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Howmet TX, Le Mans 24h 1968


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I was about to start the 1924 Alfa Romeo P2, but realised I needed to think a little more about replacing rivets, so @Malc2, you are lucky, here is the Howmet TX!

 

The Howmet TX is known for the implementation of a turbine engine in endurance car racing in 1968. It wasn't the first turbine powered race car and the project suffered problems, but it's still regarded as probably the most successful, even with race wins to its credit. The cars featured a one speed gearbox and an ingenious waste gate system to minimize the turbine throttle lag and improve driveability. A small electric motor made up the necessary reverse gear. Luckily there are Howmets competing in historic racing today, albeit using a slightly different turbine but the same technique, so we can share a bit of the experience. It's quite a different sensation from ordinary race cars. Enjoy!

 

 

 

Le Mans 24 hours should have been the high light of the Howmet TX project, but as the saying goes; Le Mans is a tough mistress, and it was not to be success. #22 suffered fuel problems right from the start and could only manage some 70% of full power and in the evening it crashed out of the race. #23 suffered a wheel bearing failure in the second hour requiring a three hour pit stop for repairs, which lead to a disqualification after seven hours for not covering the sufficient distance. Not a good weekend to say the least. But still, Le Mans is Le Mans and so worthy of having models built.

 

So I will build the recent 1/24 scale resin kit from Profil 24 as one of the two Le Mans 24 hr entries of 1968, #22 or #23, the kit covers both. Hmm.

 

TX1.jpg

 

The kit comes with some complex engine and transmission detail, which should make an interesting build and scope for some added detailing. There are quite a lot of resin parts, in need of various degrees of cleaning, filling and preparation.

 

TX2.jpg

 

TX3.jpg

 

Two sets of vac forms, lights, belt material, photo etch and decals. Yes, Ford Cortina MkI rear lights.

 

TX4.jpg

 

And a few pages of drawn instructions. Reference (period correct) photos of the engine bay will hopefully fill in where the instructions look a bit vague at this early point.

 

TX5.jpg

 

Serious work started yesterday morning, but I have spent some weeks with research before that, and research proves to be valuable with the Howmet TX, as we shall see. If you are easily bored by long rants about odd details I'm sorry.

 

Two chassis were built by McKee Engineering for the 1968 season. The first chassis, usually called GTP1, wasn't built from scratch, the frame for it came from the piston engined 1966 CanAm car McKee Mk6/3 and was adapted for its new role as GTP1. The second chassis, GTP2 or TXGTP2, was purpose built for the TX turbine project and got a 2 1/4" longer wheel base. In later years McKee has built two more TX chassis, GTP3 and GTP4, so today there are more Howmet TX's around in the historic scene than in 1968, but for this build the two original chassis will cause problems enough.

 

GTP1 with wheel base 91 1/4", (2318 mm or 1/24 96,57 mm) was #23 at Le Mans.

GTP2 with wheel base 93 1/2", (2375 mm or 1/24 98,95 mm) was #22 at Le Mans.

 

The kit comes with one body/chassis and decals for both cars. 2 1/4", 57 mm, gives 2,38 mm difference in 1/24. That's enough difference to be noted and cause concern if you want it to, and not enough difference to bother about if you don't want to. I wondered about the kit parts and measured the chassis wheel base to about 98,5 mm. So pretty close to GTP2 #22. The chassis wouldn't really fit into the body shell properly at that point as both needed a good deal of cleaning up, but it all looked OK for #22.

 

By the time of that discovery I had been leaning towards #23 for the build due to its added orange patches for the Le Mans race. So I spent some hours studying all reference photos I could find to determine where the cut would have to be made to shorten it, to see what problem that would cause. That proved a lot harder to find out than expected, and I'm still undecided about it. But when looking at all photos back and forth #22 perhaps looked better without that orange patch on the nose, so somewhere there I started cleaning up the body shell and the chassis part yesterday morning for GTP2 #22.

 

It took a bit work with quite a lot of air bubbles at the front of the chassis part, but after a while it all looked good. As separate parts.

 

TX6.jpg

 

TX7.jpg

 

When the chassis started entering the body shell as it should the front wheels would line up fine under their arches, but the chassis didn't appear to line up well further back.

 

TX8.jpg

 

This picture doesn't show it well as the camera perspective distorts things, but sure enough the rear wheels were at least 1,5 mm too far back in the chassis part.

 

TX9.jpg

 

To get the body shell onto a set of wheels quickly for measuring I borrowed a set from a Fujimi Ford GT40 MkII. It's easy to think they were the same wheels, but they were not. The front tires are also a little too large for this model, but for measuring they were fine. The body shell wants to have about 97 mm wheel base, 1,5 mm shorter than the chassis.

 

TX10.jpg

 

As it appeared I had a GTP2 #22 chassis and a GTP1 #23 body shell. And no, there are not two different kits made for the two cars. It was clear some cutting would have to be made. So I went back into research mode with the resin body in front of the screen with reference photos floating around, trying again to find where the difference in length was to stretch the body shell for #22.

 

Suddenly I see that the right side fuel cap have a different angle on the two cars, the resin body is closer to #23. Then the obvious thing, that I had completely missed, stared me in the face. The two cars had different roof sections with the doors differently hinged. GTP1 #23 had the hinges outside of the centre section with its air scoop and the bulge in front of it. GTP2 #22 had the hinges close to the centre with the doors going round the air scoop and the bulge cut in three sections.

 

TX_ref_1.jpg

 

To add further confusion GTP2 #22 was the car that crashed out of the Le Mans race with substantial body damage. After Le Mans Howmet folded down its racing programme and the GTP2 chassis was rebuilt with a flat low open roadster body for turbine speed record attempts in 1970. Years later it was rebuild back to Howmet TX configuration, but now with a roof section and doors hinged like GTP1...

 

The roof section of the resin body shell is GTP1 #23, no question, and it matches the shorter wheel base. It could of course be modified for GTP2 #22, but that would still leave the question of where to cut and stretch to body. My thoughts went back to building #23. The chassis had to be cut and shortened. It would be the easy way out. To determine where to best place the cut I fiddled around with the main parts to see what may become a problem later on.

 

TX11.jpg

 

Interestingly enough the rear fire wall in the cockpit, which has mounting tabs inside the body shell, ends up at least 1,5 mm in front of the wall section moulded with the chassis. That's where I placed my cut. The seats would still fit nicely. Hopefully the only other thing that can cause problems later on is the air channel between the roof scoop and the turbine itself. If so I'll deal with that later. But there may well be other problems due to this action. We'll see what happens.

 

TX12.jpg

 

I did just one cut in the middle of my markings.

 

TX13.jpg

 

Then I sanded the cut surfaces to a good fit and the desired length. I set my goal at 96,7 mm something.

 

TX14.jpg

 

With the two halves CA glued together on the flat work bench I cut four pieces of metal rods, then used the Dremel to grind a slot for each, ditched the metal rod into the resin dust, filled with CA and more resin dust.

 

TX15.jpg

 

With the slots filled and everything sanded smooth I had a strong and shorter GTP1 chassis.

 

TX16.jpg

 

It now fits the GTP1 body shell quite well. #23 it is.

 

TX17.jpg

 

And the rear wall now lines up perfectly with the lower section. Thanks a lot.

 

TX18.jpg

 

With this confusion in my head finally (?) sorted and the main parts brought to some sort of agreement it's now time to clean up and prepare all the other resin parts.

 

I just can't completely put to rest where to stretch the body for GTP2 #22... If it's even only in one place...?

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Oh boy, am I so looking forward to this!

Thanks Jörgen, the kit parts look great. (Edit - Although I have now read through your comments!)

Helpful comment (not) No1 in a series..............

Because the engine and trans are so unique, I would be tempted to copy and display them alongside the completed car.

 

M.

Edited by Malc2
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15 minutes ago, Malc2 said:

Oh boy, am I so looking forward to this!

Thanks Jörgen, the kit parts look great. (Edit - Although I have now read through your comments!)

Helpful comment (not) No1 in a series..............

Because the engine and trans are so unique, I would be tempted to copy and display them alongside the completed car.

 

M.

Thanks a lot. The parts so far are looking good indeed, they are just a bit in confusion which chassis they want to become 😎

 

4 minutes ago, Sabrejet said:

Nice work: I bought this one when it was issued but have yet to build it. Watching with interest!

Many thanks. Mine is also from the first batch, it's been in the stash waiting. It would be nice to see GTP2 #22 properly built, if we can determine the cuts... 😎

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3 minutes ago, Bengalensis said:

Many thanks. Mine is also from the first batch, it's been in the stash waiting. It would be nice to see GTP2 #22 properly built, if we can determine the cuts... 😎

 

I've seen Howmets a couple of times and I know that at one point one of the cars ran with a different engine (in recent times). I've looked into them a bit but didn't realise that the two cars were different lengths.

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Another interesting project which I'll enjoy watching you work your magic on, a type I've not heard of before.

 

   Stay safe               Roger

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15 hours ago, Sabrejet said:

 

I've seen Howmets a couple of times and I know that at one point one of the cars ran with a different engine (in recent times). I've looked into them a bit but didn't realise that the two cars were different lengths.

The difference in length between GTP1 and GTP2 have been surprisingly difficult to pin point. I would think the two newer chassis GTP3 & 4 are built as copies of the longer GTP2, but I'm not sure. As I understand they are all using a slightly different turbine these days as the original isn't available since back then. The exhaust layout is different today with the two pipes coming from further forward to reach the back of the cover and the smaller waste gate pipe exiting in the centre. I'm not sure if all cars have been rebuilt that way today, or if one of them is still using that newer turbine without the waste gate and the two exhausts right through the top of the engine cover.

 

15 hours ago, Hamden said:

 

Another interesting project which I'll enjoy watching you work your magic on, a type I've not heard of before.

 

   Stay safe               Roger

Thanks a lot Roger!

 

13 hours ago, galaxyg said:

Interesting looking car and project.

Thank you very much!

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The fit of the engine cover needed attention.

 

TX19.jpg

 

Some hair dryer heat, reshaping, sanding and a little added material sorted it out without too much trouble. I also thinned it down to maybe half the thickness.

 

TX20.jpg

 

With all wheel parts finished up came the all important first set up to ensure it will work out later on. After a little bit of reshaping to the rear wheel arches I had this walk around look with a wheel base of 96,7-96,8 mm and loosely fitted wheels. I think I can work from this later on.

 

TX21.jpg

 

TX22.jpg

 

TX23.jpg

 

TX24.jpg

 

TX25.jpg

 

TX26.jpg

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Another resin building masterclass... that's good technique there, with the re-joining of the chassis parts... nice work!!

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Superb job as usual Jörgen.

The low angle walk around shows what a brutal and purposeful looking car it is.

The in car video was interesting, you can clearly see that the driving style has to be adapted to suit the power delivery due to the CVT like throttle response!

 

Malc.

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5 hours ago, Alan R said:

What a wonderful beast!

I just love the Mk 1 Cortina tail-lights....

 

 

Cheers,

Alan.

It really is, and it's growing as I work on it.

 

It's hard to go wrong with Cortina rear lights on a classic design. Here on the Lola GT 1963 😎

 

TX27.jpg

 

3 hours ago, JeroenS said:

Another resin building masterclass... that's good technique there, with the re-joining of the chassis parts... nice work!!

Thanks a lot Jeroen. +30 years of messing with resin should leave some trace 😎

 

2 hours ago, Vesa Jussila said:

Interesting project again. Need to follow this too. 

Glad you think so Vesa, always nice to have you along!

 

2 hours ago, Malc2 said:

Superb job as usual Jörgen.

The low angle walk around shows what a brutal and purposeful looking car it is.

The in car video was interesting, you can clearly see that the driving style has to be adapted to suit the power delivery due to the CVT like throttle response!

 

Malc.

Thanks Malc, especially glad you like.

 

Yes, the driving style is interesting, it clearly has to be treated for what it is and the references become quite different. I really like that there are people who have gone through all the extra trouble to bring these back to the historic racing scene, instead of being silenced in some museum.

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As I started work on the engine and transmission parts it soon became clear that some more work would be needed. Part of this is due my shortening of the chassis, but far from all of it. It's a challenge and it will be fine.

 

The gearbox lines up quite well with the suspension uprights, but it now sits just a little too far in when seen from behind, and with the turbine placed as intended on top of it the exhausts are now a little too far forward. So after some internal debate I placed new mounting pegs on the chassis, moving the gearbox a mm or slightly less backwards. The drive shafts still fits OK.

 

TX28.jpg

 

There is a large gap between the fuel tank and the cockpit wall. This only partly due to my cutting, the gap was large even before.

 

TX29.jpg

 

The turbine is blue tacked to the gearbox. The rear wall of fuel tank lines up ok with the turbine, but there is not enough room to fit what I believe is the electric reverse motor to the transmission front. The air intake needed a little work and its mounting flange on the turbine was thinned down to make it an ok fit to the roof scoop of the body shell.

 

TX30.jpg

 

With the engine cover on the exhaust pipes now exits nicely.

 

TX31.jpg

 

There is only one small mounting point at the rear to fit the turbine to the transmission. I needed something more reliable to do repeatable test fitting. A piece of styrene rod and a drilled hole was the solution.

 

TX32.jpg

 

Something like this.

 

TX33.jpg

 

The reverse motor was shortened a little bit to clear the fuel tank, and the tank itself got some styrene strips added to bring it closer to the wall. More work is needed on that. The waste gate with its pipes has also been added. Further work on all three pipes with more hollowing out and thinning will follow later.

 

TX34.jpg

 

I get the impression from reference photos that the rear opening of the engine cover was not symmetric; on the left side the opening looks squarer to leave room for the waste gate pipe. I started similar work.

 

TX35.jpg

 

Some more dry fitting. Next I must finish the fuel tank with its two filler pipes.

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Great to see you starting the Howmex.  Like several others, I didn't realise the differences between the two Le Mans cars.  Great job on shortening the chassis, BTW.

There are some very good photos of the cars at Le Mans in the Joe Honda Sports Prototype book number 14, (1968 part 2).

Trevor

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20 hours ago, Flintstone said:

Great subject and a great model of it! I have seen the Howmet at Goodwood, but which one as I was not aware there are now four? 

Thanks a lot! It sometimes gets complicated in the historic racing scene...

 

9 hours ago, Hamden said:

 

Nice progress on this unusual car

 

  Stay safe              Roger

Thanks a lot Roger!

 

8 hours ago, klubman01 said:

Great to see you starting the Howmex.  Like several others, I didn't realise the differences between the two Le Mans cars.  Great job on shortening the chassis, BTW.

There are some very good photos of the cars at Le Mans in the Joe Honda Sports Prototype book number 14, (1968 part 2).

Trevor

Many thanks Trevor. I didn't know much about this either before I started reading myself up in preparation for the build. It's amazing how individual the cars could be in the same team back then.

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Oops, I forgot this photo yesterday... Nevermind, here it is:

 

TX36.jpg

 

The core of the modified fuel tank was sanded smooth and was blue tacked in place, and then it was time to fit the filler pipes. I made new pipes from some old styrene sprue as the resin parts were a little short in my application.

 

TX37.jpg

 

The finished fuel tank ready for primer and paint.

 

TX38.jpg

 

The rearmost extension of the chassis framework glued in place. The two joints were reinforced with thin metal pins. It's still a fragile assembly at this stage.

 

TX39.jpg

 

The rear end of the transmission needed a little improvement. There are two thin photo etched discs supplied to represent the two belt pulleys, but a bit more substance is needed I think, and the lower one was raised a little. The top pulley would need to be raised somewhat as well but I don't want to rearrange the whole rear section, so this will be the compromise. After some paint the photo etch parts will be fitted on top of this.

 

TX40.jpg

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4 minutes ago, Malc2 said:

Looking good, that rear push bar(?) does seem very vulnerable!

 

M.

Yes, hopefully I will be able to fit the two diagonal bars going up to the towers for the top rear spring mounts, when those are put in place. I just hope there will be room enough...

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This is not a straight forward build, I'm quite sure that has become clear. Every part around the back end needs some careful thinking through, tweaking, filling, adapting and so on. I'm pretty sure it will pay off in the end. Today has seen a little more progress.

 

The springs on the shock absorbers had much air in them and could not be cleaned up properly. I shaved them all off and wound some rounds of lead wire to replace. It can be quite simple as all the suspension parts really need to do is to create an acceptable view through the open rear end; they are pretty much shielded by aluminium panels when the engine cover is lifted.

 

TX41.jpg

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