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Author Topic: PhilTech 1.5 D con rod  (Read 655 times)
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Fourfingers
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« on: February 17, 2018, 12:47:24 PM »

OK you guys down under ....
Just got a nice black (limited edition?) PhilTech.  A strange  - to me - occurence, in that if the engine is flipped with the backplate removed, the con rod comes away free from the crankpin.  Mever seen that before.  Quite difficult to fix, too.
OK, I hear you say: why do that?  Lets not go there!
One side of the big end hole on the rod is bevelled or chamfered, if that is understandable.  I'm wondering if that is the side to go nearest the crank web?
Nice engine though.  Anyone know if they are still made?
Relying on you Oz/NZ cousins.
ff
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ffkiwi
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« Reply #1 on: February 17, 2018, 03:36:14 PM »

The bevel should go on the crankpin side-this is because-except in the case of a pressed-in crankpin-(used by a number of manufacturers) there will always be a slight radius where the crankpin emerges from the crankweb, and the slight bevel or countersink on the conrod big end is to accommodate this radius, otherwise the rod would not seat properly and friction would be considerably higher. This radius in an inevitable result of machining the crankshaft-you can't have a lathe tool with an infinitely small point-even on a corner tool, such as would be used for the finishing-and then the pin is (hopefully) ground-and the same point applies-grindstones don't have sharp 90 degree edges at the microscopic level
      It is always wise to check on second hand engines as there are an amazing number where you find the rod in the wrong way-invariably done by past owners, and not the factory.....

 ChrisM
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Fourfingers
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« Reply #2 on: February 18, 2018, 05:37:48 AM »

Chris, thank you again for this. 
The intricacies of engine manufacture escape me - I never progressed beyond hammer and chisel - but your explanation chimes with Duncans article on the PhilTech.  Unorthodox but practical methods, in some cases.
Got the head off, its a full jacket rather than the 'top hat' shown in the article.
Reveals a liner retained with a circlip which felt very well attached .... not sure how to get that off.
Would be handy to check wrist pin and little end .... feels kind of free to me.
Perhaps a soak for a few days then have a go?
Thanks again
john ff.
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Fourfingers
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« Reply #3 on: February 19, 2018, 07:28:53 AM »

The plot thickens .....
Got the liner out - lots of oil, a little heat, some intimidation.  Piston fit v good, as is main bearing. But .... little end seems very wobbly. Play every which way except in vertical direction, the way it operates!  Also - and I know this cannot be - the visible ends of the wrist pin look like plastic!
Seems hard to reconcile great fits all round except wrist pin/con rod connection.
Any help here from you PhilTech experts most welcome, thanks.
Jc aka ff
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ffkiwi
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« Reply #4 on: February 19, 2018, 02:54:04 PM »

Well you can rest assured that the gudgeon pin isn't plastic-I doubt that any plastic exists that would have sufficient shear strength in the dimensions of the Philtech pin. And the loading on pins IS shear/bending load-which is why they do snap from time to time! The ENDS may well be plastic-these are known as 'endpads' [surprise surprise!] and their sole function is to prevent scoring or the bore by the gudgeon pin should it work sideways in use and come in contact with the cylinder walls-given that gudgeons are usually fairly hard!   Endpads are made from a variety of materials-brass, PTFE and may be mushroom or eyelet style depending totally on the manufacturers whims. Some manufacturers make the pin a press fit, others locate it with wire 'e' circlips, others use a slight taper at one end and different hole sizes-in all these cases you don't find endpads-in the cases where the pin is fully floating-it is normal (in modern motors) to use end pads-but not necessarily universal practice. You will find plenty of 50s and 60s diesels with fully floating gudgeon pins-and just domed or rounded ends to the pin.

 I cannot comment much on the little end wear specifically-other than to say that diesels can be quite hard on rods-even paragons like the Mills 75 used to chew through rods during a lifetime (it was the only part that did wear, if you used them sensibly!)-and DC Merlins could be absolute shockers for wearing rods out. One thing you could try-just for interest-is fitting a prop with the cylinder and head removed-and seeing how much clearance there is between the backplate and the crankshaft-spin the prop in the normal direction and see if the rod moves back on the crankpin. Whilst this won't duplicate what happens in running-it might indicate a tendency for the rod to work back-and hence adopt a non perpendicular attitude while running-and this will certainly contribute to excessive rod wear.  This is always a challenge for the manufacturer-some clearance is needed as you dont want the crankpin and rod rubbing on the backplate-for obvious reasons-but too much fore and aft has the effect already mentioned. Very few engines have the rod movement restricted-there are a few-some K&Bs, the Frog 500-some of the better glows-since it just adds cost-a few of the more enlightened manufacturers did-Cox with the Special 15, using spacers on the little end-and Barbini IIRC. There is a negative to this as well-in use, there is always the risk of fuel residue-and heat-locking the spacers rod and gudgeon together-so that instead of the rod rotating on the pin, during running, the entire assembly rotates in the piston bosses-and slogs out the gudgeon pin holes with time.  I've had this happen with a K&B GH 19

 ChrisM
 'ffkiwi'

PS..a final thought-since it appears the engine is not new-a previous owner may have hydrauliced it whilst starting-in severe cases this breaks/bends the crankpin and/or gudgeon-in minor cases it may bend the rod-in which case you can confidently expect accelerated rod wear-even if no other symptoms are obvious.....
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Fourfingers
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« Reply #5 on: February 20, 2018, 04:34:57 AM »

Thanks Chris
So much knowledge on these forums, great stuff.
We have a very good engine doctor here, a job for life perhaps with idiots like me around.
I think this is another one for him!
john
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