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T89 Designs Razorbill - Design and Build
Doctor Derek Doctors - 5/12/18 at 05:56 PM

So 4 years on from the start of T89 SSL build diary with the car designed, built, raced, developed, magazine featured and finally sold its time to start all over again.

Over the past 4 years the 3 most asked questions have been:

1) Can you do one with a full body so I can use it on trackdays
2) Can you do one with a car engine
3) Can you do a Chain drive Diff Version

I addressed 1 & 3 with the Sports Racer and Chain drive Diff add-on packs for the Single Seater plans but I wanted to properly cover 2) and do a single donor, car engine Sports Racer / Sports Libre car that could be used for trackdays, sprints, hillclimbs and racing.

I have decided to use the same Lola T492 recreation body from Equinox products as its gorgeous looking, simple and relatively cheap (~2000 for a complete set)

For the engine it was a pretty simple choice, I have decided to use the B5/B6 era VW/Audi Passat/A4 1.8T Engine and gearbox, its a bit of a no-brainer for the following reasons

- They are dirt cheap, B5 Passats and A4s cost around 300 to 500
- The engine is robust and hugely tuneable, 150 upto 500bhp with 250bhp achievable for very little cost
- They use a longitudinal transaxle mimicking the layout style of a Hewland without the huge bill
- The uprights use a bolt in hub carrier (like the rear of a sierra) that can be easily bolted to a bespoke upright
- The gearbox is the same as a Porsche Boxster meaning a Mid-engine gear linkage is available from ebay & breakers
- There is a big aftermarket community around these engines meaning readily available mod parts like uprated clutches.

Other choices made so far are:

- Locost/Haynes inner wishbone bushes
- A universal upright that is used on all 4 corners
- Wilwood Powerlights all round
- Mk2 Escort Steering rack (the Lola originally used this as well!)
- Full MSA spec ROPs
- Minimal parts fabrication, I want more off-the-shelf parts that the Single Seater

I am currently deep into chassis design and will post pictures up ASAP, there are plenty on and T89 Designs Instagram and Facebook already.

jeffw - 5/12/18 at 07:21 PM

Going to be epic Cal, looking forward to a drive

MikeR - 6/12/18 at 12:27 PM

First thought - if people are competing they're likely to want to be competitive. Bearing in mind MNR and MB both have fully bodies which have been through wind tunnels it may be worth designing the chassis so it possible to adapt / change the body easily. That way if the car is great but the aero lets it down then it wouldn't be a major issue to update the aero.

Ok actually my first though was "cool". Good luck and keep people posted. I've often wondered about doing something similar with the mechanicals on a road legal single seat 1960's designed car. Having not finished the locost its still a dream.

Doctor Derek Doctors - 6/12/18 at 02:28 PM

The question of competitiveness can be addressed in two ways, 1) What is its actual competition and 2) Will it actually be uncompetitive.

Starting with 1) first. Neither the MNR F17 or the AB Escala/Sabre are actually in competition with this car. For a start this is a homebuild designed with price and manufacturability in mind so people wont be aiming for the same end result as if buying one of those. Also the MNR F17 (I think) is bike engine only so its a completely different thing. And while there is a car engine AB Escala, a full Ecoboost build will be ~10x the price of this car to build thus considering them in direct competition is a waste of time, if you can afford 10x the price you'll be buying something 10x more expensive. I've been mindful not to design something that's already out there available (IE an ultra developed Bike Engine Sports Racer) and isn't aimed at the same class (I don't think there is any race series apart from the pretty high level OSS Championship where this could race against either the AB or MNR.

And with point 2) they have been in a windtunnel which from talking to Andy and Marc has been aimed at reducing drag due to the bike engined roots of the cars. But with this, while the upper body may be from 1978 the underside is much more developed, the Lola body with its high sides leaves room for two huge underbody venturis running down either side that, combined with a specially designed pair of wings should generate massive downforce. Fitted with an engine that can easily go to 300bhp makes it more of a High Power/High Downforce CEC than a Low Weight/Low Drag BEC

People levelled a similar criticism to the SSL project "it wont be able to compete with a Gould/OMS/Force" which was a strange comparison to make as its a 5k homebuild car and also didn't turn out to be entirely true, with my little homemade 600cc car holding its own on the timesheets.

We'll see how it goes though... and hopefully the picture uploading might get fixed so I can add pictures!

Other random details:

- I have now weighed the engine and gearbox and it comes in at a not very svelte 193Kg but this is everything including the diff and fluids
- A very kind gentlemen is sending me a spare GTS turbo kit that should push me to over 275bhp
- I am going to use some aluminium monocoque style parts on the chassis, I'm hoping this will keep weight down and make the chassis build a lot simpler.
- I have now confirmed that 280mm Audi brake discs and Powerlite caliper will fit inside a 13" wheel, sadly there are no 15" tyres small enough to fit under the body which was designed for small 13" 70's cross-plys
- The full Boxster gear linkage has now been sourced for 80 from ebay, it will have a Porsche gear lever!
-The universal upright is nearly finished in terms of design and I am hoping to order one to test assemble imminently.

AdamR20 - 6/12/18 at 02:32 PM

I like your mantra with this - I'm also a huge believer that a 'shed build' can trump something 'professional'.

Very keen to follow progress and see how it turns out, thanks in advance for sharing!

[Edited on 6/12/18 by AdamR20]

jeffw - 6/12/18 at 09:44 PM

MikeR - 7/12/18 at 09:13 AM

Not sure about the wooden bits but that looks fab.

jeffw - 7/12/18 at 01:05 PM

Some low cost Marine Ply would be the answer

jeffw - 7/12/18 at 01:07 PM

This is what it will/could look like

Doctor Derek Doctors - 7/12/18 at 05:36 PM

Originally posted by MikeR
Not sure about the wooden bits but that looks fab.

The area where the wood is (extending in to the side of the chassis), is where the full length venture tunnels will be. With an area of 340 x 250mm down the side opening up at the rear they should be pretty powerful.

I'm tempted to veneer panel them to go for a 'Woody' effect.

In other news;

-Boxster gearbox mounts have gone on to replace the original Audi mounts, these are lighter tidier steel mounts than the large aluminium castings on the Audi and mate up to the chassis much lighter.
- The Turbo kit is on its weigh from America
- The body has been weighed and the whole lot comes in at 40.5Kg
- Current weight calculations put it at 530-550kg ready to race.
- Initial investigation into the cooling system shows that it will nicely connect up to a rear mounted Polo radiator

ettore bugatti - 8/12/18 at 06:43 PM

Great project!

Interesting to see how the chassis and suspension develops out.

How flexible is the chassis for different drive trains?

I can imagine, people want to stick boxer engines or v8s in that space.

Doctor Derek Doctors - 8/12/18 at 08:52 PM

The Audi and Porsche Boxster 5-speeds. Are all the same gearbox so that gives a pretty wide choice of I4s, V6, V8 and Flat 6 engines. I'm pretty sure an Impreza flat 4 could be converted to FWD layout to sit in the back of this as well.

The chassis is 950mm wide a cross the roll hoop so plenty of width and due to the Lola originally having a Hewland with a large bellhousing the rear bulkhead and roll hoop are surprisingly far away from the rear axle centre line so there is plenty of length as well.

Latest update, I have just bought a cheap pattern clutch slave cylinder, these come with a normal screw in brake pipe fitting rather than the plastic push fit rubbish that Audi and Porsche fit as standard.

Ugg10 - 8/12/18 at 09:11 PM

Looking very good, love the concept, how woukd thus compare to a Spire GTR? There are some of these with the Audi 1.8t in the back, looks like a similar concept.

The scoops can be made FWD only by removing the centre diff and putting in a locking spigot and a new rear plate. I think it only works with 5 speed boxes, this is what was used in the SDR Storm WR3 iirc, the current storm owner may be able to provide the conversion and gear change and kits are also available from AUS.

A 2.7 twin turbo fromthe A6 crossover thingy would be rapid but heavy.

Any way of making it road legal?

Doctor Derek Doctors - 16/1/19 at 05:49 PM

Right I have the pictures working on my website now.

Picture of Brake Clearance, 280mm is the smallest front brake discs Audi did on a 5 stud PCD, they do a vented and solid in this size. For racing I will fit vented at the front and solid at the rear, the upright is designed such that the caliper can be mounted 10mm further in with the discs machined down to 260mm to aid clearance on cast wheels. Clearance on the 280mm discs and Wilwood caliper in a split rim is a whopping 3mm

[Edited on 18/1/19 by Doctor Derek Doctors]

Doctor Derek Doctors - 18/1/19 at 05:50 PM

Some CAD renderings of what the car should look like:

Doctor Derek Doctors - 18/1/19 at 05:51 PM

Powertain just out of the car, Engine, gearbox, driveshafts and hubs will all go into the car fairly un-modified. This is a 150bhp model but light tuning should take it to 200+bhp

[Edited on 18/1/19 by Doctor Derek Doctors]

Doctor Derek Doctors - 29/1/19 at 05:43 PM

The chassis came together at Bespoke Auto Designs last:

Laser Cut Suspension Towers:

MSA Compliant Roll Hoop

Floor and Upper Suspension Frame, made flat so easy to cut, jig and weld:

How the suspension towers fit on:

The suspension towers and the two roll hoops support the upper suspension frame, giving you and outline chassis frame with ease.

Triangulation Added, just 17 hours to get to this point, only final weld to do:

jeffw - 29/1/19 at 07:06 PM

Really coming along Cal, looking forward to a drive in it

CNHSS1 - 29/1/19 at 07:58 PM

Really loving the work

Tempted to have a gander at it once finished at an event

[Edited on 29/1/19 by CNHSS1]

Mr Whippy - 30/1/19 at 12:45 PM

that's a great solution for a building table

HowardB - 30/1/19 at 04:44 PM

Originally posted by Doctor Derek Doctors
The chassis came together at Bespoke Auto Designs last:

Laser Cut Suspension Towers:

MSA Compliant Roll Hoop

Floor and Upper Suspension Frame, made flat so easy to cut, jig and weld:

How the suspension towers fit on:

The suspension towers and the two roll hoops support the upper suspension frame, giving you and outline chassis frame with ease.

Triangulation Added, just 17 hours to get to this point, only final weld to do:

mmmmm tab and slot - all sheet metal should be tab and slot!

did you ever see the boat hull design by British Steel that was tab and slot?

Doctor Derek Doctors - 6/2/19 at 05:44 PM

Chassis back fully welded from Bespoke Auto designs, its smaller than I though but is superb quality. I will be making some design changes to make it easier to weld but over dimensions will be unchanged.

Front body section almost drops straight on, just needs some trimming, a lot less hassle than I thought it would be:

The engine fits as well but is very tight, big power turbo's may need a bit of a 'speed notch' in the chassis:

Plenty of room for the fuel tank(s) and in front of the engine:

Mike Wood - 29/6/19 at 05:34 AM


Looks great! Any updates please?

What's the story in making or sourcing the bodywork in terms of what is in the production plan set for self-builders?


Doctor Derek Doctors - 29/6/19 at 01:52 PM

I'll try and do some updates on here but with the photo uploader not working it's a big pain in the bum. I do regular updates on Instagram and Facebook as its so easy from my phone. Follow T89 designs on FB and T89 RaceCarWings on Instagram.

The body is off shelf from Equinox, ready to go for the build. No manufacturing required.

40inches - 29/6/19 at 02:43 PM

The photo uploader was fixed a few weeks ago