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

[Admiral_dk]

I really like your sequence Mike  - my thoughts where more complicated 

How much clearance did you end up with, between the Spigot and the Pilot Hole ?

Per             

[Vixen]

Hello Kim and Per,

Thanks for calling in and providing moral support.

Kim. if it were easy, what would be the challenge? 

Per, if I understand your question correctly; the spigot on each crank web is a light interference fit with the pilot hole in the faceplate. I hope that will keep everything concentric and square. 

Here is the crankcase with all the oil pumps and pipework removed ready for the action.

I did a trial fit with some of the crank shaft parts inside the crankcase. It's a tight fit, it's meant to be that way. Interestingly, I could only fit the crank web discs in three of the bays, the oil pipe lump on the side the crankcase 'casting' in the front bay, does not give enough clearance for a complete disc. However it will fit comfortable when the rear of each of the crank webs is machined away to form the counterweight.







Stay tuned

Mike

[steamer]

Working a lot of hours Mike but following along    stick with the larvae crank will bloom!

[Vixen]

Hello Dave,

Thanks for calling in. Sounds like they are keeping you busy.

Larvae?? Whats that about larvae? The last larvae turned into this thing, tying to get in through the office window to eat me. 




It's actually quite beautiful.
Can anyone identify it?

Cheers

Mike

[Bluechip]

Not usually the elevation to identify moths, but ...

Garden Tiger Moth ??

https://ukmoths.org.uk/species/arctia-caja/

Dave

[Roger B]

I am following the crankshaft along and like you am interested in how square and parallel you can keep it all     

[Vixen]

Hello Dave and Roger,

Roger, Keeping everything square and parallel is absolutely essential. I will do the best I can and hope for a successful outcome. I am sure the Schilling method of achieving alignment from the roller bearing inners is more likely to work in a hobby environment, than trying to attempt nine or more of these Hirth couplings.




Dave, Looking at your link, you may be right about it being a Garden Tiger Moth. I was rather expecting a biplane with a propeller up front.

Cheers

Mike

[Vixen]

It's been a busy day in Vixen's den. Lots done today.   

The next opp is to turn the rear face of the crank webs and to turn the offset big-end journal. To do that, I first need to accurately move the fixture plate by half the stroke distance; so a setting tool was required.

Some aluminium round was turned to the same size as the main bearings and a concentric ground steel rod fitted. This was then mounted on the milling machine in a three jaw chuck (my preferred method of holding round stock on the mill). The mill was clocked in and zeroed, central to the steel rod. The mill was then off set by the required distance and a second hole was drilled and reamed to accept a second ground steel pin.





The setting tool was transferred to the face plate fixture, I used to turn all the main bearing journals. The position of the faceplate was then adjusted in the four jaw chuck and clocked in to be concentric with the offset pin in the setting tool.





The re-positioned faceplate fixture was again faced off, to ensure the working surface remained square and true to the lathe's axis





The first crank web was bolted to the face plate fixture with a socket head screw through the big end journal, as in the previous opps. The rear face and the big-end bearing journal could then be turned to size. Note, the counter bore for the main bearing fixing bolt head slightly eclipses part of the big-end journal.







Here is the first crank web disc after the third opp. I have marked the approximate shape of the counterweight on the disc. A con-rod and big-end roller and it's roller bearing were added to confirm everything fits. I am using sealed bearings during the manufacturing stage, these will be replaced with open style bearings later, when there is less swarf around.







Machining the rear face and big-end journal is slow and time consuming because of the eccentricity and need for accuracy. The good news is: one has been completed,    the bad news is there are 15 more still to do. 

That may take a while, so Tune in later

Mike

[Jasonb]

Mike could the mill be put to use to do the majority of this operation and then just do the final facing and finishing of the spigot on the lathe, should be able to set one going on the mill while you turn another.

I'll go back to quietly following along now

[Vixen]

Hello Jason,

Thank you.  Yes, I thought about that. The mill would certainly remove metal at a faster rate. However, it would require another fixture plate for the mill with the added complication of devising some way of re-locating the parts at the correct rotational orientation, as they move from one machine to the other. Most, if not all, of the lathe work would been to be repeated; mostly cutting air. The current method is slow and tedious but has the virtue of being a simpler, single action, set-up. I'm in no big rush; I'm not going anywhere.

Are you thinking of going to the Midland Show?

Cheers

Mike

[Jasonb]

Would have thought if you left a reasonable amount of diameter on the spigot you could position it by eye, say 2-3mm all round. A matching dia bit of something held in the lathe tailstock could even be used and brought up to the work which would just need rotating on the fixtures peg in the lathe and then locking into place. Your 3-jaw on the mill would do to hold it for the roughing cuts.

Not sure yet about the show, probably decide a day or two before. There is not really much I need so would only pick up a few odd bits of metal to save postage costs and then a quick look around the stands and exhibits.

[Hugh Currin]

Mike:

Thanks for the explanation for machining the disks. And then a demonstration of the process. Nice.

When I asked I thought you'd already squared them, just getting ahead in time.

Great work. Thanks.

[Roger B]

Are you using a centre drill to support the end of the reamer in the first picture?

[Vixen]

Oops sorry. Guilty as charged.

I admit to being too lazy to fire up the small lathe to make a dead centre for the collet chuck. Besides, the reamer is turning in the non cutting direction of the centre drill. It is only centralising the reamer, not applying any pressure.
I should have known that some eagle eyed person would notice. 

Cheers

Mike

[Vixen]

Other priorities and the hot weather have kept me out of the workshop for a few weeks and the hot weather has not helped. It's cooled off, so I am back in the shed making swarf, lots of hot swarf



Can you see what it is yet?

Some of that metal is coming off really hot and flying everywhere; you need long sleeves, otherwise it stings.

Cheers

Mike