Brooklands Bentley

The next step on the bodywork journey is making the cowling. This is an important structural section as it provides support for the bonnet sides and starts to set the shape of the passenger compartment. Whist it does not structurally support the steering wheel in this car, it may provide support for the dashboard, depending on how I decide to mount it.

On the original cars the dashboard follows the cockpit and blends in to the trim that follows the cockpit around to the rear. It is very well executed and something that I would love to replicate, but may not be easy to do.

I suspect that I will end up blending the bottom corners of the dash into the cockpit but will try to follow the shape if I can.

The cockpit itself has a distinct opening shape that is angled to the bottom of the dash and then sweeps back and down towards the rear. This angular opening is another one of the characteristics I am keen to replicate.

The other characteristic is that the cowl is relatively long. Most cars of the era have a long bonnet and a short cowl, but the Bentleys had a long cowl and a long bonnet.  This proportion of bonnet to cowl is another thing to try and capture.

So I decided that the best way to make the cowl was to simply fold a sheet over the A-pillar hoop - setting the front of it in approximately the right position, and then eventually cutting the cockpit shape at the rear. 

But the problem that I found was that the blanks I had cut were too small to reach all the way to meet the rocker. Stopping some 100mm short. 

This is an issue of my own doing. I purchased a full sheet and then had it cut into 1200 x 600mm pieces so that I could fit it in the car, thinking that they would be ample. But I guess that's just not my luck lol. So I need to go back to the drawing board with how I make the cowl. 

One option would be to make it in two halves and weld them together right in the middle. This may actually be of benefit as it would be easier to put some shape into the cowl where it flicks up at the cockpit opening. 

The other option is to weld on the extra 100mm of material and then shape as one panel. This has the advantage that the front edge can then be rolled in one continuous profile, rather than attempting to weld it, which I suspect will be a PITA.

So no easy choice and no clear winner. Maybe options 3 is go buy more ali, but I'd rather not and it's got to be welded anyhows so in for a penny - in for a pound.

And that's as far as I have got with the cowl so far. Two steps forwards and one step backwards. I'm beginning the realise, that's just how I roll. :D 

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Today I decided to make a start on the belly pans.

Some may note that Most Bentleys did not have belly pans / rocker trim. They simply ended at the bottom of the chassis rails, with all of the guts beneath on show.  

My build is based on 'Old number 1', the Bentley that won Le Mans twice in a row and the Brooklands 500 twice. A car that was modified many times over the years, including the addition of rocker trim that folded under the car to give a more streamlined look.

I decided to try to replicate this look by forming the bottom frame hoops to replicate the rolled rocker look of Old number 1. And so today I attempted to skin them with steel.

I decided on steel for the bottom to give it some strength. Using steel I could weld it directly to the chassis making it nice and solid. Of course it adds a bit of weight, but then the originals were over a ton and a half. I'm not planning on breaking any records. lol.

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After clamping a sheet of steel to the chassis attempting to form it over the rocker hoops two things became clear. The join in the middle of the underneath needed to be reinforced, and the rockers hoops tapered towards the front.

So the solution was to roll the steel the opposite direction - from the bottom to sides. To address the reinforcement issue I decided to weld some additional supports in the centre of the floor between the hoops. 

So with the additional supports in place, I could now tack the sheet in position and work my way outwards, forming the sheet as I went.

With the sheet formed around the rocker hoops and clamped in position, I used a straight edge to mark where the sheet needed to be cut. Originally I had hoped that the cut would be underneath, but to get the sheet to follow the rocker hoops I needed to start from the bottom.

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After cutting the sheet I tacked the bottom to the frame and formed it around the rockers.

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 I unfortunately blew a couple of holes, so had to patch those up, which will need dressing back before paint. An unfortunate side effect of welding upside down at arms reach without my glasses on. lol.

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​The day ended up getting away from me so I only got one side done. Although I did spend some time welding up the frame which was only previously tacked together. The rest of the time was spent looking for an imperial allen key and looking for my old welding helmet, which I never did find. How I can misplace such a thing I don't know. It is something I need to find as I don't want to ruin my TIG helmet with nasty MIG spatter.

I took a look at radiator badges but at $400 for a reproduction, it's not something that I'm ever likely to buy

so after a bit of digging, I managed to find a 3D model for one. I actually think it might be a more modern version, but as the design has not changed much in 100 years, it will do fine.

Whilst it isn't shown in the image above, there is also an insert with the Bentley B on it that is part of the model

​I printed out a couple of different versions on my FDM printer but the quality just isn't there. (and I cannot be arsed to hand finish them - far too much work and a PITA for someone who should wear glasses but refuses to )

I've considered printing one with my resin printer and painting it, but then I remembered that a while back I bought an electric ladle and some pewter to make a badge for another project. A metal badge would definitely be better than a plastic one.

The process is essentially to make a silicone mold from an existing badge using castable silicone, then use it to cast a new badge in pewter. The silicone can grab really fine details and will not melt from the heat of the pewter.

I figure that I can resin print the master and then take a mold from that which I can then cast the pewter in. A bit of a protracted process, but then I'm in this for the journey as much as anything else.

For the centre I think i will cast a laser cut B in some clear resin and cast it in the centre. This technique works really well. I used the same process to make a horn push for the Speedster. I took a silicone mold of the original horn push and then cast a new one up setting a Porsche pin badge in the centre. As you can see the finish is just like glass.
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Of course I'm probably getting way ahead of myself, as there's plenty more things to be doing, but it keeps me out of trouble. 

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Sketched out the bottom panel for the radiator in Fusion 360 and cut the panel out on my CNC plasma. All was going great until the plasma decided to trip out and no matter what I tried it would not reset.

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So I had to hook up the new plasma on a temporary supply, which was, erm, lets say a little interesting. Cable was definitely under-sized and it definitely got a bit warm. Wiring up the new plasma is one of those jobs that's been on the to-do list for at least 12 months, along with upgrading the X-Y motion. But as with all things, something else always seems to get in the way. Such is life.

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So I finally managed to cut the part out. It has a bit of a gnarly bit where the old plasma tripped and I had to re-run the job to continue on, but nothing that cannot be cleaned up with a little time.
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I need to add more of a bend into it as it does not follow the shape of the top part of the surround, but to do this I'll need to move the blower forwards (It's only tacked in place).

Also managed to find some cheaper grille mesh. It's not quite as chunky as the other stuff I found but is a little more palatable price-wise. Just need to order it.

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Type / for commands...

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So spent today fettling and welding and managed to get the radiator shell to the point where I can move on to the next item. It's not 100% finished as it needs planishing and trimming but the shape is kinda there and it's all in once piece.

So the first order of business today was shaping the side panels. These had a fair bit of crown to the 'shoulders' and required both raising with the blocking hammer and shrinking with the tucking fork.

I think that ideally the shape would be split between the top panel and the side panel, but as the pattern was not ideal most of the shape ended up at the top of the side panel.

Welding

TIP: You cannot use a MIG welder when metal shaping as the heat-affected-zone (HAZ) of the weld is too hard to planish or file. You must use TIG, or preferably oxy-acetelyne.

• Clamp the panel at one end of the weld making sure that the panels are aligned.
  
• Make a small tack weld
  
• Allow to cool
  
• You will see that the ends of the panels are pulled together (see image above). This is due to the HAZ cooling and contracting causing the join to distort.
  
• Using a hammer and dolly planish the weld (just two or three sharp taps right on the weld is usually enough). If it is a small panel you can flip it over and use an anvil or flat top part of a vice as the dolly. This saves needing a third arm or an accomplice.
  
• Planishing the weld releases the tension from the HAZ and allows the panel to re-align (see image below)
  
• Continue on in this manner with tacks approx 1" apart until the panel is completely tacked.
  

• Once the panel is completely tacked up, you can then go back and weld in between the tacks.
• Be careful when welding near to the edge of the panel as it is easy to put too much heat into it causing the edge of the metal to melt back. You can prevent this by using a copper heat-sink. A flattened piece of copper pipe makes a great heat-sink. Just clamp it to the backside of the panel. The weld will not stick to the copper. (you can also fill holes using the same method)
  

One side down, one to go...

So with one side welded together I trimmed back the inside corner to blend a bit better and offered it up on the car. I also trimmed the bottom to fit over the chassis rails. 

I then spent some time filing the weld to blend the panel together. This still needs some further planishing and sanding which I'll do when i do the final finishing.

With one side down I set about replicating the same shape in the opposite side panel. This did not take too long as I just went hard at it replicating the same blocking and tucking that I had done on the first side, dispensing with the many trail fits and fettling I did first time around.

Offering up the panels I scribed the panel joins as there was a little overlap. I then trimmed the panels to suit before welding the side to the top and then the two halves together. 

Finishing touches

No radiator would be complete without a radiator cap. I tried a few different bits of pipe and other things I had laying around, but nothing looked quite right. So a quick scavenge through the parts bin turned up an old VW fuel filler cap from my speedster project. I had kept the cap and filler neck which I had cut off to fit a flip top style filler cap

It's been a long time since I did any work on the Cyclekart. The house build is still ongoing, I still haven't got the roof on the carport and work has a tendency to consume unreasonable amounts of time. So any plans that I put in place to do work on the Cyclekart always seem to get pushed aside at the last minute when something more important crops up.

So with the upcoming Yesterdays Power Rally event coming up next weekend, I thought that it was about time I thought about putting some bodywork on the Bentley and so have blocked the entire week out to work only on the cyclekart.

First order of business

So the first thing that I wanted to do is to get the radiator surround sorted. It's definitely the most complex part of the bodywork and maybe the most important, as it sets the entire aesthetic of the car. Get it wrong and it won't look like a Bentley. 

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Differences

The SS Jag surround is a little different to the Bentley surround in that it folds back under itself to form a recess where the grille mesh sits, whereas the Bentley has a trim attached to the front which protrudes outwards. 

After adding some shape to one of the top parts and test fitting, it was apparent that the angled part of the pattern,  which would normally tuck back on itself to form the lip at the centre was not going to work.

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Moving Metal

I added some crown to the panel using a blocking hammer. An interesting technique which looks like you've ruined the panel...

But is easily rolled out using the english wheel....

TIP: The trick here is to 'trap the tuck' by hitting the 'root' of the fold. This captures the top of the 'pleat' and then allows the remaining metal along the pleat to be planished into itself, 'shrinking' the metal along the edge. It's a simple technique which anyone can do using a home made 'tucking fork'.

Thoughts and contemplations

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