics from tonight.. went and picked up quite a few parts for it..

Picked up:

Porsche seats, seat rails, rack & pinion, steering column, linkage, and tie rod ends, and the 240sx differential.

Also borrowed a KA24 block and pan to help with making mounts and stuff.

differential is a perfect fit. Just need to make some mounts for it:
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Up front, we have the Porsche rack and pinion.. This setup looks like it will work VERY well. The really nice thing about the porsche rack is that it has built in threaded mounting bolt holes, so there is no need to make mounts to hold the rack captive, you just bolt it on..
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Started work on the scuttle framing. Starting to take shape!
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The 914 seats are a perfect match for this chassis!!! Couldnt ask for a better fit:
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KA24 block and oilpan... now just need a tranny and I can start making mounts.
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