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 Post subject: Re: sprite into locost
PostPosted: December 13, 2020, 3:55 pm 
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Thanks for the kind words guys. I 'll back fill the missing fotos and continue.


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 Post subject: Re: sprite into locost
PostPosted: December 13, 2020, 4:36 pm 
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6" of snow yesterday so i"m spending a quiet afternoon recovering from yesterday's shoveling. I am reading the Sterling Moss book and he is bad mouthing the Coopers of the day. Although there were periods when Coopers were quite successful, including with him driving. I mention this because a rework of my chassis, post body, will be in order and those Coopers were really simple with a minimum of odd weld joints. Heavy but simple and not so fragile as many space frames are. A friend who used to race 7s referred to them as flexi fliers. This leaves me wondering how many people have tested their frames for torsion and is all that complication worth the bother?


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 Post subject: Re: sprite into locost
PostPosted: December 14, 2020, 1:41 am 
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That may have been in the early days so Lotus or Caterham certainly did engineering analysis.
I'm sure they bent up a few and had plenty of opportunity to move stuff around a bit.

As to the Flexi Flyer comment, racers will be racers....
How do you beat another, build a lighter car! They probably built them with rice paper for racing, tell the driver to not touch anything or it would rip the wheel off.

To the uninformed it looks like they are patio furniture but the square tube is actually more rigid than round of the same size.
What give the car it's rigidity is the tunnel which behaves like a 3D X brace.
I don't think the chassis would last very long if it was flexing moderately. It would work harden and crack.

It may very well be that they are overbuilt @16ga and there are ways to use different weights and make a super light one.
The material outlay is small it would not surprise me that someone had done this as a throw away car for one special race or hill climb.

I think there have been quite a few who have run FEA?

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 Post subject: Re: sprite into locost
PostPosted: December 19, 2020, 5:45 pm 
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Has anyone mentioned a get together for maybe mid summer. I sure hope we will be able to travel by then.


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 Post subject: wheels
PostPosted: August 12, 2021, 6:40 pm 
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It has been a long time since I last posted. For that i apologize. It isn't that I haven't been doing anything, just no forward progress. I am still on the trail of how to TIG aluminum. The current potential solution is to use 50/50 mix Ar and He. As I haven't yet gotten delivery from my local welding supplier I'm twiddeling my thumbs and thinking about the project.

If you have waisted your time and read this thread you would realize that one of my ideas was to build a Locost out of parts from the rusted out hulk of an A-H Sprite (which I got cheap). This has resulted in many deviations from the standard build plan. One of the challenges has been how to build the front suspension. As it happens this has been done before, although I'm not convinced about the design. It still uses a kingpin. This is the sort of thing that keeps me up when the welding is not going forward. My latest scheme is to use the front end parts out of a Spitfire. This, of course, is the route taken by many early kit builders. Look at the uprights on most any pre big V8 race car and you will find the Spitfire upright.

Domandi:
1. So why not graft a Spitfire front end on the front of my Sprite parts? The first question is: using what wheels? I'd like to use the Sprite wheels which fit the rear axle and I have a number of. Will they bolt up to the Spitfire front end?
2. Do any of you who have spent time with the Spit bits have any sort advice ? No laughter please. Snickering is OK.


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 Post subject: Re: wheels
PostPosted: August 12, 2021, 7:01 pm 
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1) No, Sprite and Spitfire wheels have different bolt circles, Sprite is 4", and Spitfire is 3.75" Center holes may be different as well but that depends somewhat on what wheel you're using as hubcentric wasn't common then.

2) I'd be inclined to find GT6 front suspension/brakes. Arms are interchangeable but the GT6 got larger brakes due to the increased horsepower and weight over the Spitfire.

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 Post subject: Re: wheels
PostPosted: August 12, 2021, 7:17 pm 
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Dave Bean sells (or did sell) front hubs for the Stanpart uprights in various PCD. I had a set brought in for a customers Lotus 7 (back when I was selling car parts) with a 4" PCD to match the Spridget rear axle in his car. There might be another way to get around it though, there's a guy on GRM that had his Europa front hubs re-machined to a 100mm PCD using a wheel stud with a larger shank, so no welding was required to fill the existing holes. I have a bunch of spare hubs if you want a sacrificial sample to machine up, though I am north of the 49th, so shipping might be expensive.

As for the GT6 uprights and brakes, I wouldn't bother with them. The Spitfire sized calipers should be just fine with a small car like an aluminum bodied Ferrari-esque Spridget based automobile. The 16P calipers on the GT6 are heavy. If you want to go bigger with brakes, Cateringvans still use the Stanpart upright, so big brake kits are available.

You might also try Canley Classics, they do a bunch of trick bits for the Spitfire based suspension.


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 Post subject: Re: sprite into locost
PostPosted: August 27, 2021, 12:06 pm 
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I wouldn't necessarily let the kingpin design discourage you from using it. It is compact, parts are available, and it is one less thing you would have to engineer. While there are drawbacks, I like being able to decouple the steering axis from the points where the arms pivot.

The biggest downfall to the Spridget design is the fulcrum pin. If you didn't want to reuse stock arms, you are left with either making two threaded bungs (probably a lathe job since at least one of the threads is a non-standard size) and carefully aligning and welding them to your arm or eliminating the threaded fulcrum pin design and using a straight pin with bushings.

Another option would be to follow in Craig Chima's footsteps and develop a system that uses spherical bearings but retains the stock swivel axle: http://britishracecar.com/ChuckPitt-Spr ... et-CE2.jpg

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 Post subject: Re: sprite into locost
PostPosted: September 5, 2021, 1:52 pm 
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Thanks guys. I wonder just what sort of cast iron Triumph was using. It makes quite a difference in welding. I'd go for Canley Classics but they don't seem to be stocking hubs any more. Guess I should drop them an email.

Regarding the Triumph front end I think it is great for a light car. The heavy parts are the calipers and the hubs. No wonder they made it into so many race cars.


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 Post subject: Re: sprite into locost
PostPosted: September 9, 2021, 4:19 pm 
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This is a pic of what I am thinking about for a front suspension.

/Users/timfreeman/Desktop/DSC01422.JPG

The problem with it is the axis of the lower swing arm pivot and the upper swing arm pivot and the upper and lower king pin joints have to all be parallel or the king pin will bind as the suspension moves up and down. It seems to me the Triumphs use of a ball joint on the top would relieve some of this binding. Although I see there are some trick parts to put a ball at the bottom as well. Canley Classics could solve these problems but they don't seem too interested.

Any clarity that can be provided is alway appreciated.


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 Post subject: Re: sprite into locost
PostPosted: September 9, 2021, 4:27 pm 
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Hmm that didn't work

Try this


You do not have the required permissions to view the files attached to this post.


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 Post subject: Re: sprite into locost
PostPosted: September 9, 2021, 5:25 pm 
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The trunion is very close to the rotor as-is plus ensuring the method of fastening a spherical so it does not loosen can be difficult.

Consider the using the trunion but fit the U brkt with a 3 inch, 3/4, coarse male threaded rod into a female threaded LCA with a grease fitting and don't use a jam nut. Use a standard UBJ. The threads will be a wear point to design for and check periodically but it will eliminate the bind on the trunion. FWIW, it just occurred to me. I've not seen it done.

You could also try tube within a bushed tube and pinned inboard with thrust washers for less weight. :cheers:

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 Post subject: Re: sprite into locost
PostPosted: September 9, 2021, 10:54 pm 
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vroom wrote:
The problem with it is the axis of the lower swing arm pivot and the upper swing arm pivot and the upper and lower king pin joints have to all be parallel or the king pin will bind as the suspension moves up and down.


The rubber bushings in the Spridget upper trunnion allow for some misalignment. I'd keep something like this rather than rigid mounting both the top and bottom

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 Post subject: Re: sprite into locost
PostPosted: September 14, 2021, 7:14 am 
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vroom wrote:
Hmm that didn't work

Try this

Are you asking for feedback on this design? Looks like a production birkin frame and arms.
Well thought out though the geo must have a very long vsa or very short coilovers so camber gain and roll center stability may not be as good as they could be. Not crazy about the single shear coilover mount and semi-floating antiroll bar mount but they did add lightness.

Could attach the anti roll bar to the uca or even make the bar integral to the uca for less weight and a cleaner suspension but it would lose caster in bump from the forward pull of the ubj by the bar. Better to have the uca integral bar behind the axle cl to add caster in bump or have a uca separate that doesn't locate the ubj as shown.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12


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 Post subject: Re: sprite into locost
PostPosted: September 14, 2021, 10:14 am 
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Miatav8,MstrASE,A&P,F wrote:
vroom wrote:
Hmm that didn't work

Try this

Are you asking for feedback on this design? Looks like a production birkin frame and arms.
Well thought out though the geo must have a very long vsa or very short coilovers so camber gain and roll center stability may not be as good as they could be. Not crazy about the single shear coilover mount and semi-floating antiroll bar mount but they did add lightness.

Just adding a single bolt all the way thru the UCAs and upper shock mount with spacers would have added some shear strength to the shock. A simple solution. Most of the new Mustang II control arms that eliminate the front strut rod use this method.

Thom

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