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

[Michael S.]

Excellent job Mike!
An absolute highlight.
Does Mercedes-Benz actually know that you build such a model engine?
They will want a number 2 from you for their museum 😁

Michael

[Vixen]

Mike, Art:
I am pleased you enjoy the installments of my long journey. I enjoy each step as well, the making, the photos and the write-up on the forum.

Michael,

Ha ha. You could ask Mercedes Benz to contact me and make an offer. There are two model M165's to chose from.

I have a good relationship with the guys who run their historic car department, then try to be helpful as they are permitted, but are forbidden to hand over any technical details. The MB legal department make life difficult for anyone selling anything to do with MB which has not been manufactured or authorised by MB themselves. Famously, a few years back, they were able to confiscate two well made "Gull wing" sports car replicas and have them destroyed. Fortunately, for me, they can only do this on German soil.



Prost   

Mike

[Laurentic]

Done it again Mike - missed your latest by a day, but this time I had an excuse, yesterday I had a cataract op and was out the game for the day.  Not so in the game today either!!

However, as ever, full of admiration for your work and the detail you give and put into what you do, simply amazing and all on such a high level - excellent.

Cheers,
Chris

[Vixen]

Hello Chris,

The recovery from a cataract opp is usually quick and the effects immediate. Are you having the second eye done in about 6 weeks?
You get the full effect, when both eyes have been done and stabilised, and you buy a new pair of prescription glasses.   

Cheers   

Mike

[Laurentic]

Hi Mike - my eye is feeling better this evening thank goodness and far less tired than earlier today.  Will make a decision on the other eye (which was not as bad) in four weeks time when I see the optometrist again and get his view and will probably go for it.  Seeing quite an improvement already - which is encouraging! 

The optometrist said before he sent me for the op that there was absolutely no point in prescribing new lens for me unless I had the op done as nothing would improve what I have now, so it was a bit of a no-brainer really!   

Looking forward now to, as you say, the eyes stabilising and then getting a new pair of specs. 

Sorry if this has sidetracked your thread for a minute - hope it hasn't distracted from your excellent thread.

Cheers
Chris

[Roger B]

Excellent work as ever   

I don't remember if this was discussed before but you have a Walbro type carb fitted in the pictures. I thought that they required the pulsing from a single cylinder to operate properly?

[Vixen]

Excellent work as ever   

I don't remember if this was discussed before but you have a Walbro type carb fitted in the pictures. I thought that they required the pulsing from a single cylinder to operate properly?

Hello Roger,
I don't think the carburettors have ever been discussed on this forum. They did attract a lot of questions from Roland Asch, the Mercedes Benz test driver of the W165, at one of the Goodwood historic meetings.

The whole question of carburettors for this engine is an interesting one. There are a lot of unknowns, like how much air will the model superchargers actually draw and what fuel to use etc, etc.

Back in it's day, the full size W165 burned a over rich mixture of methanol, acetone and nitro-methane, blown into the engine at 2.6bar. The over rich mixture, evaporation cooled the supercharger and cylinders; the fuel cocktail they used was also almost a mono-propellant, therefor less dependent on the amount of air available. Not a very helpful starting point for a small model engine.

The Walbro style carburettors you see are very much a place marker, rather than the definitive answer. That will need a lot of experimentation to sort out. I have currently fitted a pair of 'walbro' style diaphragm carburettors, one has a larger bore than the other. I can attempt to run the engine on either the small bore, the large bore or both carburettors simultaneously, or change them so both have the same size bore.



Both of the 'walbro' style diaphragm carburettors are heavily modified to fit side by side at the front of the supercharger. I have machined away the mounting flanges and the whole of the diaphragm fuel pump leaving only the diaphragm 'float' chamber, fuel metering jets and the venturi. In theory the modified carburettors should now run from a gravity feed tank. I have not actually tested that yet. When it comes time to try and run the engines, I expect I will fit a big conventional float carburettor before playing with the more scale size modified walbros.

Cheers   

Mike

[Vixen]

Gee Mike, when you decide to slow down; you really do slow down.............. to a stop.

Not been feeling too good recently, one of my medications knocked the stuffing out of me for several months. No workshop time, I had to be content with being an armchair engineer. Thankfully that course of treatment is over, so I am venturing into the workshop again; just an hour or two each day. However, with a little planning I have been able to make some more slow progress on the Mercedes engine.

The first thing was to order some more material. A 1.5 metre length of 50mm x 19mm aluminium ally 6084 was ordered and delivered and cut into 8 pieces. Is it my imagination or has the price of aluminium stock skyrocketed?





Can you see what they are going to be yet? I will tell you tomorrow

Cheers   

Mike

[RReid]

Hello Mike,

Great to hear that your stuffing is getting shoved back into place and you are starting to feel better. Not sure what you have in mind for those bars, but I'm sure it will be good!

[Admiral_dk]

Great new that you are feeling better Mike    even a few hours are better than none 

One of the few thing where the prices haven't skyrocket is gasoline / petrol (or what it is called @ the different readers location) since Covid    and that is probably down to how many cars that are electric nowadays (not so much sale)....

Looking forward to see what you are up to now 

Per         

[Laurentic]

Good to hear that you are feeling better Mike, but I can appreciate where you are coming from. 

Whilst I am not at all in your league of disabilitating inflections, my cataract op is still not resolved completely - still have some inflammation behind the eye despite the standard 4 weeks of eye drops, then plus 12 weeks on eye drops, with today another 4 weeks of drops added to go, plus the long-covid type symptoms being so slow to subside, coupled with lately some family duties, meaning my shed time severely curtailed too.  I shall be trunderling along the M27 on Wednesday to West Sussex and back again Friday for another family medical duty, so if you hear a shout of "do you fancy a beer MIke" that'll be me!  So I can so keenly appreciate how your lack of shed time has been diminished.  Too much and many cancellations "due to acute lack of interest" on the day!!

And yes you are not mistaken, prices of aluminium and metals generally have gone up hugely thses past few months, eye wateringly so it seems.  At one time, a few months ago now,  I queried this with M-Machine Metals and was told that prices (at that time) were going up by the day.  Our (UK) energy prices and current state of the metals industry is certainly not helping any!!

And no, I cannot guess what those bars of ally will be!!!!!!  But am watching with bated breath to discover what!

Chris

[Charles Lamont]

Cam covers?

[Vixen]

  Part 34  Cam Box Covers

Hello Ron, Per, Chris thanks for calling in. I was not sure anyone would be still following this long winded build, after a four month break.

And the prize goes to Charles. You are correct, the aluminium blocks are intended to make eight cam box covers, four for each of the two engines. However most of the  3.5 Kg of aluminium will be converted to a huge pile of chips along the way.

The manufacture of the Cam Box Covers could conveniently be broken down into two major activities. The first activity (CAM phase) was to produce the large number of tool path programs ready for the subsequent CNC machining phase. The tool path generation could be conveniently carried out in the office at a pace which matched my energy levels. The machining phase was reasonably straightforward, mostly machine minding (watching) while the CNC mill did the work of creating the part. As you can imagine, with eight pieces, the machining phase became very repetitive and time consuming. I was able to set a pace which matched my energy levels. If I did too much one day, I paid the price by having to skip the next day in the workshop.

Although the cam box covers all look the same, Mercedes Benz conspired to make things difficult for themselves (and me) by making the four cam box covers on each engine to slightly different designs.  One pair of cam box covers is longer than the other due to the stagger of the two banks of cylinders. Add to that, one cover of each pair is mirror image of it's companion. So I needed to make two copies of four different cam box cover designs. This was going to call for a systemic approach, good planning, a well thought out tool path identities (names) and carefully marking each part as work progressed. The last thing I wanted was box full of left hand boots.

I only have 2D CAD and 2.5D CAM available with which to produce the required complex 3D shape of the cam box covers. My process was to create a series of contours (like the height contours on a map) by old school drafting methods. The individual contours were converted into tool paths by my CAM software and added together to make large CNC program: inside shape, outside shape, base flange shape etc. The contour map needed to consider the exact contact point were the cutter would contact the cam box cover. I chose to do all the machining with a 6mm diameter 2mm radius bull nose cutter. That's a Bull nose not Ball nose cutter.

Below, you can see an example of the height contour map used to produce one of the inside and outside 3D shapes. The contour maps also need to be mirror imaged and have the overall length changed to match the four different cam box covers variants. The machined part will always consist of a series of narrow cut facets, which need subsequent hand finishing to achieve a smooth polished surface. The fineness of the facets is always going to be a trade off, more finer facets mean less hand finishing but considerably more tool path programming to achieve. It's a compromise; I chose 27 equi-spaced facets for the outside surface and 20 equi-spaced facets on the inside. Also shown on that drawing is the outline shape of the stock and the fixture holes to locate the stock during machining.




Outside in the workshop, each piece of stock was mounted in the machine vice supported on a stack of parallels on both sides. The fist opp was to coordinate drill the fixture location holes at the outer corners. Then the base flange outside profile was machined and all the cover attachment holes drilled. This was followed by machining the inside 3D shape with the 6 dia 2R  corner radius bull mill cutter. The chip clearance capability of a bull nose cutter is limited so feed rates need to be reduced accordingly. In hindsight It may have been quicker to have created an additional roughing stage using a two flute end mill to quickly clear the majority of the material from inside the pocket.








Below, you can see the inside 3D surface of one of the cam box covers. The number of facets can be seen. I used my peristaltic coolant pump, delivering a miserly 9 drops a minute (that's only 6.6ml per hour) of Sorotec S3G synthetic coolant and an air blast to lubricate the cutting edge and clear the chips from the working face. The inside face took about 1 hour of machine time, so I could achieve maybe two parts to this stage, in my reduced working???? day.




The process was repeated eight times over, with due allowance for the mirror imaged and different lengths of the cam box covers. The chip pile at the left side of the milling machine cabinet is starting to grow.




Finally, a family shot of the eight embryo cam box covers all carefully marked to ensure there were two examples of each of the four variations.




Hopefully, I will be able to add another installment from Vixen's den tomorrow.


Stay tuned

Mike 

[Dave Otto]

Nice work Mike!
Good to see progress.

Dave

[steamer]

Those look fantastic Mike!!    Im glad you're back on it!

Following along!

Dave