The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: Johnhayesuk on 01.10. 2018 10:36
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Hello my fellow experts, (not me)
Ignorance is bliss ! Where is the sludge trap on my 1952 A7 I have removed drain plug and mesh filter at bottom of engine and removed all oil from oil tank on r/h side including filter but where is this sludge trap! And what oil if the jury has returned a virdict Yore all so beautiful
John
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......Yore all so beautiful
John ....
Well maybe the others are but I'm not as I have the news you don't wish to hear... the sludge trap is in the bowels of the crank, which entails deep surgery to access.... is under the big-ends.... sorry, they didn't like me at school either
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Hello, yes, inside the crank & needs disassembling of engine.
see https://www.a7a10.net/forum/doc/parts/BSAA7_A10_1949_to_1953_Spares.pdf
page 11, location behind the 'plug', part 58
When you are at it, after opening Spares.pdf, save it to your computer, so as to always have it available.
Use search, sludge trap, lots of good reading and info about this important maintenance task (thankfully not often it's needed, but if maintenance history of engine is not 100% known, sludge trap has to be checked).
I remember mine, was nearly full of 'something' that had completely petrified like cement, oil flow must have been getting close to nonexistant. Glad I checked and cleaned it.
Direct link to sludge search results (https://www.a7a10.net/forum/index.php?action=search2;params=eJwtzUEKwyAUBNCrlG66mUW-GtPbiNFP02JjUJNS8PDVkt3Mg2GsP-zq2NdbHeq1zqmnEfIOqSAnCAmhQRI0gRRIQw2QBCFAI5Rum7zEj3HxvQUu3Nad9vnFrpi4hu8pMZWWEgf-H55k_DM19pxdF7bJLa3nsPsHX0qy2w8IcTcr)
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May be a bit late now, but here are a few pictures of a clogged sludge trap and a crankcase showing the consequences of not cleaning it out. Any help needed, just ask. Sleep tight! Swarfy
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OMG I can see I shall have to do a cleanout on Josef's A10 before reassembly. I have the crank out already, the sludge trap plugs don't have any slot in them however. Maybe I'll drill them in the middle and try a fat thread extractor. But once I have them out, this is an early crank so no tube in it, how shall I ensure I've got all the sludge out??
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.....how shall I ensure I've got all the sludge out??...
Fairly self evident, you won't see anything other than a hollow, but ensure you clear the gallery between the main journal and big ends-I used a wire brush from a gun shop..... Replace the plugs with socket wrench types, like SRM sell.
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Replace the plugs with socket wrench types, like SRM sell.
When putting the new plugs in make sure they are not inserted too far and so partially blocking the oilways.
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Hi Steverat...If any single aspect of the design of the A10 has ever been neglected or misunderstood, it is the "Sludge Trap". On a small journal crank it really is just just a simple oilway leading from one big end to the other. Unfortunately this is where all the low life found in your motor congregates to cause trouble. This is how I do small journal cranks. Basic technique applies to big journal cranks, but they have a tubular trap that really does trap the sludge.
I will assume you have some basic knowledge, you may be a time served machinist, apologies if this is a trip down memory lane.
First, measure the journals. Has the crank any life left? Is it worth proceeding. Can you get new bearing shells?
If your plugs have no slots, that is unusual. How would they be turned into place? Could they be some just some bodge by a previous owner, like a couple of metal corks hammered in?
Have a good dig, there should be a slot across the middle, plus 2 or 3 punch marks to lock the plug in place.
Getting them out is easy. First treat yourself to a new set of drills. My favourites are a cheap set of cobalt drills from Toolstation.
Support the crank well, and talk to it. Let it know you have a new set of drills, you are in no mood to be gentle, the end of the world is coming, and you, plug with no married parents, are coming out.
The aim is to create the least amount of damage, so we start gently and work up into a frenzy of violence and desperation no plug can resist.
Next, drill very gently into the punch marks with your smallest drill. The aim should be to remove metal from the plug, not the crank. When you have done some exploring, drill the punch marks with bigger drills until you are sure they are no longer effective, making sure you do not drill the crank.
Now you need the biggest flat blade screwdriver......I use one on a 1/2" square socket drive. With the crank well supported, put the blade in the slot and give it a good smack to let the plug know the pain is coming and jarr the thread and hopefully help start it on its way out. No luck? Try an impact driver, but the blade size on these is smaller and you may damage the slot.
Next, try a bit of heat. Butane, Propane torch, Oxy- acetylene if you have it. This is where I generally have success and out it comes, normal right hand threat, lefty loosey anti clockwise to undo.
No slot, or slot already wrecked? Drill a nice hole in the middle but do not use a stud extractor. Typically these spread the plug further the deeper they go so will tend to make it more difficult to remove.. Instead try a big TORX bit, hammered into a slightly smaller hole. Still no good? If you feel confident, put a bolt in the hole and and tack weld it to the plug. The heat of welding a bolt to the plug will help loosen it and you also have something to put a spanner on.
Still no good? Big Drill Time!. Enlarge the centre hole with your ever increasing size selection of new drills until you are left with just a thin threaded cylinder, thin enough to collapse into the hole.
Remember, try not to damage the crank. Before grabbing a well deserved beer, take a few pictures to remind you of one of the most memorable days of your life.
You will be amazed at the small size of the oilway. Easy to clean, just a straight drilling. New plugs are available, or get some made, thread size somewhere on this Forum.
Good Luck with it.
Keep Spannering, Swarfy.
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I couldn't find any hex plugs for my 1951 A7...slotted were the only ones available.
Due to either/or the replacement plug thread not fitting nicely with the 67 year old thread in the crank I had to lap the new plugs in until they were able to be screwed flush. I had to index the plug with the crank oil way and remove some metal from the plug to prevent the plug partially obscuring that oilway too.
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Rex, Thanks for that timely reminder concerning the quality of replacement parts. As Greybeard remarked, screwing a plug too far in will obstruct the oil feed to the journals. Good job you noticed , lots of folks wouldn't. Shame they can't be made right first time. It would be more profitable, thinner plug, less material. Balance factor? Out of balance from standard anyway, once the carbon is on the piston crowns.
Swarfy.
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Thanks Guys,
Josef's plugs were blank, no slots. So I had to drill the centre for an extractor. Lucky me - they came out without too much swearing. SRM have promised to send some new plugs with hex sockets so thats all nice.
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Well they were not meant to come out easily were they. Must have screwed in a stud or bolt and just hack-sawed the end off
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Steve, you are indeed a lucky man. Here's me thinking you would need a bit of help. Bear in mind there are two sizes of plug, Small Journal...Small Plug.. Big Journal Cranks have a bigger diameter. Hope you have ordered the right ones. What did you find?
Swarfy.
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Thanks Guys,
Josef's plugs were blank, no slots. So I had to drill the centre for an extractor. Lucky me - they came out without too much swearing. SRM have promised to send some new plugs with hex sockets so thats all nice.
How much muck was under those plugs?
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There was a teaspoonful of sludge altogether - enough to be dangerous I think.
Yes got some new plugs with hex sockets for small bearing cranks from SRM. They were very good and quick too, the plugs are here already.
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On a related subject,
Has anyone measured the density of the typical crud removed from the sludge trap.? You know - weight and volume of the dry crud. Otherwise anyone hazard a guess.?? Or the typical mixture of metal, atmospheric dust (silica and alumina?), carbon (carbon black may be similar?) Hardened oil,? Just ballpark numbers would do.
I had my crank balanced many years ago before the internet and this Forum, when I also had no idea what 70% meant. I recently checked the receipt, and it does say 70% BF. That number sounded good at the time.
After enquiring whether the workshop had removed it for cleaning, "No we blew it out with compressed air". So I removed and cleaned it. It was more than half full. It had clearly been blown out with compressed air, but the remaining crud was dry and hard, having been idle for some 15 or so years.
On calculating my balance factor yesterday (with clean sludge trap), I got a BF of 55.4 using same pistons, rings, rods, gudgeons & circlips.
I think there was sufficient crud in the trap to explain the difference. My spreadsheet suggested that about 80 grams would explain it. I measured 30 mls capacity of the sludge trap, but the density or SG of the crud would be helpful in making sure I am on the money. It will be much higher than the SG of oil no doubt.
On the positive side, the bike has done 80 miles since re-commissioning, and had been running smoothly up to about 60mph, so I am relieved that it wasn't cleaned first before balancing. My new pistons are lighter, so calculate a new BF of about 58.7, which is about where I think I want it.?
Hopefully I will be well-armed to talk to my new engineering shop about what to do.
Cheers
Col
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G'day col.
That's a question for a mastermind (certainly not me). SG of water is 1 so 30ml = 30g. If the trap was 1/2 full = 15g. Now the SG of the sludge would be 15g if it was water. SG of oil is 0.9, aluminum is 2.5, carbon is 2.1, cast iron is 7. So saying 25% of each would give a SG of 3.125 x 15 = 46.87g.
Std is 54% or there abouts and 65% for racing. At 70% it would walk out the door backwards if on the c/stand at anything over idle DAMHIK.
Cheers
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I suppose to be absolutely accurate, the crank should have the oilways full of oil when measurements and comparisons are being made, but in any event the balance factor is related to the rotational speed. In other words there will always be a sweet spot, with the least vibration and mechanical clamour and the position of this on the speed range will vary with the balance factor used.
Also in theory the sweet spot will change over time, as the sludge accumulates and the balance factor changes. It also changes as the pistons carbon up, but whether these changes are important is subjective, your rough old dog may be considered a smooth ride by someone worse off. In fact depending what you start with, it may smooth out or roughen up at your favourite riding speed.
As for the composition of the sludge, a few varied samples and access to your local neighbourhood Spectrophotometer and Gas Liquid Chromatograph will sort that one out.
Swarfy.
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It is the dynamic balance that is important, not the static
And yes everything has to be taken into account right down to things like the center punches in the sludge plugs, and of course the actual sludge plug.
A hex one is substantially lighter than a standard slotted one.
However as you are not building a Daytona racer I would not get too upset about it
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G'day Swarfy.
I agree about sweet spots but trying to keep it clean. *grins*
My A7 racer was smooth as silk at 6000rpm and up. I think it was up around the 72% mark. But at that speed I was more concerned with getting around the corner *problem*
Cheers
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G'day Trevor.
Some of us don't have access to dynamic balancers ( I lived 8 miles from 240v power). Mine was static with the oil galleries filled with 25w oil and plugged with wax.
Under 4 grand it'd shake my tooth fillings out.
Cheers
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Thanks Fellas,
Musky, I also did similar guessing at the components in sludge. Bit too hard, as most of the components would have reacted with each other over the years and formed What knows.??
It is so smooth up to 60mph that there is no doubt the actual BF is quite low.
Anyway, I am getting it dynamically balanced, so hopefully I will end up with BF somewhat less than 75%. He He.
Col