Designing a locost style Lotus 7 Replica

[Caffeine]

I want to build a lotus 7 replica (or 'Clubman')

I've been looking at various options regarding purchasing a kit, of which the main players in Australia seem to be Westfield, PRB/Birkin and Fraser.

Caterham also offer a model in Australia, but the cost is somewhat prohibitive (~$100k)

The above manufacturers offer various levels of 'kits', which can be purchased and used as a base for building your own car. However, these kits are very comprehensive and it seems that you are assembling a car, rather than building one.

Additionally, I'm rather large, being 2m tall and weighing over 100kg, there's not much hope of fitting me into a standard sized kit car.

The other popular option is to build a car from scratch, and most people follow the designs and guidelines in Ron Champion's book 'Build Your Own Sports Car for as Little as £250', which is known in kit car speak as 'the book'.

Cars built using 'the book' are referred to as 'Locost' cars. They can be made very cheaply (probably not the AUD equivalent of £250, but cheaper than buying a kit) and they can obviously be modified to suit the driver.


A large enthusiast community has developed around 'the book' and various players offer parts to suit 'book' chassied cars and people also make available customised designs based on 'the book'. A notable example of this is www.mcsorley.net, which offers plans for a '442' chassis, being 4 inches wider, 4 inches longer and 2 inches taller than 'the book' chassis.

So, I started laying out a locost style car based on 'the book', but which will have various enhancements and dimensional changes to allow me to actually drive it.

I'm using solidworks, because I'm familiar with it and it allows me to change the design and regenerate plans for the car easily.

My initial model is purely a copy of 'the book' chassis, which, once complete, I will then modify to suit me.

[Caffeine]

Here is the book chassis, with a solidworks copy of me in it (thanks to www.dpcars.net for the human body model, which I have then scaled to my approximate dimensions...



And here is a rendering of my model of the standard book chassis (using all 1in by 1in 1.6mm square tube for simplicity)



There is lots of information at the Clubman Builder's Resource (http://locost7.info) including a couple of documents detailing ways of increasing the stiffness of the book chassis by ~350%, while increasing weight only 15 or so kilograms! I'll definitely be incorporating those changes into my model.

[Caffeine]

And here is a side by side comparison of my model and a basic book chassis available from www.mcsorley.net

Side by side

Since I took this screenshot I've fixed up a few problems with mine in the rear section, which was causing it to be shorter than it should be.

Solidworks takes my model, and converts it to a 'cut list', which shows me how long each piece should be, and what the end profile should be. I can regenerate this at any stage and cut the physical tubes to suit, it should then be perfectly accurate

Additionally, I'll be able to create 1:1 scale drawing documents, which I can get a plan printer to print out life size, allowing me to work directly off a life sized plan

[Mactype]

I'm one of the guys who started ozclubbies.com so have been around them for quite a bit.

Couple of points:

Be a little careful with regard to what your looking at/planning to build. Just because it looks like a clubman doesn't mean their all of the same ilk.

Rego is the biggest dilemma and if you look through the threads on Ozclubbies theres numerous hard luck stories of people who started a build with a engine that will satisfy the relevant rego authorities only to find as their nearing the end, rules have changed and its now not suitable.

Costs of lo-costs - most end up costing their owners anywhere from $15-25k in total, for that money you can buy a far better chassis in an older PRB or Westfield thats already registered saving you lots of hassle, their easy to work on and you can then amuse yourself pulling it apart and rebuilding. With regard to your size I'd be going and plonking your arse in a few, the Westfields are pretty big as is (the locost book is based on an old Westfield BTW) the +4 varieties are massive and really take away from what a clubman is supposed to be IMHO (and must weight heaps).

Still heaps of fun when finished

[Caffeine]

Costs of lo-costs - most end up costing their owners anywhere from $15-25k in total, for that money you can buy a far better chassis in an older PRB or Westfield thats already registered saving you lots of hassle, their easy to work on and you can then amuse yourself pulling it apart and rebuilding. With regard to your size I'd be going and plonking your arse in a few, the Westfields are pretty big as is (the locost book is based on an old Westfield BTW) the +4 varieties are massive and really take away from what a clubman is supposed to be IMHO (and must weight heaps).

Still heaps of fun when finished

Thanks for the input, but I'm more interested in building one from scratch than buying a prebuilt chassis.

As for engine options, I'm leaving that open at the moment, I'm not going to start building this thing for a long time yet, and when I do I'll be looking very carefully at what engines are suitable (the NC looks like a nice donor vehicle at this stage )

I've sat in a few different types, and none of them (including the westfield widebody) fit me very well.

From looking at the mass properties tools in solidworks (which are suprisingly accurate) a width increase definitely adds some weight but it isn't ridiculous.

[Mactype]

As long as your aware the options - go for it.

You'll find the actual chassis the lightest bit, its once you start hanging everything off it that weight starts to build - which doesn't matter if your after a cruisy car really (I've seen them weighting up to 950kg). You've probably already sussed out the required torsional stiffness required in NSW for a lo-cost chassis that the book doesn't address.

PRBs and Caterhams will be anywhere from 500-600kgs (my prb was fairly well stripped with lightweight everything and was 535kg), Westfields more like 650-700kg's and most locosts I've seen teeter around the 700-750kg mark.

FMS01 (Julian) on here built one and used to sell a set of chassis plans for a clubbie along with brackets etc...

[orx626]

Here's a Locost being built using NC running gear (by a gentleman in Melbourne IIRC).



http://www.locost.ozcarnut.com/html/photo_album.html

Cheers,
Danny

[Okibi]

Have you checked out

http://www.flyinmiata.com/westfield/

http://www.flyinmiata.com/index.php?deptid=4515&parentid=0&stocknumber=46-86005

[SuperMazdaKart]

if i were to try building a car it'd look like something more suitable to Scrapheap Challenge

[Caffeine]

Here's a Locost being built using NC running gear (by a gentleman in Melbourne IIRC).



http://www.locost.ozcarnut.com/html/photo_album.html

Cheers,
Danny

I've seen that one, looks very nice although he's using the auto

[orx626]

I've seen that one, looks very nice although he's using the auto

I understand that he is a paraplegic, hence an auto is a better solution.

Cheers,
Danny

[Caffeine]

Have you checked out

http://www.flyinmiata.com/westfield/

http://www.flyinmiata.com/index.php?deptid=4515&parentid=0&stocknumber=46-86005

Yep, but Keith stats with a prebuilt chassis too, takes all the fun out of it

A prebuilt chassis would be awesome though, but none of them seem to fit me

[Caffeine]

I've seen that one, looks very nice although he's using the auto

I understand that he is a paraplegic, hence an auto is a better solution.

Cheers,
Danny

Wow that makes sense then.

He's doing an amazing job to build a car then!

[Mactype]

I understand that he is a paraplegic, hence an auto is a better solution.

Cheers,
Danny

Thats truly awesome

[bigdog]

Time for a trip to chez Bigdog Caff - you can have a good look over my clubman and a test sit - but if I fit then you will too Lots to be learned from looking at someone else's interpretation of the genre. Let me know when you want a looksee... I have a copy of the original book too if you haven't read it.