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Learning how to build Lotus Seven replicas...together!
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PostPosted: April 16, 2018, 6:07 am 
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Joined: March 15, 2018, 6:03 am
Posts: 33
Hi Guys
With thanks for the help I've had here, and on other pages, I would like to seek further advice.
I am currently living in Thailand and trying to tackle a project of this nature seems not too easy, with little local support for, or understanding of, such weird activity...

My biggest problem to date is sourcing uprights/knuckles/kingpins - none of the knuckles commonly used in the West are available here, and I don’t feel too confident about fabricating my own... e.g. where to actually start on the design...?

However I have come across a number of modern knuckles which all utilise the MacPherson strut principle so my idea is this: remove the strut, and perhaps the upper inch or so of the knuckle, and drill the casting to take a normal ball-joint. As all these cars utilise FWD I will also have to find a way to seal the rear side of the knuckle.
Attachment:
knuckle-01.jpg
knuckle-01.jpg [ 56.23 KiB | Viewed 250 times ]

This might not be too practical but let me ask two questions:
1. Is this idea too stupid to be believed...?
2. Has anybody else tried anything of this nature...?

Many thanks, Mangpong.
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PostPosted: April 16, 2018, 7:06 am 
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Joined: June 5, 2016, 7:03 am
Posts: 179
Location: ontario
[quote="MangPong"]Hi Guys
With thanks for the help I've had here, and on other pages, I would like to seek further advice.

I don't think that anything we do to build these cars at home can be called «stupid». Rather I would use: unpractical or too expensive as qualifiers. Here again I can only tell you what I have done with my two builds, which is not necessarily the best course..
In both cases I have worked from a «donor» vehicle; i.e I bought these cars for «parts». The first one was a Ford Aerostar van from a neighbour. It was not the best choice but it was there and cheap. With my neighbour's help I torn down the mechanical components of the vehicle, including all suspension, steering and brake systems. For the second build I went the same way (a 1965 GM Corvair). Some of the donor components needed to be fixed or remanufactured however, and there I found that the core parts were often needed to get new ones. The advantage of using parts from a donor vehicle is that they are designed to fit together . This leaves you with a simpler job to build a chassis that will receive these parts. Your best course of action would be to buy a small rear wheel drive car from a scrap yard or a neighbour, tear it down to get what you need . (alternatively ask the scrap yard to tear a car down for you). For new components, in North America we would also rely on after market part retailers or ebay. I hope this helps. :)


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PostPosted: April 16, 2018, 7:52 am 
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Joined: September 22, 2005, 8:12 am
Posts: 1437
Location: 4AGE in S.E. Michigan
MangPong
There are several builders here who have modified strut type knuckles, with good results. Typically the upper section is modified like your photo if using rod ends or they add an extension that allows a ball joint to be used. Once you have determined the basics of your front suspension, caster, camber, KPI, and scrub radius, that you want, you start looking for the knuckle, or if you already have a knuckle, then work backwards to see what parameters you can best incorporate into the up-right.
Just like everything here, be ready to make a few compromises. Most of the knuckles will for a FWD system and designed to reduce torque steer. To get a good scrub radius will require an inboard upper B/J extension or off set wheels. DaveW


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PostPosted: April 16, 2018, 10:25 am 
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Joined: July 17, 2008, 9:11 am
Posts: 4516
Location: West Chicago,IL
There are several ways to adapt a McPherson strut knuckle to upper/lower control arms. Since the upper joint "generally" sees less force, the use of an appropriately sized rod end joint might be applicable. I did this on the front end of my build by building an adapter which bolted into the holes previously used for attaching the McPherson strut. See my photo below. It's not very pretty. But it is functional.

I eyeballed the upper mount of the McPherson and put the rod end along that line, keeping the scrub radius that Davew mentioned under control. Of course, that only works if you use the original wheel offset.

We are a bunch of inventors here. There is no one solution.


Attachments:
adapter.JPG
adapter.JPG [ 61.27 KiB | Viewed 224 times ]

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PostPosted: April 16, 2018, 1:23 pm 
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Joined: March 15, 2018, 6:03 am
Posts: 33
My gosh, you guys (collectively and individually) are magic - good ideas and rapid responses...

First, I am pleased that my (possibly silly) idea hasn’t phased you - I post them here because I'd rather be shot down in flames here than end up in a ditch beside the road...

Secondly, it’s just nice to be able to discuss... to just throw out ideas... None of my friends, family, neighbours has any understanding of what I'm trying to do... and usually ask (if they ask anything), ‘Why’’’?’ Do we all have this problem...? lol.

phil
I'm sure the ‘donor’ idea is good - however, in this socio/economic culture there is no rubbish. Old cars run, usually with poor maintenance, until they just stop... and even then, if you offer to take the wreck away for them, they will expect payment - perhaps 10x what it might make in the West. Well over $2,000,,,!
Secondly, I am aiming for a rear-mounted motorcycle engine/transmission unit, which hopefully will be the ‘donor’, but it won’t help the front end. All I would probably take from a donor car would be uprights, brakes, and steering.
I've spent the past few weeks touring the area for scrapyards, such as they are... and they are rather different to ‘back home’ when you trawl around various models of cars to see what’s been left. Here we have breaker’s yards, where they break out everything they think has value and they hang the bits for you to see... And they specialise: one place will have engines/gearboxes; another rear axles; another suspensions, and racks... indeed there are racks and racks of racks... It was amusingly eyeopening.

daveW
Thanks for the confirmation of what others have done with MacPherson struts - very gratifying to know others have already tried it, and not ditched the idea. Until now I've been working on the suspension design, around compromise dimensions I've found online or have guessed at, and have now had a bit of a shock that the uprights that many of you guys have been using are now in very short supply. The only offer I've had hear for anything resembling what we all like is from Isuzu, and is very big and heavy... more than the Miata... and the Miata is only available here as a special import order - there aren’t going to be many waiting to be scrapped... lol.
I feel like I'm becoming an expert at The Art of the Immaculate Compromise...

rx7locost
This is just brilliant - always love a photo or a diagram. What you have done here is almost exactly what I was imagining... except... where I was thinking of removing all trace of the strut, and then trying to mount a ball-joint directly to the upright... your method of using the MacP bracket is so much better... and a wizard wheeze... And, if you fit the bolt inside the adapter-bracket it will be pretty(er) as well - although it’s amazing what a dab of paint, and big fenders will do... lol.

Having spent two days online looking for ‘solutions’ I've now spent an hour staring at the sheer simplicity of your solution. I feel so relieved this night... Thank you.


For All...
One thing I'm thinking... what to do about the loss of the driveshaft - I'm assuming the rear face of the upright needs to be covered, to protect the hub/bearing. Do I just screw or weld a steel plate over the hole...

Many thanks all, Mangpong.
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PostPosted: April 16, 2018, 3:06 pm 
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Joined: April 26, 2008, 6:06 pm
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Location: Under the weather. (Seattle)
Rather than cutting and drilling on the stock spindle, I prefer bolt-on adapters that have no chance of compromising the integrity of the factory parts...More like these.

Image

...Or these.
ImageImage

...Or these
ImageImage

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PostPosted: April 16, 2018, 7:34 pm 
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Joined: January 2, 2009, 1:45 pm
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Location: Halifax, Nova Scotia
Or, look for the knuckles off the front of a 2-wheel drive (rear wheel drive) pickup truck. My suspension donor is a 1989 Isuzu Pickup. A Toyota may be more common for you. Toyota 2 wheel drive vans used to be popular too.

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PostPosted: April 16, 2018, 9:00 pm 
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Joined: December 17, 2010, 1:24 pm
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Location: Gainesville, Mo.
Toyota Previa comes to mind!

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