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Author Topic: external oil filter  (Read 3337 times)

mike704

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external oil filter
« on: June 10, 2008, 11:19:51 PM »
I am considering a cross-country trip this fall and was considering adding an external oil filter, an oil cooler and an oil tank for extra capacity and cooling. has anyone else made these mods? any advice?
thanks
mike
« Last Edit: June 11, 2008, 01:37:12 AM by mike704 »
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geoffbaker

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Re: external oil filter
« Reply #1 on: June 12, 2008, 02:32:17 PM »
Do a search on "cooler" or "oil cooler" on this forum. I remember someone had a pic of a setup where they had tapped into the oil feed to the head.

Peter

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cyrusb

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Re: external oil filter
« Reply #3 on: June 13, 2008, 12:59:45 AM »
It looks a little ungainly, but it cant be bad. It certainly can benefit from the extra capacity and cooling.

oldsalt

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Re: external oil filter
« Reply #4 on: June 13, 2008, 04:48:09 AM »
I have some reservations about how much is gained by putting an oil filter in the oil line that supplies the rocker boxes.

Re. Filtering:  Seems to me that there is not much volume going up there.  It would have to be under some really high pressure for that tiny line to carry enough to make it worth while to filter.  Plus, again just my opinion, the stock oil filter is a good one.  Just because it doesn't look like the one that comes on a Chevrolet or a Harley doesn't mean a thing.

Regarding the hope that there will be some additional useful cooling:   The major obsticle to getting useful additional oil cooling useing a "tank" is that the hottest oil is the oil entering the tank [or filter housing].  Being the hottest it is also the thinnest.  There is always a stream of hot oil that goes straight to the outlet.  Even fins on the outside of the tank are of little help because the problem is caused by a thick layer of cooler, thicker oil is insulating the skin of the tank.  If it is not possible to tap into the main supply from the "return" side of the oil pump, and an proper oil cooler [not just another tank to get additional volume] is put in line there will not be a useful gain.  The drysump systems used on motorcycles should not be altered unless a person likes to experiment and is willing to accept unplanned consequences.  Possibly serious consequences.   
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Peter

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Re: external oil filter
« Reply #5 on: June 13, 2008, 12:00:10 PM »
I have some reservations about how much is gained by putting an oil filter in the oil line that supplies the rocker boxes.

A filter spliced into the return line (= rocker feed line) will filter all circulating oil.

Peter

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Re: external oil filter
« Reply #6 on: June 13, 2008, 01:39:28 PM »
I have some reservations about how much is gained by putting an oil filter in the oil line that supplies the rocker boxes.
A filter spliced into the return line (= rocker feed line) will filter all circulating oil.
Peter

The return pump is the larger of the 2 pumps. If one was to put an external oil filter that would be the best (and easiest) place to put it. The only thing is after a filter change the top end would be dry until the filter filled up unless a provision was made to fill it with oil before starting the motor.
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Peter

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Re: external oil filter
« Reply #7 on: June 13, 2008, 04:50:18 PM »
... Plus, again just my opinion, the stock oil filter is a good one.  Just because it doesn't look like the one that comes on a Chevrolet or a Harley doesn't mean a thing.

Opinions aside, the stock oil filter is some kind of gauze and, on a good day, acts as a screen to keep larger shavings out of the big end.
The stock iron engine does not effectively filter its oil.

Peter

geoffbaker

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Re: external oil filter
« Reply #8 on: June 13, 2008, 07:00:16 PM »
I'm probably going to add an oil cooler to my diesel. But that's a different story.

If I was going to do it to the Enfield engine, I would not use the existing pumps, you are far too likely to cause serious problems (by overloading the pump, or destroying the pump if the cooler lines become blocked, ever).

Instead, I would tap in somewhere in the casing and use a 12v electric scavenge pump to move the oil through the cooler. That way there is no extra load on any mechanical system. If the pump fails, nothing is damaged. You can also include a thermal or pressure valve and a bypass in case of line clogging.

« Last Edit: June 13, 2008, 07:03:01 PM by geoffbaker »

mike704

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Re: external oil filter
« Reply #9 on: June 13, 2008, 10:31:01 PM »
Peter,
Have you upgraded to the high-volume oil pump, or does the stock pump push the oil through the fliter with enough pressure?
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Peter

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Re: external oil filter
« Reply #10 on: June 14, 2008, 03:19:54 AM »
No, I don't have the higher volume pumps and I have the stock big end bearing.
The spin-on oil filter I'm using is not going to create any appreciable additional back pressure for the standard scavenge pump flow.
How do I know? Well, I don't. I guess it would start smoking and throwing oil out of he breather if it can't keep the sump dry.

I actually don't worry at all about the back pressure. I'm more concerned about the additional connections which could fail and dump my oil. No failure yet after 2000 miles.   

Peter

oldsalt

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Re: external oil filter
« Reply #11 on: June 14, 2008, 06:19:08 AM »
... Plus, again just my opinion, the stock oil filter is a good one.  Just because it doesn't look like the one that comes on a Chevrolet or a Harley doesn't mean a thing.

Opinions aside, the stock oil filter is some kind of gauze and, on a good day, acts as a screen to keep larger shavings out of the big end.
The stock iron engine does not effectively filter its oil.

Peter

Irving, the designer of the Vincent engine, in his book Motorcycle Engineering had a different slant on these matters than is the common wisdom.  The big difference between the filter that is used on the RE and one for a Chevrolet is the type of service it must do.  The British engines, almost to a man, all have 'anti-friction' bearings at the critical points;  Big end of the rod and crank bearings and etc..  Most had no filter at all.  By anti friction it was ment rollers and balls.  Babbit bearings can't digest hard particals worth a damned.  Balls and rollers of various types don't care about the fine stuf that kills precision fitted inserts.  My opinon:  The stock filter is just fine.  Regarding fooling around with different filters in a system that has proven its self to work well?  Be carful.  You will be experimenting.  Again, this is my opinion, but I came by it the hard way.   
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Bankerdanny

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Re: external oil filter
« Reply #12 on: June 14, 2008, 02:12:00 PM »
In all the posts I have seen here I don't recall anybody talking about an engine failure precipitated by particles in the oil.

Given the oil change interval recommended by many people here (including Vince) of 1,000 miles, it hardly seems like the oil has time to get very dirty or that particles are around long enough to do much damage.

However, I think that an oil cooler would make sense for a long trip plus an upgrade to the high flow oil pumps.
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Re: external oil filter
« Reply #13 on: June 14, 2008, 08:09:09 PM »
... The British engines, almost to a man, all have 'anti-friction' bearings at the critical points;  Big end of the rod and crank bearings and etc..  Most had no filter at all.  By anti friction it was ment rollers and balls.  Babbit bearings can't digest hard particals worth a damned.  Balls and rollers of various types don't care about the fine stuf that kills precision fitted inserts. ...

FYI, the stock iron Bullet big end is a fully floating bushing, no balls or rollers there. This type of bearing does not like particles.
The standard filter will be able to keep the rats and mice out of that bearing but not more.
One of the benefits of an inline oil filter in the return line is that when the big end goes south, the particles are caught before they are dispersed throughout the engine causing accelerated wear everywhere. You can ride quite a while without knowing that the big end is going bad and spilling swarf. The filter contains the damage in the crankcase.

Peter
« Last Edit: June 14, 2008, 08:24:15 PM by Peter »

Peter

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Re: external oil filter
« Reply #14 on: June 14, 2008, 08:36:06 PM »
In all the posts I have seen here I don't recall anybody talking about an engine failure precipitated by particles in the oil. ...


Unfortunately, failure of the Bullet floating bushing big end bearing is not unheard of and there are some aftermarket solutions which are sold by our host.
The stock big end bearing is the main concern when it comes to proper oil filtering. The second major concern is valve train (rockers, cams etc.) wear which is addressed by filtering the returning contaminated crankcase oil on its way to the rocker boxes.

Peter

oldsalt

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Re: external oil filter
« Reply #15 on: June 15, 2008, 08:09:30 AM »
... The British engines, almost to a man, all have 'anti-friction' bearings at the critical points;  Big end of the rod and crank bearings and etc..  Most had no filter at all.  By anti friction it was ment rollers and balls.  Babbit bearings can't digest hard particals worth a damned.  Balls and rollers of various types don't care about the fine stuf that kills precision fitted inserts. ...

FYI, the stock iron Bullet big end is a fully floating bushing, no balls or rollers there. This type of bearing does not like particles.
The standard filter will be able to keep the rats and mice out of that bearing but not more.
One of the benefits of an inline oil filter in the return line is that when the big end goes south, the particles are caught before they are dispersed throughout the engine causing accelerated wear everywhere. You can ride quite a while without knowing that the big end is going bad and spilling swarf. The filter contains the damage in the crankcase.

Peter

Not a full floating babbit insert and not really troubled by particulates.  Many motorcycle engines used this sceme.  Especially Ducatis, Gileras to name a couple of successful designs.  I am surprised by your lack of confidence in the stock oil filter.  I suppose you have reasons.  However, it is true...balls and rollers can and do suffer contaminates much, much better than babbit inserts such as commonly used in an automotive engine.
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Peter

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Re: external oil filter
« Reply #16 on: June 15, 2008, 03:34:28 PM »
...
Not a full floating babbit insert and not really troubled by particulates.
....

You are really making it up as you go aren't ya.
You may want to read your posts in this thread in the order you posted them.
Kinda funny isn't it.

In any case, the iron Bullet engine big end bearing is a fully floating white metal bushing and it don't like particulates.

Peter

Foggy_Auggie

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Re: external oil filter
« Reply #17 on: June 15, 2008, 04:51:43 PM »
...
Not a full floating babbit insert and not really troubled by particulates.
....

You are really making it up as you go aren't ya.
You may want to read your posts in this thread in the order you posted them.
Kinda funny isn't it.

In any case, the iron Bullet engine big end bearing is a fully floating white metal bushing and it don't like particulates.

Peter

The CONNECTING ROD big end bearing is the bush.  The crankshaft is supported by ball and roller bearings.

The crankshaft timing side is a roller.  The crankshaft driving side is a paired ball bearing and a roller bearing.

The connecting rod big end is a floating bushing.  And is the first point in the oil supply path from the oil pump.

Just to save confusion for those that don't know.  And not to have a "gotcha" game here on this forum.
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Peter

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Re: external oil filter
« Reply #18 on: June 15, 2008, 05:36:16 PM »

The CONNECTING ROD big end bearing is the bush.  The crankshaft is supported by ball and roller bearings.

.....

The connecting rod big end is a floating bushing.  And is the first point in the oil supply path from the oil pump.


And this white metal floating bushing big end bearing is the main point of creating an effective means of oil filtration. Plain bearings require a steady supply of pressurized clean oil and the Bullet big end bearing is a variation of a plain bearing - not more and not less.
Insulating the rest of the engine from the swarf created by a disintegrating big end bearing is a bonus benefit if the filter is placed in the rocker feed line.

That's pretty much the rationale why someone may consider an external filter.

That's all there is to it, take it or leave it.

Peter

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Re: external oil filter
« Reply #19 on: June 15, 2008, 05:55:33 PM »
....

However, I think that an oil cooler would make sense for a long trip plus an upgrade to the high flow oil pumps.

My external oil filter only gets warm even on long rides in hot weather. So I doubt that an oil cooler will be of additional benefit when spliced into the rocker feed line.
High volume oil pumps are not necessary with the stock big end bearing and may load the worm drive unnecessarily. As long as the bearing is good, they won't push more oil through there. Roller bearing modification is another matter. If I ever have to do that, I'll put high capacity pumps in there at the time. Somebody I trust with these matters told me that a big end roller likes to be cooled by the oil flowing through. With rollers in place, loading the worm drive is not a issue because there's hardly any resistance across the bearing - very different from the stock bearing.

Peter

meilaushi

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Re: external oil filter
« Reply #20 on: June 16, 2008, 11:11:09 PM »
I'm not sure about any necessity for an oil cooler on these engines.  I just had mine up to L & L (Matt Lockso) for a 500 mile service (his recomended mileage for first service), and I warned him when he began to unscrew the plug in the bottom of the engine oil reservoir that he was going to get burned if he wasn't careful as the bike had just been run for 2 hours to get to his place from where I live.  He said he'd recently had another RE owner in for their 500 mile service and they warned him too, but he had no need to be warned, as the oil would not be hot, but only warm.  And so it was.  He said these bikes do not heat up oil like some others as, for instance, the Japanese ones that require oil coolers.  He was right about the oil being just lukewarm after a constant 2 hour run.  That would also mean the oil breaks down less quickly than it would in an engine that really heats it up.

Don't know how much help this information is, but it certainly seems accurate.
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Peter

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Re: external oil filter
« Reply #21 on: June 16, 2008, 11:50:54 PM »
...  That would also mean the oil breaks down less quickly than it would in an engine that really heats it up.

Don't know how much help this information is, but it certainly seems accurate.

Unfortunately, the places where the oil breaks down are the cylinder walls and possibly the hot head around the exhaust valve. Air-cooled engines are harder on the oil. I've got an alloy cylinder which is lapped to the head, so there is a good conduit for heat transfer from the head. But still, oil breakdown is a real issue, regardless of the temperature of the oil in the tank.
The discussions about oil coolers for RE's have been mostly about additional cooling of the head. I can't see that this would be achieved to any meaningful extent with a cooler in the return line when even a filter in that location only gets warm..
But who knows...

Peter
   

oldsalt

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Re: external oil filter
« Reply #22 on: June 17, 2008, 05:50:01 AM »
Again, to paraphrase Irving, the designer of the Vincent one liter twin:  'The designer of an overhead cam air cooled engine, if pressed, will admit that much of the head cooling is done with a copious supply of oil'.  He went on to discuss push rod and other designs such as the Parilla Wild Cat high cam design which is a compromise between the two.   Not only was he an ace engine designer but he had a way with words.  It is a fact that an overhead cam vertually eliminates head cooling in air cooled engine.  That is why the rice grinders and etc that boast that they have overhead cams also are generally liquid cooled and pack around an oil cooler ta boot.  That adds a lot of weight, cost and complexity to the engine design.  Reason number 97 why I much prefer my RE thumper to a so called high tech design.  The RE engine will not torture the oil like a lot of other engines.  Forget synthetics, oil colers, and extra filtration.  If there were any real reason to be doing these things Ariel, Norton, BSA and RE, to name a few British thumpers, would have had them hanging all over the bikes.   Leave it alone and spend your time riding. 
« Last Edit: June 17, 2008, 05:51:45 AM by oldsalt »
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Peter

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Re: external oil filter
« Reply #23 on: June 19, 2008, 09:37:06 PM »
Here is a source for external oil filters which may look a little bit more period, in case you care.

http://www.britishspares.com/16.php

I finally remembered where I saw those.


Peter

oldsalt

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Re: external oil filter
« Reply #24 on: June 20, 2008, 06:52:16 AM »
...
Not a full floating babbit insert and not really troubled by particulates.
....

You are really making it up as you go aren't ya.
You may want to read your posts in this thread in the order you posted them.
Kinda funny isn't it.

In any case, the iron Bullet engine big end bearing is a fully floating white metal bushing and it don't like particulates.

Peter

Peter
I'm sorry if I have upset you.  But it's not true that I am making it up as I go along.  However, I took your advice and reread all the posts.  But I didn't see anyting 'kinda funny".  We all have our reasons for haveing diverse viewpoints.  Mine is largely formed by being a mechanical engineer for more than 40 years.  My speciality has been power transmission.  If you are sure that the big end bearing is in fact a steel backed precision babbit bearing [like in a an early production 36 Ford engine] I am willing to believe it.  But if you feel I made up out of whole cloth the statements on oil cooling [the fact that a canister or tank will provide little useful cooling due to the vugarities of fluid mechanics] you are simply mistaken.  If you think it is funny that overhead cams greatly hinder head cooling, and that a renound motorcycle engineer uttered thes words, you would, again, be mistaken.  Lastly,  if you are sure that a stock RE filter is of poor design, I can but repeat what I said in a previous post; "--I suppose you have your reasons".  But allow me to say that I have my reasons when I say the filter is perfectly adaquate.
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LJRead

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Re: external oil filter
« Reply #25 on: June 20, 2008, 06:13:06 PM »
This has been a reassuring thread to me, since I know so little about bike mechanics.  Being new, mine runs so darn well, I feel like not ever doing anything to it for fear of messing something up.  But then, in my inexperience, I see people adding oil filters, and think that is something I maybe need.Now I know I don't need to do that, especially for my 350 cc bikes.

I know there will be some who want to maximize the output of these bikes, it being in their nature to do so, and who am I to begrudge them that?

But for me, it should be a rule to leave well enough alone.

As for taking one of these bikes cross country, I don't think I would be tempted to do that unless it could be done slowly on slow sorts of roads. 

One thing that would concern me is the standard piston of the 500 cc bikes, and that, I believe, should be changed out for something better in order to preclude problems in the future.  It seems a little like a time bomb waiting to explode, if what people say about them is true.  But I'll just trust the designers of Enfields with regard to oil filters.


PhilJ

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Re: external oil filter
« Reply #26 on: June 20, 2008, 09:31:12 PM »
LJ, I think that attitude is a result of "slowing down". When I was the age of a lot of the guys and gals wanting to get the max out of their machine, I would have been ordering parts right and left. Now, it just purrs along and clatters and knowing that is what it does, I simply smile, relax, enjoy the ride and say "been there dune that". I also found, the hard way, that the more I did, the more it broke. :o

Peter

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Re: external oil filter
« Reply #27 on: June 20, 2008, 10:38:43 PM »
...  If you are sure that the big end bearing is in fact a steel backed precision babbit bearing [like in a an early production 36 Ford engine] I am willing to believe it.

I've never said such a thing and why would you want to believe something like that?
The iron Bullet engine big end bearing is a fully floating white metal bushing. Just a variation of a plain bearing or fluid bearing.

...  Lastly,  if you are sure that a stock RE filter is of poor design,...

First of all, you need to realize that there is no general stock RE filter. The AVL engine has a proper stock oil filter element which doesn't fit the iron engine. The oil filtering of the AVL engine is one of the more important improvements of that engine over the iron engine. The iron engine oil filter was never upgraded and is still a gauze (or felt) element which is not of "poor design" but will work within its design limitations - which are wanting.


However, I took your advice and reread all the posts.  But I didn't see anyting 'kinda funny".

Now that's funny.


Now some more musings of some relevance to the subject.
Plain fluid bearings like the iron big end are supposed to run without metal contact once run in. With pressurized oil feeds the time to built up the layer of fluid upon startup is minimized provided that oil starts to flow into the bearing journal immediately. For that to happen, the oil feed passages need to be filled with oil. Unfortunately, the oil filter chamber is part of the oil feed passages. This is not much of an issue for normal startup but is a big issue for initial startup after a filter change. After a filter change, the chamber is empty and has to fill before oil starts flowing through the big end bearing. That's where the recommendation to idle the engine for 5 minutes after an oil and/or filter change comes from. Even if you do that, during the first couple of minutes the crankpin and the conrod with the soft white metal bushing between the two will be crashing onto each other. Lots and lots of wear.
What can you do about that?. Well, you can reduce the volume of the oil filter chamber by using the packing piece our host sells (maybe get the magnet as well). That will reduce the time until full oil flow is achieved. If you really want to eliminate the problem you need to turn the engine without load until oil flow is confirmed. Some just pull the decompressor and disconnect one banjo bolt at the head and kick it over until oil starts to flow out of the rocker feed line. other remove the plug and do the same. Again others, including myself, loosen the banjo bolt, put the tranny in gear and walk the motorcycle without plug until oil starts coming out. Don't forget to start with a drained sump.

Just some suggestions for big end protection which do not involve additional filtering.

Peter


« Last Edit: June 20, 2008, 10:41:50 PM by Peter »

LJRead

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Re: external oil filter
« Reply #28 on: June 21, 2008, 12:21:47 AM »
No PhilJ, age doesn't have much to do with it, I have just always liked moving in the slow lane.  Two things about the roads here, they are narrow and the sides are entirely bush covered, like a green wall.  So when you move along slowly, you hear a nice, deep throated thump, but if you move too fast, even just 40 mph, you get bush rush, and just see things sort of rushing by.  No fun at all.

If I were to drive long distances in the U.S., I wouldn't mod up an R E, rather I'd buy something like a used Honda - Iike one called the Honda Pacific Coast - totally different than the R E , but it looks nice to me and is functional.  There are very good looking used ones, routinely, on Ebay for about $4,000 with low mileage and mostly older owners, so they look to be straight.

The other thing is that because I like an unstructured life style, I have never had a regular job for any length of time, nor enough money to throw into speed equipment.  I retired from working for others about age forty and never looked back.  So I poke poke along, enjoying life immensely, but largely just making do.  Gets to be a habit.

Like I say, if someone wants to add a bunch of mods to their R E, well good on them - me, I'd get something that would go fast from the get go.



All this modification business, besides being expensive, doesn't make much sense to me. 

oldsalt

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Re: external oil filter
« Reply #29 on: June 21, 2008, 07:06:49 AM »
Peter
Why do you feel the need to be so crass? Just couldn't help yourself, had to reuse the the "funny" comment.  I'm here because I like my RE.  If I have angered you by infering that the filter that you put in the rocker box line is at best experimental, again I am sorry.  I have spent my whole working life as an engineer, mechanical engineer.  I sure don't know it all, but I do have a working knowledge of bearings.  I have worked with some very fine, on the leading edge engineers and have never, no matter how off the mark my question was, been greeted with "Funny" comments.  So here we go again.  Realizing  there is a definate difference between sliding surfaces that operate in a hydroststic and hydrodynamic mode.  I assumed that the big end  was a copper/tin/zink variety as that is the normal choice [and there is a lot of motorcycle history in this] for a big end full floating bearing.  They almost always funtion in a hydrostatic mode.  Generally, in this type of application and service a white metal [tin/lead and etc.] bearing is used when hydrodynamic running is possible.  But, and in my mind here is the rub, an RE pump will not put out enough pressure to reliably provide a hydrodynamic condition.  Hydrostatic is used when  'full film' lubrication is desired but hydrodynamic operating conditions can't be attained. So I'm still wondering and learning.  If you wish to enlighten me, please do.  We know for sure that the bearing operates somewhere between 'mixed' and 'full film'.   

   
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LJRead

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Re: external oil filter
« Reply #30 on: June 21, 2008, 07:35:23 AM »

. Even if you do that, during the first couple of minutes the crankpin and the conrod with the soft white metal bushing between the two will be crashing onto each other. Lots and lots of wear.
Peter
Just a quick question to underscore my own ignorance.  This idea that when a bike has been setting, maybe overnight or even longer, or when the oil is changed, then all the oil drains from the inner bearing surfaces - is that true?  I would have thought there would be a residual film of oil remaining there until new oil takes over.

Foggy_Auggie

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Re: external oil filter
« Reply #31 on: June 21, 2008, 03:29:23 PM »
a copper/tin/zink variety as that is the normal choice [and there is a lot of motorcycle history in this] for a big end full floating bearing.  They almost always funtion in a hydrostatic mode.     

You are right oldsalt.  I've never seen a RE connecting rod bush, but somebody who has says it looks just like bronze.  And it has rounded edges almost like a donut.

And copper/tin/zink are the alloy components for both brass and bronze.  Probably the best properties of both.  And a good hydrostatic match for a mild steel crankpin.  Also can survive minor oil contamination.

The Bullet oil pump is a very low pressure system which also supports the above.  The common automotive shell type bearings (babbit/white metal) requires a high pressure oil system.
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Fortiter Et Fideliter

Peter

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Re: external oil filter
« Reply #32 on: June 21, 2008, 05:27:45 PM »
  Realizing  there is a definate difference between sliding surfaces that operate in a hydroststic and hydrodynamic mode. ...
... We know for sure that the bearing operates somewhere between 'mixed' and 'full film'.   


The Bullet iron engine big end bearing is a fluid bearing in form of a floating bushing arrangement and oil is supplied via an orifice in the crankpin. This makes it a fluid bearing of the hydrostatic type. The fact that the oil pressure of in the Bullet is low does not change the mode oil is supplied to the bearing: Directional flow along a pump generated pressure gradient. Bear in mind that the rotating crankshaft is to be considered part of the pump due to the accelerating oil column in the flywheel bore.
The existence of an oil feed pump and the rotating crank and, for completeness, the subatmospheric pressure in the crankcase must result in a pressure difference between the oil tank and crankcase. If your Bullet is not equipped with a working overpressure release valve, all circulating oil flows along this gradient  through the big end bearing.
The placement of the big end bearing in line with the oil flow defines the bearing as a hydrostatic fluid bearing. The steepness of he driving pressure gradient is not relevant. The only thing what makes a bearing a hydrostatic fluid bearing is that the pressure gradient (also known as "hydrostatic" gradient, duh) is utilized for oil supply.
Hydrodynamic fluid bearings do not have a directional oil supply. Fluid layer thickness is maintained by the bearing movement itself. For obvious reasons, you won't find an open hydrodynamic fluid bearing in a dry sump engine.

So now we got this squared away:
Classification of a fluid bearing as a hydrostatic or hydrodynamic fluid bearing is strictly based on the mode of fluid supply.
Hydrostatic fluid bearings utilize a hydrostatic gradient for oil supply and because it is rather difficult to create a physical hydrostatic gradient in an engine application, pumps are generally used to create the functional equivalent.
Hydrodynamic fluid bearings do not utilize a hydrostatic gradient or its functional equivalent but rely on hydrodynamics alone for replenishment of the fluid layer.

Unfortunately, the plot thickens a bit when we consider how the fluid layer separating the surfaces is maintained during normal operation of a fluid bearing. At that level, inside the operating bearing, fluid bearings of either type operate on hydrodynamic principles. Yes, that's right. Hydrostatic and hydrodynamic bearings both operate hydrodynamically under normal conditions.
There is a hydrostatic effect which is detrimental when it occurs and that is when channels of fluid flow occur and disrupt the hydrodynamic condition. Fluid bearings never operate in "hydrostatic mode". They operate in hydrodynamic mode during normal operation, in mixed and/or boundary mode during startup and when operated beyond design specification. Finally they may operate with full contact under dry conditions which is bad and for which additives are contained in engine oil to save things if this occurs transiently.

I have not yet had to look at my big end bearing so I do not know what it looks like. All I can say is that the Bullet Workshop Manual page 30 says that it is a white metal floating bushing.

I wish everybody an uninterrupted oil flow supported by a stable hydrostatic equivalent pressure gradient and a fully hydrodynamic condition in their big end at all times.

Peter


 
« Last Edit: June 21, 2008, 05:32:46 PM by Peter »

oldsalt

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Re: external oil filter
« Reply #33 on: June 22, 2008, 02:13:23 AM »
Peter

Thank you sincerely for going to the trouble to continue my education.  Your concise account of what goes on at the big end was enlightening and welcome.  It always makes mechanical things more interesting when the phenomenon of their funtion is understood.  In any case, the fact that the lower end of a RE is basicly unchanged since the 50s makes me like it even more. 
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