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 Post subject: Re: sprite into locost
PostPosted: September 14, 2021, 1:17 pm 
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Location: Vancouver, BC
Quote:
Looks like a production birkin frame and arms.


That's a shot of a Westfield XI chassis. The Lotus chassis was very similar in regards to the upper shock and arm mount, the shock being in single shear and the arm being in double. It worked just fine from 1957 through to when Caterham changed things slightly in I think the late 90's. In this pic you can just see the top of the shock:
Image

In regards to the Stanpart (spitfire, herald, elan, etc) uprights, you can either weld on a new lower stub to remove the trunnion (done quite often on single seaters), order the newer Caterham uprights, or find some acme nuts (rh and lh thread) that will thread onto the upright. All options would use a spherical bearing. I had a pair of uprights machined to remove the acme threads (root diameter is roughly 5/8") and re-threaded to take a UNF nut, but I'm not sure if they would stand up the roads around here.

Edit: Found the pics of the modified upright:

Image

Image


Last edited by cs3tcr on September 15, 2021, 3:15 pm, edited 1 time in total.

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 Post subject: Re: sprite into locost
PostPosted: September 15, 2021, 1:03 pm 
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Location: SW Wes Consin
Sorry for all the confusion. The foto I posted was for a Westfield 11 and it is designed to use the Sprite upright. This would be alright but I think it requires the upper and lower A arm pivots to be in parallel so no change in caster occurs or binding might occur. I think this is the reason for rubber bushings. I hope this makes sense.

I believe the Triumph upright has the same problem except that it has a ball joint on top and two longish arms on the A arm which might allow some slight twisting to alleviate binding. I think this is how this works. I 'll build front quarter to try it out.

I plan on using the solid (simple and I have one) Sprite axle. To solve the wheel bolt circle problem I'm having the Triumph hubs modified to match the Sprite wheel bolt circle 4x4".


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 Post subject: Re: sprite into locost
PostPosted: September 16, 2021, 11:05 am 
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CS3 I'm not sure why I would modify the Spit uprights ? Your foto looks pretty like my existing arrangement.


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 Post subject: Re: sprite into locost
PostPosted: September 16, 2021, 11:25 am 
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Modifying the upright allows for a spherical bearing at the bottom, meaning no more trunnion. It was common mod for single seaters, and Caterham has since gone to a spherical bearing at the bottom. It allows for caster adjustment, to adjust caster with the trunnion meant modifying the chassis pick-up points.


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 Post subject: Re: sprite into locost
PostPosted: September 16, 2021, 2:36 pm 
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Interesting. I'll try that when I find my fixed caster method doesn't work. My next problem is that I have the Spitfire hubs modified for the Sprite PCD but my calipers fit into the wheels by -.06". I could easily grind an eighth inch off the high spots on the wheels. But, I wonder how much clearance is enough?


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 Post subject: Re: sprite into locost
PostPosted: September 16, 2021, 3:45 pm 
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vroom wrote:
my calipers fit into the wheels by -.06". I could easily grind an eighth inch off the high spots on the wheels. But, I wonder how much clearance is enough?


A recommended minimum is 0.125" caliper to wheel. Is 0.06" to the wheel hub flange/spokes? Is it also a floating caliper with consideration for pad wear?

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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 17, 2021, 12:38 pm 
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Thanks! It's a fixed caliper so it should be simple.


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 Post subject: Re: sprite into locost
PostPosted: September 22, 2021, 4:11 pm 
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cs3
Sitting here waiting for my electrolysis set up to peel the grunge off some Triumph parts and I started to think how nice it would be to get some light weight replacement calipers. Being as you seem to know a lot about Triumph up rights I thought you might know of some Wilwood calipers that might fit.

Well back to the grunge.

vroom


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 Post subject: Re: sprite into locost
PostPosted: September 23, 2021, 6:56 am 
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Location: Chesapeake Va.
Vroom

I am not as well versed on Spitfire uprights as those compared to the Triumph Tr6. Though they appear similar in design. There are articles in Triumph Experience on converting the heavy Tr calipers to those of the Toyota 4 pot caliper off the pickup. These are an almost direct bolt on, using the correct hardware and some trimming of the back splash, to the original calipers. If the Spitfire uses 16P calipers then these should work.

Here is a link to read if you are interested. http://www.tiggersavage.com/tr6_brake_install.htm

Red


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 Post subject: Re: sprite into locost
PostPosted: September 23, 2021, 7:33 am 
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A great improvement but heavier, especially if also going to vented rotors. If you don't have a big enough lathe for the vented rotor, machinists for hire sometimes don't want the liability of modifying brake parts.

One downside to lightweight, aftermarket racing calipers is that they do not always have dust seals like oem calipers so seal wear/cutting and piston wear can be an issue if used on normal roads.

Why not try the stock system first? You may find it completely satisfactory. It is probably the most cost effective and timely process.

_________________
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 23, 2021, 9:53 am 
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Location: Vancouver, BC
Vroom,
To be honest, I've never really looked into lighter calipers, the stock ones have worked well for my builds. If you do want something lighter, you can look at the Caterham options, but doing some quick searching the usual answer for improved braking is different pads (I know that doesn't make it lighter, but it does make things better).

Reddragon,
The Spitfire uprights use a 14P caliper and has the caliper mount integral with the upright. But, if the uprights were of the Herald type, you can get caliper brackets for GT6/Lotus Elan +2 and use the Toyota caliper, as that bracket is set up to use the 16P/PB caliper like the TR6. You do need to find the "metric" caliper mounting bolts though (Metric shank, imperial threads).

Miatav8,
I agree with trying the stock system first, the brakes do work well for small light cars.


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 Post subject: Re: sprite into locost
PostPosted: September 24, 2021, 8:01 am 
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Joined: May 19, 2016, 8:46 am
Posts: 57
Location: Chesapeake Va.
cs3tcr

Thank you for that bit of information. I mainly work with Tr-4s and Tr6s. Have just made the Toyota caliper conversion to my Tr-4. For future reference the (Metric shank, imperial threads) can be purchased from Moss Motors using part # 320-215. These are from 1972-1976 Tr-6 according to their catalog.

Since you have some knowledge on these uprights, do you know the weight of the Spitfire compared to the to the Tr-6? In a street application a little more weight should not matter, but I am thinking of extra strength of the upright itself.

Also I didn't see where Vroom mentioned the bolt pattern he was striving for. Tr-4 and Tr-6 are 4", where Spitfire and Tr-7s are 3.75".

Red


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 Post subject: Re: sprite into locost
PostPosted: September 24, 2021, 9:04 am 
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It may not matter to you or me, but a 5-6 lb increase in unsprung weight is significant in such a light car. More so on rough roads than on a smooth track. It's not about speed.

_________________
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 24, 2021, 9:55 am 
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Location: Vancouver, BC
Red,
Off the top of my head, I don't know the weight difference. I have a bunch of Spitfire and Herald uprights in the garage, but they're buried at the moment. I'll see if I can find at least one of them when I'm in the garage this weekend.

Also, in reference to the bolt patterns, TR2 through 6 had a 4 1/2" PCD.


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 Post subject: Re: sprite into locost
PostPosted: September 24, 2021, 12:17 pm 
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Location: SW Wes Consin
I have modified the hubs for a 4"PCD Sprite wheel. Regarding the calipers I guess if it ain't broke.

Thanks all.
Vroom


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