Author Topic: Mercedes-Benz W165 Grand Prix engine in 1:3 scale  (Read 151570 times)

Offline john mills

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #555 on: September 26, 2021, 09:35:30 AM »
its fascinating to see these parts take shape i would wonder if they positioned the spindles then they could adjust the size of the gears if the clearance was not right but they probably got the sizes right.
john

Offline Vixen

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #556 on: September 26, 2021, 03:54:32 PM »
Hello John,

The cam shafts sit on top of a fabricated steel cylinder block, so the exact positions of the cam centres could also be variable, which adds to the need for backlash adjustment



MB recieved huge subsidies from their Government and added their own money from profits from the re-armement program. They were not short of money, facilities or workers. Each engine was hand crafted, I believe each gear would have been individually 'made to measure', each with a slight diameter variation. They could have fitted test discs of different diameters, to determin the exact PCD required for each gear, to minimise backlash.

It's all a guess, the guys who know, are no longer with us.

Mike
« Last Edit: September 27, 2021, 10:39:18 PM by Vixen »
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Offline Roger B

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #557 on: September 26, 2021, 04:47:26 PM »
Splendid machining as ever  :praise2:  :praise2:  :wine1:

The original fabricated cylinder block looks to have been a challenge   ::)  :thinking:  :headscratch:
Best regards

Roger

Offline RReid

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #558 on: September 27, 2021, 04:36:58 PM »
I was wondering if something like an eccentric spindle, turning inside a rotatable eccentric sleeve, could be used to adjust the lash in both x and y directions. Complicated, yes, and tricky to adjust, but as you've said, those things would be irrelevant to those guys!
Regards,
Ron

Offline Vixen

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #559 on: September 27, 2021, 05:38:42 PM »
Hello Ron,

Here is the only cross section I have of the full size gear train .



You can see the hollow idler gear spindle in the centre and again at the lower centre of the image. The spindle passes through the gear case and is secured, at the rear face, by four small screws. It's position appeares to be fixed. I can see no means of positional adjustment.

An eccentric spindle would work OK to adjust the backlash between two gears. However, in the W165 gear train, each idler is in contact with more than one other gear, so an eccentric sleeve would not have worked. I believe a 'made to measure' gear was the way that MB did it. I chose to mount the model's idler gears on adjustable bridges, but I am still trying to create the same extrenal appearance as the original.

Mike
« Last Edit: September 27, 2021, 10:41:10 PM by Vixen »
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Offline RReid

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #560 on: September 27, 2021, 08:39:15 PM »
Thank you for your reply, Mike, and the drawing image. It just gives me that much more respect for what you are accomplishing.

Quote
An excentric spindle would work OK to adjust the backlash between two gears. However, in the W165 gear trian, each idler is in contact with more than one other gear, so an excentric sleeve would not have worked.
I agree with that. I'm afraid I didn't describe my idea very well. The eccentric spindle would rotate within a sleeve with an eccentric bore. That sleeve would also be free to rotate within its gear case bore. If I'm correct that would seem, in principle anyway, to allow the idler gear lash to be adjusted for both driven gears by adjusting the two eccentric axes independently. Of course, means to lock both the sleeve and the spindle would have to be provided, plus means to rotate each with some precision.

I don't question for a second that your idea of how MB accomplished the job is the correct one, I was just imagining/day-dreaming a possible alternate way. :cheers:
Regards,
Ron

Offline Vixen

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #561 on: September 27, 2021, 10:30:11 PM »
Thank you for your reply, Mike, and the drawing image. It just gives me that much more respect for what you are accomplishing.

Quote
An excentric spindle would work OK to adjust the backlash between two gears. However, in the W165 gear trian, each idler is in contact with more than one other gear, so an excentric sleeve would not have worked.
I agree with that. I'm afraid I didn't describe my idea very well. The eccentric spindle would rotate within a sleeve with an eccentric bore. That sleeve would also be free to rotate within its gear case bore. If I'm correct that would seem, in principle anyway, to allow the idler gear lash to be adjusted for both driven gears by adjusting the two eccentric axes independently. Of course, means to lock both the sleeve and the spindle would have to be provided, plus means to rotate each with some precision.

I don't question for a second that your idea of how MB accomplished the job is the correct one, I was just imagining/day-dreaming a possible alternate way. :cheers:

Hello Ron,

Maybe that's yet another way to adjust the backlash. Good thinking/ day-dreaming :ThumbsUp:

Engineering is all about investigating many alternative solutions to a given problem. Then evaluating them all against your requirements, your facilities and your resources. Then weighing them all up, before you decide. Mercedes Benz did it their way, which worked. I chose to do it slightly differntly. Time will tell if it works as well as the MB solution.

Now let's get back to making chips.  :thinking:

Mike
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Offline Johnmcc69

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #562 on: September 28, 2021, 12:59:21 AM »
 Mike, did you try setting up the gear train on a "sacrificial plate" to work out the gear centerlines? & machining the bores "theoretically" where they should be?

 I would have to think that even mass produced gears would have some "level" of accuracy & could be easily changed out.(?) In full scale...
 What kind of accuracy is required for your model? I understand the timing requirements, but chain drive cam timing has to have a lot more "slop" & proved itself in production scenarios (not comparing to model making..).

 Not criticizing your design, I'm just trying to keep up following along.
 John

Offline RReid

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #563 on: September 28, 2021, 01:26:54 AM »
Quote
Now let's get back to making chips. 
By all means. You make chips, and I'll switch from popcorn to chips and salsa!
Regards,
Ron

Offline steamer

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #564 on: September 28, 2021, 02:28:59 AM »
GO MIKE GO!!!!!!


Its getting there my friend... watching and learning.....

Dave
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Damned ijjit!

Offline Vixen

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #565 on: September 28, 2021, 10:46:52 AM »
Mike, did you try setting up the gear train on a "sacrificial plate" to work out the gear centerlines? & machining the bores "theoretically" where they should be?

 I would have to think that even mass produced gears would have some "level" of accuracy & could be easily changed out.(?) In full scale...
 What kind of accuracy is required for your model? I understand the timing requirements, but chain drive cam timing has to have a lot more "slop" & proved itself in production scenarios (not comparing to model making..).

 Not criticizing your design, I'm just trying to keep up following along.
 John

Hello John,

Thanks for joining the discussion.

I am attempting to build a replica of a 1930's era racing engine, warts and all, with minimal design change. I do not wish to 'improve' or modernise the design. If I did that, the engine could easily become more like the W12 engine used today by Lewis Hamilton. Both the W165 and the W12 are/ were 1.5 litre engines with forced induction, but there the comparisons end.

In answer to your questions.  I have layed out the theroretical gear train centres using CAD, working to a higher precision undreampt of back in the 1930's. I also built a layout model (sacrificila plate?) in perspex using discs of the correct PCD.   From these I learned thee things

1 The camshaft gear drive unit is much larger than the movement available on my bench top mill. The work would need to be moved around on the table, multiple setups etc.

2 The camshafts do not end up in the theoretic position, due to an accumulation of manufacturing tolerances in the crankcase, cylinder block, cylinder heads and cam boxes. Close, but not precise.

3 There are 6 individual gears involved driving the left bank exhaust camshaft. If each gear had, say, 1 degree of backlash, then the left hand exhaust cam could have up to 5 degrees of backlash error. I need to be at least an order of magnitude better than that. So the need for some form of backlash adjustment became obvious.

My idea of mass producion gears was making 7 of the idler gears, from these I was able to select the best fit. I am sure that if today's precision toothed timing belt drives had been available back in the 1930's then Mercedes Benz would have considered using them. The advantages of modern precision timing belts speak for themselves.

Now I am off to the workshop to make some chips.  :thinking:

Mike
« Last Edit: September 28, 2021, 03:01:50 PM by Vixen »
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Offline Johnmcc69

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #566 on: September 28, 2021, 02:36:19 PM »
 :ThumbsUp:
 Thanks for the reply Mike! That certainly makes perfect sense now. (Especially not having the machine travel)

 Looking forward to more!

 John

Offline Vixen

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #567 on: September 28, 2021, 06:02:44 PM »
Meanwhile, back at the chip factory inside Vixen's den, things have been happening.

I am now more than half way through set-up #5 of six. As you can see the pile of chips in the cabinet is getting deeper everyday. By the time I have finished I will have reduced those two 10 mm plates to an average shell thickness of 1.5 to 2.0 mm. So far, so good; I havent broken through anywhere yet. There was a small miss cut on the top edge. I spotted it quickly and amended the toolpath program to avoid it happening next time



The good news is:  I still have the datum corner and a datum face intact ready for the 6th and final set-up.

The bad news is: I now have to hand program a set of contour lines required to create a 5.5 mm radius on the outside of the gear cover plate in order to finish set-up #5.

It's getting tence, I would not like to have to start over again.

Mike
« Last Edit: September 28, 2021, 06:33:51 PM by Vixen »
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Offline Roger B

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #568 on: September 28, 2021, 08:10:01 PM »
Looking good  :praise2: The question, as always, is how good does it have to be for a model display engine? I know I don't have much tolerance with my fuel injection systems but for a valve train drive system as long as the gears engage and don't jam how precise do you need to be???  :thinking:  :thinking:  :wine1:
Best regards

Roger

Offline Vixen

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Re: Mercedes-Benz W165 Grand Prix engine in 1:3 scale
« Reply #569 on: September 28, 2021, 11:21:19 PM »
Looking good  :praise2: The question, as always, is how good does it have to be for a model display engine? I know I don't have much tolerance with my fuel injection systems but for a valve train drive system as long as the gears engage and don't jam how precise do you need to be???  :thinking:  :thinking:  :wine1:

Thank you, Roger,

"The question, as always" sounds like you have asked this question before.  If so, I am sorry as I cannot recall it.  :embarassed:

" how good does it have to be for a model display engine?". For any engine to run, whether model or full size, single or multi cylinder, display or working; the compresion, ignition, carburtion and valve events must be within certain limits. Fortunately, for all of use, there is a certain amount of leeway. You can be several degrees out and the engine will probably run. I am hoping to get the backlash in the most distant camshafts down to within a degree or two, or at least as low as possible. I certainly wont accept a sloppy fit.  :hellno:

Your injection systems do not have the same leeway. The requirements for you fuel injection systems are far more demanding, requiring tighter fits and tolerances etc, an order of magnitude tighter than the average model engine. You are obviously enjoying that challenge.   :praise2: :ThumbsUp: :ThumbsUp:

Mike
« Last Edit: September 28, 2021, 11:26:39 PM by Vixen »
It is the journey that matters, not the destination

Sometimes, it can be a long and winding road

 

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