# Build a mini caterham



## mr-mechanical (May 18, 2020)

So last year I bought drawings from @gbritnell for his straight 4 cylinder engine. 

I intend to build the engine in the future but have decided that I'd like to have it drive a car.

In the past I have considered building a caterham / lotus 7 replica but never got round to doing due to fund or available space. But I did buy a book for building the chassis / car.

So I have decided to build the car at a scale that will work with the 4 cylinder engine.

In this project I will need to design and build a gearbox and dif etc. to make the car drive. A major project!

I have made a start and the car a few month ago and so far I have made the chassis, wishbones and front and rear uprights. 

Here's are photos of progress to date:


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## goldstar31 (May 18, 2020)

My son has just finished a rebuild of a 12" to the foot Lotus Elise SE having the wishbones etc powder coated.
To get room in his garage, I got his/ once mine Merc SLK230 back and had to leave my little Skoda outside.

He now wants a left hand drive Citroen Deux Chevaux to rebuild. 
It never stops

Cheers
Norman


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## mr-mechanical (May 18, 2020)

goldstar31 said:


> My son has just finished a rebuild of a 12" to the foot Lotus Elise SE having the wishbones etc powder coated.
> To get room in his garage, I got his/ once mine Merc SLK230 back and had to leave my little Skoda outside.
> 
> He now wants a left hand drive Citroen Deux Chevaux to rebuild.
> ...


Great, I wish I still had space for a full size car project. My last car project was the rebuild of a Mazda RX8 Wankel engine.


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## BaronJ (May 18, 2020)

Hi Guys,

A few years or so ago, I was maybe fifteen or sixteen at the time. I helped a friend build a Lotus 7.  It had an Austin 1.5 Ltr engine in it. Bog standard no frills.  It used Triumph Herold front suspension and a Ford Popular rear axle.  Unfortunately I never drove it, however the first time I rode in it, with my friend George driving it frightened me terribly and I refused to go back in it.


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## gbritnell (May 19, 2020)

To simplify the drive parts why not look into using a centrifugal clutch from something lik a chain saw or weed eater?
Making a mechanical clutch and gear box would certainly be very cool but would certainly be more complicated
gbritnell


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## mr-mechanical (May 19, 2020)

gbritnell said:


> To simplify the drive parts why not look into using a centrifugal clutch from something lik a chain saw or weed eater?
> Making a mechanical clutch and gear box would certainly be very cool but would certainly be more complicated
> gbritnell


Thanks George good idea.
I did have a question regarding the flywheel. Is there anything critical to the details of the flywheel? I.e. mass?
Or can I make any flywheel of my design to working with the crankshaft?


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## Peter Twissell (May 19, 2020)

I see you're basing your model on the CSR (independent rear suspension).
I designed that suspension!


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## teeleevs (May 19, 2020)

mr-mechanical said:


> So last year I bought drawings from @gbritnell for his straight 4 cylinder engine.
> 
> I intend to build the engine in the future but have decided that I'd like to have it drive a car.
> 
> ...


Great going, keep up the good work. Ted from down under.


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## mr-mechanical (May 19, 2020)

Peter Twissell said:


> I see you're basing your model on the CSR (independent rear suspension).
> I designed that suspension!


Very interesting! Do you work for caterham?


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## wthomas (May 19, 2020)

Sir:
     For your information Crosley built their Diff. (Rear end) with
bevel gears that can easily be machined without special machines.


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## goldstar31 (May 19, 2020)

It may not be relevant  but I cut the 4 lawns today with a Briggs and Stratton powered sit on lawn mower.
3 forward  and one reverse speeds and a crash gear box-.I passed my car driving tests on a 1st gear crash gear box.

And then   being in lockdown and 90/and disabled, I had a run around on my £200( 2nd hand) disabled scooter. A bit faster that my fit son can walk!  In pre-virus days, my 4 grand kids all enjoyed 'my toys'

Cheers

Norman


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## craigdiver (May 20, 2020)

mr-mechanical said:


> So last year I bought drawings from @gbritnell for his straight 4 cylinder engine.
> 
> I intend to build the engine in the future but have decided that I'd like to have it drive a car.
> 
> ...


Absolutely love it, of course I'm biased as have built a full size one.


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## mr-mechanical (May 20, 2020)

craigdiver said:


> Absolutely love it, of course I'm biased as have built a full size one.View attachment 116462


Very nice! What's the ground clearance to the under side of the chassis on a full size one?


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## craigdiver (May 20, 2020)

I have went for BMW power so engine is quite tall. This is giving me 75mm (3") ground clearance.


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## craigdiver (May 20, 2020)

mr-mechanical said:


> Very nice! What's the ground clearance to the under side of the chassis on a full size one?



75mm (3")


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## gbritnell (May 20, 2020)

There is nothing critical about the flywheel dimensions. The diameter is the most important. The smaller you make it the higher the idle RPM goes up. You need the flywheel's mass on the O.D. 
gbritnell


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## Peter Twissell (May 20, 2020)

I didn't work directly for Caterham. I work for Multimatic and we were contracted to design and develop the CSR suspension.
Re. flywheels - a light flywheel can make the car very difficult to drive. I drove one of the prototypes from Norfolk back to Dartford. It had a light flywheel, about an inch of throttle pedal movement and a clutch which had a similar effect to just jamming it into gear. Manouvering around the car park at work was just a series of launches and equally abrupt stops.


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## mr-mechanical (May 21, 2020)

Peter Twissell said:


> I didn't work directly for Caterham. I work for Multimatic and we were contracted to design and develop the CSR suspension.
> Re. flywheels - a light flywheel can make the car very difficult to drive. I drove one of the prototypes from Norfolk back to Dartford. It had a light flywheel, about an inch of throttle pedal movement and a clutch which had a similar effect to just jamming it into gear. Manouvering around the car park at work was just a series of launches and equally abrupt stops.


Cool. I don't suppose you would have any contacts that could help me get hold of a cad model on the body work that I could scale to my chassis would you? I'm planning on 3d printing molds and making carbon fiber panels


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## Peter Twissell (May 21, 2020)

Tricky. I might have the CAD somewhere, but I'm not in a position to distribute it.
That said, Caterham bodywork is pretty simple. The only parts you need are the nose cone and mudguards - the rest is just skins on the chassis.


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## Peter Twissell (May 21, 2020)

This any good?


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## Peter Twissell (May 21, 2020)

I worked with Jez Coates and Paul Crankshaw at Caterham - both have since left the company.
I've sent an enquiry to Owian Davies, who is a senior engineer and still at Caterham.


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## mr-mechanical (May 21, 2020)

Peter Twissell said:


> This any good?


Thanks, yes that's great!


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## Jules (May 22, 2020)

mr-mechanical said:


> Thanks, yes that's great!


Good luck with the Caterham. 
A mate of mine had just finished one. About 220 BHP Ford Durertec. 
Crazy expensive!!!!
About £40k
and you have to build most of it yourself.


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## Peter Twissell (May 23, 2020)

And where else would you get 400+ hp per ton for £40k?
Oh yes - motorcycles.


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## Jan Dressler (May 24, 2020)

mr-mechanical said:


> Cool. I don't suppose you would have any contacts that could help me get hold of a cad model on the body work that I could scale to my chassis would you? I'm planning on 3d printing molds and making carbon fiber panels


When looking for more "technical" CAD models, check out Grabcad. I remember that I did find some Caterham / Lotus / Locust / Super 7 related stuff there, but that was years ago.  
Just give the authors the credit they deserve 

Regards, Jan


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## mr-mechanical (Jul 2, 2020)

So over the last couple of weeks I've made the steering rack for my mini caterham project and got it fitted. Good to see some moving parts

I've also have a nose cone 3D printing so I can work out what space I have for the radiator which I've bought. (PC radiator)

I've also bought a module 1 - 75mm dia gear which I intend to modify for my flywheel. This way I can use a starter motor.


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## Peter Twissell (Jul 3, 2020)

If you wanted to add some rubber gaiters to the steering rack, can I suggest the gaiters found on bicycle or motorcycle cables?


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## mr-mechanical (Jul 3, 2020)

Peter Twissell said:


> If you wanted to add some rubber gaiters to the steering rack, can I suggest the gaiters found on bicycle or motorcycle cables?View attachment 117551


Great idea, I'll have a look at what sizes are available and if it work with what I have.


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## Peter Twissell (Jul 3, 2020)

Is that last image a centrifugal clutch? Do you intend to run a gearbox with shift function?


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## mr-mechanical (Jul 3, 2020)

Peter Twissell said:


> Is that last image a centrifugal clutch? Do you intend to run a gearbox with shift function?


Yea that's a centrifugal clutch. I plan to make a single speed gearbox initially but in the future I may look to add more speeds.


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## Peter Twissell (Jul 3, 2020)

If you want to make a multi speed box to work with the centrifugal clutch, I would suggest a planetary / brake band type - see Ford Model T gearbox for more detail.
The supercharger drive on my radial uses a planetary / brake band arrangement to switch between low and high speeds.


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## mr-mechanical (Jul 3, 2020)

Peter Twissell said:


> If you want to make a multi speed box to work with the centrifugal clutch, I would suggest a planetary / brake band type - see Ford Model T gearbox for more detail.
> The supercharger drive on my radial uses a planetary / brake band arrangement to switch between low and high speeds.


Thanks I'll have a look


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## jeff.gearing (Jul 4, 2020)

I used to run Traxxas UK (RC company for electric and IC models) I have some parts left over from those days, including some gaters, let me have your address and I will send some up to you. We also did an IC model with an auto 2 speed box and reverse (T-Maxx) will try and find some details that might help.


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## mr-mechanical (Jul 4, 2020)

jeff.gearing said:


> I used to run Traxxas UK (RC company for electric and IC models) I have some parts left over from those days, including some gaters, let me have your address and I will send some up to you. We also did an IC model with an auto 2 speed box and reverse (T-Maxx) will try and find some details that might help.


Thanks Jeff, I've sent you a message


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## mr-mechanical (Oct 11, 2020)

Its been a while since my last update - got a bit distracted during lockdown with other projects - including the rewiring of a denford CNC micro mill.

This weekend I made some more progress on the Mini Caterham project and made the rear wheel hub bearing carriers. The parts were made using the said CNC milling machine


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## JCSteam (Oct 16, 2020)

jeff.gearing said:


> I used to run Traxxas UK (RC company for electric and IC models) I have some parts left over from those days, including some gaters, let me have your address and I will send some up to you. We also did an IC model with an auto 2 speed box and reverse (T-Maxx) will try and find some details that might help.


Off topic but one of the most fun R/C cars I owned was a Traxxas Stampede, Went anywhere and I don't think I ever broke anything on it, even taking it over tree roots and down a 30' slide. Great memories!
Jon


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## goldstar31 (Oct 16, 2020)

JCSteam said:


> Off topic but one of the most fun R/C cars I owned was a Traxxas Stampede, Went anywhere and I don't think I ever broke anything on it, even taking it over tree roots and down a 30' slide. Great memories!
> Jon



I sort of recall the feeling because I had a house in the Balearic Islands in Spain and there was a wreck of a Seat 600 but this was one of 32. It was a Noddy one with noroof, factory built and with wicker work seats.
I was doing a City and Guilds in Motor Vehicle Restoration and my plan was to buy it-- and a donor car and bring them home in a furniture van.
The owner of the 600 was a miserable git and his price was astronomical.
Evenually,the car was literally broken into and finished up as infill at the local football ground in Cala N'Porter.
However being me, all was not lost and I'd bought a  SEAT 126- old, smelt of fish and almost past it and I taught my two kids when each was 14 to drive on the local beach after the visitors had left for the day.
So Discussion with son about Christmas boxes and I've found that locally kids of 12 can hire a car at the local newcastle race course----- using GrandPa's money- of course.

As one says-- More Anon

Norman.

Sometime in the distant oast, I wanted a Mini Marcos kit car. I was already with a home made Mini Cooper engine---- and was too tall to fit in-- like son's Lotus.  The only thing that fits in is my wallet/pocket book!!!!

I'm still 'baby sitting' an immaculate Merc SLK230 Sports


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