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

[Kim]

Wow!  Just wow!

Are those parts JP welded together?  Or attached in some other way?

Kim

[Vixen]

Hello Kim,

Ideally, that part should have been a casting.  I have had no success with these aluminium solders you see being demonstrated at the shows. Unfortunately, I have had to resort to JB Weld.

Mike

[Kim]

Thanks Mike,
Yes, of course!  I have been reading those posts too.  Somehow, I didn't think about this being aluminum...  Sorry to make you explain it again.

Kim

[Vixen]

Hello Kim,

Your main interest is in steam locos; where the 'normal' materials are iron, steel, copper, brass and bronze. It's natural for you to think in terms of these materials, which are amenable to soft (lead) soldering, hard (silver) soldering and brazing, not to mention the various 'home shop' welding techniques. I wish the same were true for aluminium alloys.

Mike

[Brendon M]

MIG can weld aluminium, if you didn't already know

I will get back in my box
 

[Brendon M]

Nice!

I mentioned the MIG mostly because that's what most hobbyist workshops may already have*, whereas AC capable TIG machines on the other hand tend to be on the expensive side.

One thing I really want to try is building up rough shapes with welding which then get machined, kind of like casting

*unless like me their masochistic tendencies run deep and they have a buzzbox stick welder

OK I shall stop hijacking the discussion

[Vixen]

Coolant  Pump

Yes, I know it’s been a long while since I last posted an update on the Mercedes W165 engine build. The reason is simple, health issues have conspired to keep me out of the workshop for most of last year. None the less, I am still trying to make some slow progress, although the winter weather makes the unheated outdoor workshop is not very appealing.

I decided it was high time I did something about that wooden dummy water-pump which has adorned the right side of the engine for a few years. The water-pump is a nice self-contained unit that would serve as a suitable challenge to keep both my mind and fingers active





Below you can see a cross section through the front part of the M165 engine. The water pump is on the left and the supercharger scavenge pump drive is disappearing, out of sight, to the right. This blueprint is dated June 1939. If you can read the parts call out, you can see this water pump used many parts from the previous M25  and M154 designs. Obviously this saved design and manufacturing time.



The water-pump is a self-contained unit with a conventional centrifugal vane pump which is driven, via a pair of bevel gears, off the supercharger drive's intermediate gear, at about 2/3 engine speed. The centrifugal pump draws coolant from the radiator into the eye of the centrifugal pump. You may notice at the top, the involute's output port is divided into two. One half provides coolant for the left bank of cylinders and the other sends an equal quantity of coolant to the right cylinder bank.
 





Here you see the mounting flange for the water pump, angled downwards at 30 degrees. There is an identical mounting flange on the other side of the crankcase for the superchargers scavenge pump and fuel pump drive.

Just to the left of the water-pump mounting flange you can see a flanged hole passing through the magnesium alloy crankcase. This was intended to carry the water coolant across to the other side of the engine. This did not turn out to be a good decision by the Mercedes design office. The coolant was plain water with no additives, the cylinder blocks were welded steel, the water pump was cast aluminium and the coolant was pumped through the magnesium alloy crankcase. No consideration was given to the possibility of galvanic corrosion, which was inevitable considering the mixture of different metals. The net result was the hot coolant reacted with the magnesium ally crankcase. The walls of the coolant passage through crankcase casting eventually corroded away and the coolant leaked and mixed with the engine oil. The fix employed by the Mercedes design office, was to abandon the coolant through hole and make an external steel pipe connection to carry the coolant around the front of the engine to the opposite side of the engine. That external pipework is still there today, 80 years later.

Best to tune in again as there is more to follow.

Mike                                                     

[crueby]

Just got in another box of 'wow's, so I'll use one here.  Wow!   

[RReid]

Hi Mike. I always look forward to your updates on this engine, no matter how long between.

[cnr6400]

 

[steamer]

I'm suprised Mercedes  mixed all three alloys .     I suppose they didn't count on them to last 80 years

Watching along Mike and glad to see you in the shop.

Dave

[Vixen]

Coolant Pump 2

Thank you all for looking in and especially to those who called in. 

Dave, Getting back to the shop is a positive sign, even if it is only for two to three hours on a good day.

The first item made for the water pump was the main body, which incorporates the mounting flange and the inboard bearing. The first operation was some profile turning on the lathe. Followed by a visit to the mill to have the mounting flange profiled, the holes drilled and tapped.









The two side plates for the pump involute came next. These were machined entirely on the mill. One side plate carries the outboard bearing and the lip seal, the other plate is almost identical, except for the center part which connects to the water inlet elbow.








Stay tuned

Mike

[steamer]

Mike I know your have a blast cabinet   do you keep it outside the shop

Dave

[Vixen]

Hello Dave,

My blast cabinet is quite small but more than adequate for model engine parts. It measures about a metre (3 foot) cube. It's mounted on wheels so I can take it outside to use (when it's not raining!!). I would not want any stray wind blown abrasive or beads to find their way onto or into the machines. Last year I bought a big tub of fine aerospace grade glass beads which get used over and over again. The glass beads don't seem to brake down into dust like the abrasive grit.

As you can see from the photos above, the beads leave a pleasing pearl finish on the materiel.

Mike

[Laurentic]

Mike - good to hear you are fit and well enough to venture once more out to the shed - but surely you must have some sort of heating there, even if it is just a cheap electric fan heater?  I have that, not that I use it much these days, and a little oil filled radiator which I find works quite well indeed.  Takes just 1600W of juice max.  You need to keep warm out there!

Loved the latest work, you haven't lost your touch, but how was the pump main body held for the base profiling and hole drilling/tapping?  It looks like it was stuck to a piece of perspex held in the vice, what did you use to stick it if that were so, and how was it removed?

This whole engine continues to absolutely amaze me, with its attention to detail and complexity of design: Merc had loads of resources back in the day, you have just what's in your shed, what you accomplish is simply astonishing.

Chris.