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

[petertha]

Beautiful work. I ran into similar questions but have not had the time to delve further as you have. What is the 'one drive' you referenced?


I tried several different formula from a number of sources to define the required button diameter and centre distance. The different sources all produced slightly different diameters and offsets. I laid out each of the cutter solutions and gear pairs on a CAD drawing to make a comparison. I eventually selected the button dimensions suggested by 'One drive'.

[Admiral_dk]

Nice progress none the less Mike 

Per       

[Vixen]

Hello Per and petertha,

Thanks for calling in.

Peter, If you Google " gear cutters, button method" or other variations on the same theme; you will discover several different websites all claiming the 'correct' method for calculating the button size. Included in the list was Ivan Laws work on gears and gear cutting, usually taken to be the bible by model engineers. None of the sources agreed with the size or separation distance for low tooth count 10T gears. So, which one was correct, which one should I chose? I was out there all on my own.

In desperation, I drew up each of the proposed cutter solutions on a CAD drawing and compared the results. Again, none seemed to be correct, usually the teeth were seen to clash and try to overlap. When I opened the centre distance from 7.0mm to 7.2mm one of the proposed solutions looked better than the others. That one had 'One drive' in it's title. There is no logic which says it was any better or more accurate than any of the others. So basically, I just fiddled with the CAD dimensions until I found something I felt happy with and went from there. An optimised design, or an engineering compromise, or just luck... you decide

Whichever, as you can see, my hunch worked.

Mike

[steamer]

I had similar challenges on my pump.     Interesting relief valve there....any pics?

Dave

[Vixen]

Hello Dave,

Good to hear from you. The PRV is only a dummy, the pics you see are all there is. We would be kidding ourselves if we thought a valve that small would be capable of doing anything useful or reliably. If I do use the fuel pumps, the fuel will circulate back to tank through a small restriction. The carbs can grab whatever they need from the return flow.

Cheers   

Mike

[Laurentic]

Lovely work there Mike, love those oil pumps. 

I don't know why it is, i check this site frequently to ensure I try and keep abreast of interesting (to me) threads, and everytime I seem to miss yours by a day. So frustrating!

Where did you get that 2mm radiused parting tool insert from?  I have been looking at all the usual sources I haven't seen one.  Thought it was such a nice little useful tool to have.   

Chris

[Vixen]

Thank you Chris.   

I find I am using these 2mm parting blade more and more for fine turning and profiling, as well as for parting off. They cut sideways nicely, provided you you keep the DOC small.  I find my inserts on e-bay.

2mm square end parting inserts                                  MGMN 200
2mm square end polished inserts for soft materials    MGGN 200
2mm round end (R 1mm) inserts                                  MRMN 200


Cheers   

Mike

[Laurentic]

Thanks Mike - looked on EBay (hadn't checked that one out) and there are loads there.  Sorted!

Chris 

[Vixen]

Part 33   Pumps and External Pipework

I have made a little more progress with the external pump installation and pipework at the front of the engine.

I made up the oil scavenge pump driveshaft and fitted the bevel gear. The forked extension of the drive shaft turns the fuel pump.






I then turned my attention to the external coolant pipe feed from the coolant pump to the cylinder water jacket.

You will recall, the original design of 1939, pumped the coolant through the aluminium crankcase from the pump to the left hand cylinder water jacket. When Mercedes Benz rebuilt the two cars at the Fellback works, sometime in the 1950's, they discovered the coolant had badly corroded and eaten away the walls of the passageway through the engine block during the intervening years. The coolant was now leaking through the engine block casting and into the oil and dry sump. MB devised an external pipe to connect the coolant pump the the left hand cylinder block and abandoned the coolant through hole. You can still see the original coolant passage through hole in the next photo.

I made the external coolant pipe out of 8mm copper elbows and bends. I had tried unsuccessfully to bend some copper pipe to fit. After several failed attempts they were all consigned to the waste bin and I resorted to commercial fittings. The coolant pipes are connected to the cylinder blocks with the same style of half clamp as used elsewhere on the engine.







Here you can see the supercharger oil scavenge pump and the fuel pump installed. The external coolant pipe and the main oil return pipe to the external oil filter are all present. It's a mighty tight fit to get all that external pipe and tube into that confined space. It's a right mess to be honest, but remember this was 'state of the art' race engine design in the last 1930's. Today, everything would be fully integrated, in the interests of improving reliability.




For completeness, here you can see the coolant pump installation of the opposite side of the engine.




Here you can see the two drive bevel gears nestling in those two strange looking bumps on the front of the engine block. As with everything on this engine, there is little spare space inside that gear case.






Finally, another look back at the cross section through the front of the engine.




Cheers   

Mike

[Kim]

I apologize in advance for being so redundant, but I just have to say it again...

Wow!  This is amazing Mike!  The workmanship is incredible and the detail you include is amazing! 

Thank you for sharing this with us.
Kim

[Admiral_dk]

Can't say that you aren't persistant in your drive to get it right Mike 

And just like Kim - I haven't got more in my vocabulary that hasn't been used to describe the brilliance off this build.

Per         

[RReid]

Ditto all of the above. I always look forward to updates of this build, Mike. The work you do and the way you do it is always an inspiration, as well as a source of ideas.

[Vixen]

Thanks for calling in guys, your words of encouragement are always appreciated.

This engine is a very long, very slow journey. I'll get there one day.   

Mike

[Mike R]

Mike,

This made my day - another installment of your wonderful build.  Thanks for sharing with us.

Mike

[Art K]

Mike,
What you have done kind of boggles the mind, quite amazing. Look forward to each installment.
Art