55 replies to this topic

[jeremy durward]

I’m wondering if anyone knows exactly what changed between the Lotus 25 and the 33? I’ve found lots of fairly vague references to redesigned suspension and slightly altered chassis but definite information seems hard to come by. So far the obvious differences of 13” wheels and flat plane crank engine aside it seems that the upper rear radius rod was raised on the inboard and outboard ends and the chassis inner was straightened out (although I can’t find a good picture of this). Were there any other changes?

[mariner]

Mostly but in the details, I am sure more expert members will add to these

 

1) The wheels were obviously 13" not 15"

 

2) the inner chassis sides were one straight taper from just in front of engine to the front bulkhead. This was easier to build and added fuel space versus the kinked ones on a 25.

 

3) The radiator exit area was re-designed to provide a vee shaped oil tank  to aid air out of rad.

 

4) The front rad area was changed to allow the Lucas fuel pump " bomb" to get cold air up front.

 

5) At some point the gearbox went from ZF to Hewland.

 

6) as you say the radius arm chassis mounts were revised. The 25 started with rubber bushes (!) but went over to ball joints and stronger chassis brackets. The bottom lower front wishbone rear mount on the original 25 was a sort of depression in the sheet alloy skin with a bracket clamped on . This had to be replaced by a more solid bracket.

 

I think part of the problem is that the 25's were continuously updated as were the 33's as they were rebuilt  after accidents etc so lots of differences within 25's and 3's as well 

Edited by mariner, 15 June 2019 - 14:59.

[Tim Murray]

2) the inner chassis sides were one straight taper from just in front of engine to the front bulkhead. This was easier to build and added fuel space versus the kinked ones on a 25.

This used to be the accepted thinking until the confusion over which 25 chassis was which was resolved in around 2013. It’s now clear that the first two 33 chassis, R8 and R9, were built with the kinked inner monocoque like the 25. Here’s the current thinking, from the ORC site:

After two seasons of using the Lotus 25s, Team Lotus introduced a revised model, the Lotus 33, during the 1964 season. The car was designed around Dunlop's new 13-inch tyres, and was generally slimmer, lighter and stronger than its predecessor. Two cars, R8 and R9, were built to this pattern. For 1965, Lotus introduced a further revision to the 33, using using single-plane straight inner skins, a much simpler method of construction, and built R10 and R11 for works use that season. Jim Clark won Grands Prix during 1965 in chassis R9, R10 and R11. A further car, R13, was supplied to Reg Parnell Racing later in 1965, replacing an older Lotus 25 that had been wrecked at the Belgian GP. In 1966, chassis R14 was built to use a 2-litre BRM V8 engine, as the development of the BRM H16-powered Lotus 43 had not progressed as well as expected. The missing number in the sequence, R12, was the Lotus 39 Tasman car.

[Roger Clark]

The quote from ORC in Tim Murray’s post should say that R14 was built for the 2-litre Climax engine, not BRM - ORC’s mistake, not Tim’s.

As has been said, the 25s were modified during 1964 to bring them closer to 33 specification. The most obvious changes were to the suspension, to make better use of the new, wider 13inch Dunlop tyres. The changes were not consistent as Jim Clark sometimes preferred to the 15inch wheels. He drove R6 at Monaco and Zandvoort with 13 inch wheels ant the upper rear radius rod attached at the top of the hub carrier. This was referred to by some journalists (but not, I think, by Team Lotus) as the 25D specification. At Spa he drove the same car with 15 inch wheels and the radius rod at hub level.

One difference between the 25 and the 33 which hasn’t been mentioned yet was the the 33 had a ¾ inch longer wheel base. This was reported by Denis Jenkinson the the Monaco Grand Prix, so must have applied from R8. It’s not an easy difference to detect from photographs though!

[jeremy durward]

Mostly but in the details, I am sure more expert members will add to these

 

1) The wheels were obviously 13" not 15"

 

2) the inner chassis sides were one straight taper from just in front of engine to the front bulkhead. This was easier to build and added fuel space versus the kinked ones on a 25.

 

3) The radiator exit area was re-designed to provide a vee shaped oil tank  to aid air out of rad.

 

4) The front rad area was changed to allow the Lucas fuel pump " bomb" to get cold air up front.

 

5) At some point the gearbox went from ZF to Hewland.

 

6) as you say the radius arm chassis mounts were revised. The 25 started with rubber bushes (!) but went over to ball joints and stronger chassis brackets. The bottom lower front wishbone rear mount on the original 25 was a sort of depression in the sheet alloy skin with a bracket clamped on . This had to be replaced by a more solid bracket.

 

I think part of the problem is that the 25's were continuously updated as were the 33's as they were rebuilt  after accidents etc so lots of differences within 25's and 3's as well 

 

Thanks Mariner. You are correct in that a lot of the confusion comes from the constant change of spec in the cars. I sometimes think it's better to look at the 25 and 33 as the same car that was developed so much they thought it best to give it a new designation. perhaps the better question from me would be what were the differences between the car that won Jim Clark's first championship and the car that won his second? And by that i mean the specific car in the race that he clinched the championship.

 

Do you know of any photos that show the changes to the radiator area and the change in the chassis? I have found photos that show the difference in the cockpit opening area of the chassis, but not further down. do you know when the change to Hewland happened? I have noticed the Hewland in the back of Hill's car at the Monaco 67 race, but I've always wondered if that was just because he was running the BRM motor in that race?

[Roger Clark]

I don’t believe that Team Lotus ever made a full change to Hewland gearboxes.

They experimented with Colotti and Hewland in 1963: Taylor drove R2 at Zandvoort, Reims, Silverstone and Nürburgring with a Colotti, R6 had a Hewland when it first appeared in the non-championship Austrian Grand Prix - this was, I think, the only time Jim Clark raced a 25/33 with other than a ZF.

In 1964, modified ZF boxes were obtained and became standard for that year and 1965.

In 1966, R11 had a BRM gearbox when Arundell drove it in the British Grand Prix with a BRM engine. Jim Clark had previously raced it with Climax and ZF. In 1967 it had a Hewland when Graham Hill drove it in the International Trophy and Monaco Grand Prix. This was the last time that Team Lotus raced a 33 so I suppose you could say that they marked a change to Hewland.

The Parnell team cars used Hewland throughout 1964 and 1965. Paul Hawkins had a ZF in his 33.

Edited by Roger Clark, 16 June 2019 - 20:45.

[jeremy durward]

I thought that was the case Roger, more testing and playing with things than making a change to a different gearbox supplier.

[Ray Bell]

I'd expect someone around here has pics of the 39 with the nose off to help see the front of the chassis...

Wirra? Dick Simpson?

[Roger Clark]

I believe that the v-shaped oil tank and slimmer radiator first appeared in 1963 and so were nothing to do with difference between the 25 and the 33. There is a photograph in Ian Bamsey’s book Lotus 25 - A Technical Appraisal showing the oil tank.

Bamsey also says that the installation of the fuel injected Climax engine required a 1 inch increase in wheelbase. Fuel injection first appeared on R4 in South Africa, December 1962. R5 was brand new in South Africa but had a carburettor engine at that stage. I don’t know whether the 1962 cars were modified with longer wheelbase. The first new car for 1963 was R6 which appeared in Austria in September.

I don’t understand mariner’s point (4) about the front rad area being changed to allow cold air to get to the Lucas “bomb”, the high pressure pump for the fuel injection. I thought that Lotus fitted the bomb at the back of the car, next to the gearbox. They may have moved it later but I couldn’t find any record of that.

[jeremy durward]

I believe that the v-shaped oil tank and slimmer radiator first appeared in 1963 and so were nothing to do with difference between the 25 and the 33. There is a photograph in Ian Bamsey’s book Lotus 25 - A Technical Appraisal showing the oil tank.

Bamsey also says that the installation of the fuel injected Climax engine required a 1 inch increase in wheelbase. Fuel injection first appeared on R4 in South Africa, December 1962. R5 was brand new in South Africa but had a carburettor engine at that stage. I don’t know whether the 1962 cars were modified with longer wheelbase. The first new car for 1963 was R6 which appeared in Austria in September.

I don’t understand mariner’s point (4) about the front rad area being changed to allow cold air to get to the Lucas “bomb”, the high pressure pump for the fuel injection. I thought that Lotus fitted the bomb at the back of the car, next to the gearbox. They may have moved it later but I couldn’t find any record of that.

 

I think the oil tank may come down to the constant development of the car. where there perhaps a few different versions? iv'e seen photos that look like most of the space behind the radiator is taken up by oil tank and I've seen an attempt at streamlining then I've seen an even more streamlined version. 

 

is the fuel bomb the cylinder I've seen mounted in front of the radiator in some cars? 

 

I'll have to track down that book Roger. Although since Amazon.com.au became a thing it's become more difficult and more expensive to find some books $400+ last time i looked at the John Tipler book. 

[Bikr7549]

According to Setright’s book (pg 125) Lotus moved the Lucas fuel pump to a position on the 25 in front of the radiator for the ‘63 East London race in SA. He doesnt mention where it was moved from.

[mariner]

I wonder if there is a single authoritative source on the 25/33 as its along time ago now!

 

However in the January 1966 Motor there was an interview with Colin Chapman on the development of the 25/33. As far as I know it is one of the very few  technical interviews given by Chapman. It was done by Charles Bulmer and ran to six pages. 

 

Now Chapman was noted for being economical with the truth when it suited him but since the  career of the 25/33 was over in 1966 there s no reason to assume he wasn't being open about the cars.

 

He confirms the injection bomb started at the back, overheated, was moved to the side ( which race guys?) then in front of the radiator. The fuel pipes were run outside in '65 due to the fuel in the tanks getting hot. 

 

He covers the many oil tank changes by explaining they were made due to design changes in the engine which used more oil etc.

 

In terms on gearboxes there were only 10 ZF boxes use in '61, '62, and' 63 for all the GP cars !. Finally ZF made improved versions for '64. 

 

My copy of that edition is falling apart I have read it so often but what is interesting for this thread is he confirms that only R10.R11 and R12 had the straight sided chassis' which were originally done to win back 2 gallons of tank fuel space lost in the design for the flat 16.

 

Just to add confusion Chapman never refers to a 25 or 33 but only to individual chassis numbers throughout the article!

Edited by mariner, 18 June 2019 - 08:22.

[Roger Clark]

The Chapman interview sounds very interesting. I liked the remark about the number of ZF gearboxes. I understand that it was not possible to changes ratios on these boxes they would just change boxes. With so few to choose from it must have helped to have a driver who could easily adapt his style.

As others have said, these cars.were clearly subject to continuous development during their career. I think it would be an interesting project to attempt to document those changes on a race by race basis. I have in mind a table with columns for event, driver, chassis, engine, gearbox and other notes and a row for each participation in a race. Much of this is already well documented in Theme Lotus, F1R and elsewhere but it is in the last column that we could add value by showing the development of the cars.

Would anybody be interested in helping with such a project, the results and work in progress to be posted here?

[Glengavel]

I was wondering, are the differences between the 25 and 33 more or less than the differences between the first and last 49, or 72?

[jeremy durward]

The Chapman interview sounds very interesting. I liked the remark about the number of ZF gearboxes. I understand that it was not possible to changes ratios on these boxes they would just change boxes. With so few to choose from it must have helped to have a driver who could easily adapt his style.

As others have said, these cars.were clearly subject to continuous development during their career. I think it would be an interesting project to attempt to document those changes on a race by race basis. I have in mind a table with columns for event, driver, chassis, engine, gearbox and other notes and a row for each participation in a race. Much of this is already well documented in Theme Lotus, F1R and elsewhere but it is in the last column that we could add value by showing the development of the cars.

Would anybody be interested in helping with such a project, the results and work in progress to be posted here?

 

I would be keen to help where I can Roger, although the fact that I posted this thread makes me think i won't be the most useful person for it. it would be interesting to see how the cars developed though. 

[jeremy durward]

I was wondering, are the differences between the 25 and 33 more or less than the differences between the first and last 49, or 72?

 

I think that's pretty spot on Glengavel, the 25/33 series of cars is unusual in that they felt the need to change the designation at all. I think Roger is correct in suggesting a table of developments and how they were implemented on the cars as there was no definite point were they change. 

[Doug Nye]

I was wondering, are the differences between the 25 and 33 more or less than the differences between the first and last 49, or 72?

 

Less.

 

DCN

[jeremy durward]

Less.

 

DCN

 

The more i look into it the more it seems the change from 25 to 33 designation was just arbitrary. the few things i thought were defining features of the 33 are nothing of the sort. I'm still intrigued about the changes that were made across the life of these car though. 

 

Are there any books that you would recommend on this subject?  

[Glengavel]

I suppose changing the number would make sense if Chapman was considering building cars for sale to third parties and trying to persuade them that it was new! improved! washes even whiter! etc., but as you say it does appear to be purely arbitrary.

[Roger Clark]

I was wondering, are the differences between the 25 and 33 more or less than the differences between the first and last 49, or 72?

Less than the first and second 72!

[Ray Bell]

The 49 came in B and C forms, IIRC...

And the 72 reached D before it was finally retired.

How many changes were made to the 49 because of the collapsing rear suspension? And it had a gearbox change, too, with serious redesigning of the sideplates after the French GP at Le Mans.

Of course, the wing era arrived when the 49 was at its height, so there were more changes just for them.

[Ray Bell]

By the way, where does the one-off '32B' chassis fit in this?

It always seemed strange that a 32 chassis would be the basis of a car with more power than the F1 25s and 33s.

[StanBarrett2]

The 49 came in B and C forms, IIRC...

And the 72 reached D before it was finally retired.

How many changes were made to the 49 because of the collapsing rear suspension? And it had a gearbox change, too, with serious redesigning of the sideplates after the French GP at Le Mans.

Of course, the wing era arrived when the 49 was at its height, so there were more changes just for them.

I seem to recall there was even an E version ?

[mariner]

I think an interesting discussion along the lines above is which cars were developed to keep up to date with outside changes and which were developed for extra speed regardless of outside changes.

 

In regard to Lotus's I would put the 25/33 in the former category. Almost all the changes listed by Colin Chapman in the Motor article were either driven by the engine,( injection, flat plane crank, oil consumption) , or smaller, wider tyres ( 13" wheels, longer swing arm lengths) 

 

In contrast the 72 underwent many changes with still the same DFV and same size tyres. Only at the end did the loss of the super soft Firestone's cause big( and not very successful) changes. 

 

The first 72 changes were drastic to get rid of the design mistakes like anti dive then, apart from the revised crush structures, the many changes were to get more chassis speed.

 

Of course all racecars go through many small changes to aid maintainence and reliablity

[Collombin]

I seem to recall there was even an E version ?

And an F - the long wheelbase version with the oil tank between the rear bulkhead and the engine.

I think the E was basically an elf'n'safety upgrade, with deformable structure panels.

[jeremy durward]

I think an interesting discussion along the lines above is which cars were developed to keep up to date with outside changes and which were developed for extra speed regardless of outside changes.

In regard to Lotus's I would put the 25/33 in the former category. Almost all the changes listed by Colin Chapman in the Motor article were either driven by the engine,( injection, flat plane crank, oil consumption) , or smaller, wider tyres ( 13" wheels, longer swing arm lengths)

In contrast the 72 underwent many changes with still the same DFV and same size tyres. Only at the end did the loss of the super soft Firestone's cause big( and not very successful) changes.

The first 72 changes were drastic to get rid of the design mistakes like anti dive then, apart from the revised crush structures, the many changes were to get more chassis speed.

Of course all racecars go through many small changes to aid maintainence and reliablity

Mariner, do you have a copy of the article you could send me?

Edited by jeremy durward, 22 June 2019 - 04:39.

[jeremy durward]

By the way, where does the one-off '32B' chassis fit in this?

It always seemed strange that a 32 chassis would be the basis of a car with more power than the F1 25s and 33s.

There’s the 39 to consider too isn’t there? It even had a chassis number in the 25/33 series.

How close was the 32 in design to the 25/33 cars?

[Ashley Lenton]

I always wondered if the rather spurious change in designation from 25 to 33 was not simply a ruse by Chapman to convince Esso that  he was not selling another team (Parnell) a "current" model. Shades of Walker and the 21.

[Ray Bell]

Tim mentioned the 39 in his first reply to the thread...

I've been trying to get in touch with Marc to get detail pics of those cars.

[jeremy durward]

I always wondered if the rather spurious change in designation from 25 to 33 was not simply a ruse by Chapman to convince Esso that  he was not selling another team (Parnell) a "current" model. Shades of Walker and the 21.

 

Ashley, can you expand on the Walker and the 21 comment? It's a car that seems to get ignored stuck between the 18 and the 24/25 so I can't say I know much about it.

 

Tim mentioned the 39 in his first reply to the thread...

I've been trying to get in touch with Marc to get detail pics of those cars.

 

Cheers Ray! look forward to seeing the photos.

[Ashley Lenton]

In 1960 Moss, in the Walker 18, won 2 GPs and the factory team none. Team Lotus sponsors were not pleased with a rival fuel company getting all the glory, so blocked sales of the new 21 -Walker only getting theirs when the season was over. Hence the Walker/BRP "18/21" initiative- old cars updated where possible. Presumably Esso knew the 25 was imminent in 1962, so did not object to other teams having the 24. 33 R8 that was sold to a private team in 1965 had a suspect chassis, and Clark refused to drive it.

[Roger Clark]

There’s the 39 to consider too isn’t there? It even had a chassis number in the 25/33 series.

How close was the 32 in design to the 25/33 cars?

The 32, in its F2 guise was very similar the 25.  It was derived from the 27, the 1963 Formula Junior car.  The monocoque looked slimmer than the 25, presumably because less fuel was required.  The 4-cylinder engine meant that it was not necessary to reduce the height of the monocoque around the engine bay.  The suspension followed the general lines of the 25; the upper rear radius arms were attached at the top of the hub carrier like the 25B or 33.  The gearbox was a Hewland, as used in the Formula Junior cars.

 

The 32B had suspension and transmission beefed up to cope with the increased power.  An HD Hewland gearbox was fitted.  The monocoque around the engine bay was removed and replaced by a tubular structure.

[D-Type]

~ It [the 21] is a car that seems to get ignored stuck between the 18 and the 24/25 so I can't say I know much about it.

 

The 1961 20 Anglia-powered FJ car and the 21 Climax 4-cylinder F1 car were derivatives of the 18.  They were slimmed down as much as possible and introduced the "semi-reclining" driver - all measures to reduce frontal area and improve airflow.  The 22 was the updated version of the 20 FJ car for 1962.  The V8 Climax wouldn't fit into the chassis of the 21 which led to the 24 which was essentially an enlarged 21.  Then the 25 was the first "monocoque".

[Doug Nye]

I have kept out of this discussion thus far - since the last thorough investigation of this topic just about blew what's left of my mind.  

 

However, our GP Library has just acquired the photo archive of our long-time friend and colleague Graham Gauld.  And within it we have found this long-forgotten gem. A painted-on chassis number...

 

And, in passing, some might perhaps study the monocoque formation visible here...and discuss?

 

][/u

 

Photo Copyright: The GP Library

 

DCN   

Edited by Doug Nye, 23 June 2019 - 12:33.

[D-Type]

Hmmmmm.  My first thought is that the painted on number is for carnet purposes to discourage customs officials from looking further.  Or am I being overly cynical?

[Ray Bell]

We've come all this way and that's the first pic in the thread...

Well, here are two more:





Taken after Leo's Bathurst crash by Lance Ruting, now on Autopics.

[Ray Bell]

Originally posted by Roger Clark
.....The 32B had suspension and transmission beefed up to cope with the increased power. An HD Hewland gearbox was fitted. The monocoque around the engine bay was removed and replaced by a tubular structure.

Sorry, Roger...

No tubular structure. The monocoque went to the rear suspension.

And I know there were LOTS of rivets in that chassis.

I guess the fitment of the engine differed from normal FPF installations because of the restrictions of the monocoque, the engine was either upright or more upright that usual.

[JtP2]

32B = Tasman on the cheap? Was there good starting money?

 

I was digging out articles on 25/33 for some one recently. There is discussion in period (very old articles) about ZF gearbox problems and gear selection difficulties being put down to swarfe in the boxes. Clark's Monaco 63 being attributed to this, but it would seem to me to be a missing detent plunger. Thoughts/ further info?

[Roger Clark]

Sorry, Roger...

No tubular structure. The monocoque went to the rear suspension.

And I know there were LOTS of rivets in that chassis.

I guess the fitment of the engine differed from normal FPF installations because of the restrictions of the monocoque, the engine was either upright or more upright that usual.

Sorry about that.  My source was Theme Lotus which I normally consider reliable.

[StanBarrett2]

We've come all this way and that's the first pic in the thread...

Well, here are two more:





Taken after Leo's Bathurst crash by Lance Ruting, now on Autopics.

Is that Geoghegan's 39 Repco

[Glengavel]

Sorry, Roger...

No tubular structure. The monocoque went to the rear suspension.

And I know there were LOTS of rivets in that chassis.

I guess the fitment of the engine differed from normal FPF installations because of the restrictions of the monocoque, the engine was either upright or more upright that usual.

This article here:

https://www.sergent....tor/tas65p.html

implies that the engine was held in a space-frame.

Jim Clark was entered by Colin Chapman in a special Lotus 32 based on a F2 27/32 monocoque but with a spaceframe rear to house the Climax FPF, which left the whole car only 8 cm longer than the F2 version. The engine in Clark's Lotus was, in fact, a reduced 2.7 bought from Innes Ireland and this was mated to a ZF gearbox.

 

I wonder if Innes pee'd on the FPF...

[Catalina Park]

There is an interesting photo at Primotipo...

https://primotipo.co...w-zealand-1965/

[Catalina Park]

Autopics has this as well..
http://autopics.com....-wells/#gallery

Edited by Catalina Park, 24 June 2019 - 07:04.

[Roger Clark]

It is also clear in the photos linked to by Catalina that the car has a ZF gearbox, not a Hewland as I said.

[Roger Clark]

I have kept out of this discussion thus far - since the last thorough investigation of this topic just about blew what's left of my mind.

However, our GP Library has just acquired the photo archive of our long-time friend and colleague Graham Gauld. And within it we have found this long-forgotten gem. A painted-on chassis number...

And, in passing, some might perhaps study the monocoque formation visible here...and discuss?

][/u

Photo Copyright: The GP Library

DCN

Straight internal sides to the monocoque? I find it difficult to tell. Innes Ireland drove R7 five times in 1965, the last in the non-championship Enna race. At the Italian Grand Prix he switched to the new R13.

You can also see that the bodywork has a bulge, presumably to allow room for the drivers hand when changing gear. Parnell adopted that early in 1965.

[Ray Bell]

We know Clark had two engines, so to say that the engine was a specific engine is fraught with difficulty...

The 39 certainly had a tubular rear section, it distinguished the car from the other Lotuses we saw at that time.

[Paul Hamilton]

The late John DD was a good mate of mine and I was very familiar with his 25, 32B and the 39 during his ownership of them.

The 32B had a full length monocoque tub extending to the rear bulkhead on which the gearbox was mounted. That imposed space restrictions which required a vertical mounting for the FPF engine rather than the inclined installation typical of other Tasman cars from the period. The 39 tub ends at the rollover bar bulkhead immediately behind the driver with a tubular and steel sheeted subframe extending rearwards beyond that to provide mountings for the gearbox, suspension and an inclined FPF engine. The subframe is a fixed element integral with the main frame rather than a demountable structure such as used in many other semi monocoque cars such as March, Chevron etc.

I never had the opportunity to drive the 32B but spent some time at the wheel of both the 25 and the 39. Although I am of average height and build both were very tight fits for me and I think it’s probably true to say that their cockpits were designed around JIm Clark dimensions.

John’s 25 is now owned by Sydneysider, John Bowers. He leaves it in the care of Classic Team Lotus who have run it in Europe and the UK with great success for some years now driven by Andy Middlehurst. CTL also have custody of the 32B following a deal DD did to exchange it for a type 79. The 39 is in the hands of Chas Kelly in Tasmania but it has not been used in anger since he acquired it at the auction of the DD collection.

[jeremy durward]

I have kept out of this discussion thus far - since the last thorough investigation of this topic just about blew what's left of my mind.  

 

However, our GP Library has just acquired the photo archive of our long-time friend and colleague Graham Gauld.  And within it we have found this long-forgotten gem. A painted-on chassis number...

 

And, in passing, some might perhaps study the monocoque formation visible here...and discuss?

 

][/u

 

Photo Copyright: The GP Library

 

DCN   

 

Well that's a kinked chassis isn't it with the gear lever placed where it is, which makes sense for R7. Is that normal reinforcing around the the hole for the gear lever?

[jeremy durward]

We've come all this way and that's the first pic in the thread...

Well, here are two more:





Taken after Leo's Bathurst crash by Lance Ruting, now on Autopics.

 

So looking at this while the 33 had moved to straight internal sides this car was built with the kinked internal sides. Is this a move back to the old style of chassis? or was this built before the straight internal side chassis? despite what chassis numbers would lead us to believe. 

[mariner]

Going back to the 32 for a minute it was indeed a development of the 27 FJ car. The 27 was another example of Chapman trying to be a bit too clever to make a profit on seliing race cars ( like the 30). 

 

The 27 started with a glass fibre outer curved monocoque with only the inside panels in aluminium. The glass fibre was curved when moulded saving the need to form the outer panels by hand. Unfortunately attaching the GF to  aluminium by rivets sort of ignored the soft nature of GF so the  whole chassis flexed worse and worse as the fatigue loads opened up the GF rivet holes etc.

 

So the 32 used alloy throughout.

 

I terms of why the 32B was use for the  2.5litre Climax 4 in Tasman , to save weight as the races were short heats and fuel capacity required was low. Bruce McLaren did that first with his ultra slim Tasman Coopers. 

 

Also I suspect the available 25/33's were needed for F1 

 

The "small Tasman" theory showed up again when Team Lotus took the  49's with 2.5litre DFV's down under. IIRC Chris Amon go very competitive with them running a smal F2 Ferari with ex GP sized 2.5 litre V6.