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Thread: The Bucket Foundry

  1. #4231
    Join Date
    10th February 2005 - 20:25
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    1944 RE 1
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    Auckland, New Zealand.
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    Quote Originally Posted by Grumph View Post
    Constraining the pin is relatively easy. Either full blind ends in the clamping pieces or partial "eyebrows" - neither of which would present a major machining problem.
    Or - if locktabs are used for the screws - extend them over the edge so to speak and use them to retain the pin.
    Yes, a couple of relatively easy solutions there
    - possibly still need to retain the end of the tab though? (to be sure).
    Freedom of speech is important but if what we say is considered incorrect by our peers, they will quickly put us right.
    P.C. will eventually destroy our right to tell the truth.

  2. #4232
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    19th October 2014 - 17:49
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    whatever I can get running - dirt/track/
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    Greg, there's not only Brinelling, but also false Brinelling.

    https://en.wikipedia.org/wiki/Brinelling

    https://en.wikipedia.org/wiki/False_brinelling

    cheers,
    Michael

  3. #4233
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    19th October 2014 - 17:49
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    I was reminded that not everyone has a fast Internet connection:

    Introduction
    Brinelling is a material surface failure caused by Hertz contact stress that exceeds the material limit. It usually occurs in situations where a significant load force is distributed over a relatively small surface area. Brinelling typically results from a heavy or repeated impact load, either while stopped or during rotation, though it can also be caused by just one application of a force greater than the material limit.

    Brinelling can be caused by a heavy load resting on a stationary bearing for an extended length of time. The result is a permanent dent or "brinell mark". The brinell marks will often appear in evenly spaced patterns along the bearing races, resembling the primary elements of the bearing, such as rows of indented lines for needle or roller bearings or rounded indentations in ball bearings. It is a common cause of roller bearing failures, and loss of preload in bolted joints when a hardened washer is not used.[1] For example, brinelling occurs in casters when the ball bearings within the swivel head produce grooves in the hard cap, thus degrading performance by increasing the required swivel force.

    Avoiding brinelling damage
    Engineers can use the Brinell hardness of materials in their calculations to avoid this mode of failure. A rolling element bearing's static load rating is defined to avoid this failure type. Increasing the number of elements can provide better distribution of the load, so bearings intended for a large load may have many balls, or use needles instead. This decreases the chances of brinelling, but increases friction and other factors. However, although roller and ball bearings work well for radial and thrust loading, they are often prone to brinelling when very high impact loading, lateral loading, or vibration are experienced. Babbitt bearings or bronze bushings are often used instead of roller bearings in applications where such loads exist, such as in automotive crankshafts or pulley sheaves, to decrease the possibility of brinelling by distributing the force over a very large surface area.

    A common cause of brinelling is the use of improper installation procedures. Brinelling often occurs when pressing bearings into holes or onto shafts. Care must usually be taken to ensure that pressure is applied to the proper bearing race to avoid transferring the pressure from one race to the other through the balls or rollers. If pressing force is applied to the wrong race, brinelling can occur to either or both of the races. The act of pressing or clamping can also leave brinell marks, especially if the vise or press has serrated jaws or roughened surfaces. Flat pressing plates are often used in the pressing of bearings, while soft copper, brass, or aluminum jaw covers are often used in vises to help avoid brinell marks from being forced into the workpiece.[2]

    False brinelling
    A similar-looking kind of damage is called false brinelling and is caused by fretting wear. This occurs when contacting bodies vibrate against each other in the presence of very small loads, which pushes lubricant out of the contact surface area, and the bearing assembly cannot move far enough to redistribute the displaced lubricant. The result is a finely polished surface that resembles a brinell mark, but has not permanently deformed either contacting surface. This type of false brinelling usually occurs in bearings during transportation, between the time of manufacture and installation. The polished surfaces are often mistaken for brinelling, although no actual damage to the bearing exists. The false brinelling will disappear after a short break-in period of operation.[1]

    Fretting wear can also occur during operation, causing deeper indentations. This occurs when small vibrations form in the rotating shaft and become harmonically in sync with the speed of rotation, causing circular oscillations in the shaft. The oscillation causes the shaft to move in precession, and the timing of the rotation speed causes the balls or rollers to contact the races only when they are in similar positions. This forms wear marks caused by contact with the bearings and the races in specific areas, but not in others, leaving an uneven wear-pattern that resembles brinelling. However, the marks are usually too wide and do not exactly match the shape of the bearing, and therefore this type of wear can be differentiated from true brinelling.[1]



    False brinelling
    From Wikipedia, the free encyclopedia
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    False-Brinelling of a bearing
    False brinelling is a bearing damage caused by fretting, with or without corrosion,[1] that causes imprints that look similar to brinelling, but are caused by a different mechanism. False brinelling may occur in bearings which act under small oscillations[2] or vibrations.[3]

    The basic cause of false brinelling is that the design of the bearing does not have a method for redistribution of lubricant without large rotational movement of all bearing surfaces in the raceway. Lubricant is pushed out of a loaded region during small oscillatory movements and vibration where the bearings surfaces repeatedly do not move very far.[4] Without lubricant, wear is increased when the small oscillatory movements occur again. It is possible for the resulting wear debris to oxidize and form an abrasive compound which further accelerates wear.


    Contents
    1 Mechanism of action
    2 Simulation of false brinelling
    3 Examples
    4 References
    5 External links
    Mechanism of action
    In normal operation, a rolling-element bearing has the rollers and races separated by a thin layer of lubricant such as grease or oil.[5] Although these lubricants normally appear liquid (not solid), under high pressure they act as solids and keep the bearing and race from touching.[6][7]

    If the lubricant is removed, the bearings and races can touch directly. While bearings and races appear smooth to the eye, they are microscopically rough. Thus, high points of each surface can touch, but "valleys" do not. The bearing load is thus spread over much less area increasing the contact stress,[8] causing pieces of each surface to break off or to become pressure-welded then break off when the bearing rolls on.

    The broken-off pieces are also called wear debris. Wear debris is bad because it is relatively large compared to the surrounding surface finish and thus creates more regions of high contact stress. Worse, the steel in ordinary bearings can oxidize (rust),[9] producing a more abrasive compound which accelerates wear.

    Simulation of false brinelling
    The simulation of false brinelling is possible with the help of the finite element method. For the simulation, the relative displacements (slip) between rolling element and raceway as well as the pressure in the rolling contact are determined. For comparison between simulation and experiments, the friction work density is used, which is the product of friction coefficient, slip and local pressure. The simulation results can be used to determine critical application parameters or to explain the damage mechanisms.[10]

  4. #4234
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    10th February 2005 - 20:25
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    Guess that answers quite a few questions which I have asked about problems with all sorts of machines over the years!
    Freedom of speech is important but if what we say is considered incorrect by our peers, they will quickly put us right.
    P.C. will eventually destroy our right to tell the truth.

  5. #4235
    Join Date
    12th March 2010 - 16:56
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    TT500 F9 Kawasaki EFI
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    Hamilton New Zealand
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    finally can finish my piston off. My CNC lathe, best tool to use to get a nice accurate taper, has been out of action.
    It uses a small battery pack to power up the turret controller when the machine is turned off. Must be replaced once a year but last year it seems I was sold an out of date battery pack, so it went flat, losing its memory. Sufice to say it's expensive and a bitch to get it re memorized.
    All good again.

  6. #4236
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    12th March 2010 - 16:56
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    left side kick start plus counter rotating bob weight and a little sensor thing. 24 minus two pin wheel inside. Kick start leaver getting released from is block of 7075 aluminium.
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  7. #4237
    Join Date
    1st May 2016 - 13:54
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    Vintage 2T
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    Quote Originally Posted by Flettner View Post
    left side kick start plus counter rotating bob weight and a little sensor thing. 24 minus two pin wheel inside. Kick start leaver getting released from is block of 7075 aluminium.
    Very Cool, Is the bob weight concentric on the crank?

    Driven by Frits' "handful of gears" or something KISSier?
    (2 gears and a chain & sprockets perhaps)

    Forward Kick on the starter? or Bully style - left side, right boot?

    Cheers, Daryl

  8. #4238
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    1st May 2016 - 13:54
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    Quote Originally Posted by Pursang View Post
    2 gears and a chain & sprockets


    Cheers, Daryl

  9. #4239
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    12th March 2010 - 16:56
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    Hamilton New Zealand
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    its a three gear setup, crank turns reverse, an idler / bob weight at one to one in reverse ( the bottom shaft you can see) to the crank then a larger kick start gear meshing with this idler. Makes the kick start standard direction just on the wrong side of the bike.
    Next engine will be a 175cc , it will have just a simple pull start direct to the crankshaft, lightest and simplest start system possible.

    Kick start leaver is under manufacture still, buggered the first one up, lumps of 7075 are not cheap bugger it.

  10. #4240
    Join Date
    1st May 2016 - 13:54
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    Quote Originally Posted by Flettner View Post
    Next engine will be a 175cc , it will have just a simple pull start direct to the crankshaft, lightest and simplest start system possible.
    Rotary Valve Kwaka F7? CanAm/Rotax 175? Big Bore 'modern style' 125? or will you cast your own cases?

    Decompression valve or maybe 'full open' power valve for pull starting?
    I know that snowmobiles and the Rokon have pull starters, but even a recalcitrant little chainsaw can give a decent pull back.
    Victa fitted automatic decomp valves to their 160cc "easy start" mowers.
    It was not uncommon for big bore 2 strokes to have a small bleed hole drilled from higher in the cylinder wall into the exhaust port.
    Allowed a compression drop at starting speeds but no apparent HP variation at operating RPM.

    Cheers, Daryl.

  11. #4241
    Join Date
    12th March 2010 - 16:56
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    Daryl, you have to ask, cast it new of coarse.
    righ side RV, left side drive back to a countershaft one to one / balance shaft. In oil flywheel on the crankshaft outside this thin drive gear. Right side of balance shaft with another bob weight and the drive to the clutch. Set fairly high in the case to try to keep the engine from getting too long. RV cover now becomes a simple ish affair being just a cover.
    Twin exhaust ports rearward, mk2 TPI and possibly a left hand side crankcase port to open direct at high speed. Will use my new machined piston, maximim exhaust width, bridged port but each port exiting out its own hole in the cylinder. Exhaust right around to halfway round the cylinder. Cylinder held on with through bolts from underneath so as to not get in the way of any of the porting arrangements, just some short threaded boses cast in. Looking at 60.5 x 60.5 bore and stroke. Large dia RV using my sliding gib system for thottle and timing.

    Time and money, isn't going to happen any time soon.

  12. #4242
    Join Date
    1st May 2016 - 13:54
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    Quote Originally Posted by Flettner View Post
    you have to ask
    Neil, Had to ask, that way we got your great description of what your planning.

    (Lack of) Time & Money are inhibitors, but you have well proven that you have got what it takes to successfully get it done.

    Would be great if a factory got rid of a few bright young 'software' engineers (who seem to come out of Uni knowing Everything) and gave you some support instead.
    Practical experience, field knowledge and real understanding are increasingly devalued, so development is slow/no evolution rather than Quantum Leaps (end of Grumpy Old Man Rant).

    Following your progress with awe & respect.

    cheers, Daryl.

  13. #4243
    Join Date
    12th February 2004 - 10:29
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    If I win Lotto I'm going to build a big shed right next to Neil's place and pay him to do whatever he wants in the shed. Everything will be supplied. It'll be worth it.

    I can't figure out why someone hasn't turned up and started throwing money at him.

  14. #4244
    Join Date
    25th March 2004 - 17:22
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    Company money got spent enroute throwing money at strippers so they returned to factory and said, Solly, he no play nice.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
    Everybody listen, voices in my head
    Everybody listen, do yours say, what mine says?

  15. #4245
    Join Date
    28th November 2013 - 21:58
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    Think I've been Kiwibikered or Flettnered. First thought on seeing this was that he seemed a bit overdressed!
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