Mercedes-Benz W165 Grand Prix engine in 1:3 scale

[Zephyrin]

one of the things that intrigues me about these incredible engine models is the way you move forward...
are the parts for the different cylinders all interchangeable, or are they individually identified for assembly and reassembly? that's some complex marking !
and on the other hand, to add the pumps, for example, are the fixing holes already provided for in the design, or do you have to dismantle part of the engine to drill and thread them, (the way I proceed usually "mutatis mutandis" obviously) ?

a name comes to mind for the sword of your valiant knight, "excalibur".

[fumopuc]

Hi Mike,
good to know, that your fantastic work will be permanent watched and is under a safety control now.
As Kim mentioned already, not easy to recognize, that we have a model engine here at the garden table.
For me it looks always like the real one.

[Art K]

Mike,
Amazing detail and workmanship. If I recall I have the internals of a Ford 2.3 liter oil pump on a book shelf. I somehow got behind in this build and relaxing after breakfast doing some catch up reading.
Art

[Vixen]

one of the things that intrigues me about these incredible engine models is the way you move forward...
are the parts for the different cylinders all interchangeable, or are they individually identified for assembly and reassembly? that's some complex marking !
and on the other hand, to add the pumps, for example, are the fixing holes already provided for in the design, or do you have to dismantle part of the engine to drill and thread them, (the way I proceed usually "mutatis mutandis" obviously) ?

a name comes to mind for the sword of your valiant knight, "excalibur".

Hello Zephyrin,

All the smaller parts on the cylinders should be interchangeable (I try to make them identical) but I prefer to leave the parts in the same position. Things like the camshaft bearing caps are all number stamped to show their location and orientation. The cylinder blocks and cylinder heads on each engine are handed (left bank, right bank) but could be interchanged between the two engines.

Wherever possible, I drill and tap ALL the holes when a part (such as the crankcase) is being made. The holes are all accurately positioned using the CNC, the fixing holes for a new part, such as a pump, can be drilled using the same position coordinates, even when several years pass between the two operations. There is rarely a need for oversize or oval holes. You will therefore understand how important it is to include ALL fixing holes at the CAD drawing stage and then to 'freeze' the drawing.

Mike

PS. I think the knight in shining armor could become known as "Sir Clip"

[crueby]

SirWarf (said fast, SirWarf, SiWarf, Swarf...)!   

[Vixen]

 Sir Warf           A chip off the old block

[crueby]

Sir Warf           A chip off the old block

[Zephyrin]

thanks for the answer Mike...
following a flawless design, "frozen" for years, is another world (planet?) to me!

[RReid]

My own frozen designs often seem to have a very low melting temperature... 

[Vixen]

High Pressure Fuel Pump

The next item on the seemingly endless list (I don't expect to be starting another of these epic engine builds, so I had better make this one last) is the high pressure fuel pump, driven off the left hand accessories shaft, outboard of the supercharger scavenge oil pump. The full size W165 engine pumped a toxic mix of methanol, nitro-benzine, acetone and ether into the supercharged engine at high pressure and high flow. The tiny 1.5 litre engine consumed fuel at about 3 or 4 miles per gallon, at full chat.

The fuel pump is a straight forward gear pump. There is an external pressure relief valve to control the fuel pressure delivered to the two carburetors.

I started with the adapter flange which attaches the fuel pump body to the scavenge oil pump. The adapter flange starts life as 30mm diameter aluminium bar stock. The first operation is in lathe, to turn the outside profile and bore the central hole for the bearing. You will notice, I used a 2mm radiused parting tool blade to make the profile cuts. These parting blades willingly cut sideways as well as make plunge cuts; provided the depth of cut is kept small. I machined these profiles using many passes each with the depth of cut increased by 10 thou. All that repetition only takes a few minutes with the CNC and the radiused corners are very pleasing to the eye.




After parting off, the four mounting holes in the scavenge pump flange were drilled to size.




The embryo adapter flange could now be bolted on to a sacrificial jig plate to enable the fuel pump flange to be machined. I picked off the centre of the bearing hole as my datum and machined the square outside profile and drilled and tapped the four mounting holes. The register hole for the second gear shaft was also completed, all at the same datum setting.






The fuel pump body and the outside cover plate were the next items. Both parts were straight forward profile milling operations. Both used same sacrificial jig plate, with four new mounting holes drilled and tapped to match the flange on the previously made adapter.






Here are the three part finished components sitting in line wondering what happens next.




The final (for now) operation on the fuel pump body was to drill and tap and round off the three input/ output bosses. The external pressure relief valve fits above the lone boss on the side. All connection to the fuel pump will be with banjo fittings.






There's more to follow, so stay tuned

Cheers   

Mike

[Roger B]

Off to a good start   

Are you intending to use it as a fuel feed pump?

[Admiral_dk]

Great to see progress again Mike 

I'm guessing that the parts needs a bit more fetling (sp?).

Rogers question makes sense - if you do use it - will it require an 'overflow system' ?

Per       

[Vixen]

Thank you Roger and Per,

You both make a good point about the use of that fuel pump on the model engine. The full size pump, which I am copying in 1/3 scale, was sized to provide more than enough fuel for 300 HP at 8,000 RPM. Even when scaled down, the model pump will still provide fuel well in excesses of my requirements. The output of a gear pump is proportional to speed, so some form of regulator is required to control (overflow) the excess fuel sent back to the tank.

I will be using diaphragm 'float chambers' which are best suited to gravity feed, as opposed to pumped feed. I expect to use a gravity tank on the model, for simplicity. Actually, I have a choice of two fuel feed options. The racing car did not have both options, it needs to pump the fuel from car's fuel tanks, situated in the tail and over the drivers lap.

Just for you Per, I did some more fetling on the pumps.       Here you can see one assembled (less the gears). Standard M2.5 nuts are big and do not look quite right, so I tried some of the commercially available under-size M2.5 miniature nuts (on the left). I did not like their look either. I resorted to drilling and tapping standard M2 nuts. You can see those of the right, to my eyes they look much more realistic.







This is the fuel pump mounted on the engine, outboard of the supercharger scavenge pump. Mercedes Benz may have produced some of the most powerful race engines, but the snake pit of external pipe work was a mess, almost as bad as the tangle of oil pipework in the dry sump.






Now that all the accessories on the left side are complete and in place, I now know what space they want to occupy and can now try to bend the external copper coolant pipe to fit correctly.

I was about to make a start on the banjo fittings and the pump gears. When I switched on the lathe yesterday, it went phut  and refused to start. I suspect it is the main PSU at fault. The PSU is over 40 years old, it's all discrete components, transformer, rectifiers and capacitors etc. so relatively easy to fault find and fix, assuming I can still buy the components.

One step forward and one step back. Patience !!!!

Cheers   

Mike

[Admiral_dk]

Woa - just as I thought - you had to bring the latest parts up to the same standard as the rest 

I'm usually not bothered much about Nuts as long as they do their job, don't corrode or look really bad .... But I do get why it matters when you try to achive an exact replica of the original - so yes the last pic has the best match 

Argh  - Yes that is annoying .... But you can usually still get Discrete Parts that will do the job just as well as the original ones today - though they might be in a 'Different Package' ....

I Hope the repair isn't expensive nor take long to fix ....

Per