Die avonture van Gerrie en Lobo

[Gerrie]

Die ou wat my gehelp het weet hoe om gaskets te maak, so as dit nie nodig is nie, los ek die hubs soos hulle is... Anders meot jy dalk maar post Peter, dalk is daar iemand anders wat dit nodig het?

[JG Shields]

Gerrie, praat as jy nie regkom met die boute nie. Ek het 'n hele 5liter houer vol Nissan boute wat sekerlik daardie boute sal insluit.

[Gerrie]

Dankie JG! Tot dusver hou die gewone boute wat ek ingesit het nog. Ek het wel besef hoe belangrik split washers is. Daar was glad nie op gewees nie, maar het nou ingesit.
My plan is om vandag dalk weg te glip by die kantoor en dalk so paar goedjies te gaan koop... Nuwe boute, 'n gloeilampe vir die hooflig (die dim het gegroet - die brights werk nog!), brakefluid en LSD olie...
Kom nou Lotto-kaartjie...

[Peter Connan]

Gerrie

Pasop vir split washers. As hy reg ge-torque is, is split washers nie nodig nie, want die bout rek eintlik klein bietjie, en doen dus dieselfde funksie as die split washer. Verder voeg die split washer weerstand (wrywing) by gedurende die vasdraai-proses, wat maak dat die bout nie heeltemal so vas is op die selfde torque waarde as sonder die split washer nie.

Verder, tensy daardie gewone boute dieselfde gradering het as die korrekte boude nie, moet jy so spoedig moontlik van hulle ontslae raak, en verseker nie die hubs sluit terwyl hulle daar is nie, want hulle is waarskynlik nie regtig sterk genoeg om dir werk te doen nie. Die gradering van die bout of capscrew behoort op die kop daarvan te staan. Op Capscrews is dit nogal fyn skrif, jy sal moet mooi kyk.

For those that don't know, the bolt grading consists of two or three numbers, with a full stop before the last number. The meaning is as follows: the group of numbers before the full stop, whith two zeros added is the Ultimate Tensile Strength, in MPa (MegaPascal). Thus this is the stress value at which the bolt will break. When this number is multiplied by the full stop and the number after it (as a fraction), you get the Yield Strength (the point at which the bolt will be permanently stretched), again in MPa.

Thus a Grade 8.8 bolt will break at an induced stress of 800MPa , and will bend or permanently stretch at 800*0.8 = 640MPa. Compare this with a Grade 12.9, the comparative values would be 1200MPa and 1080MPa.

Now the trick is that a normal bolt you buy at Builder's Warehoouse is a Grade 4.6, whereas capscrews are only made in Grade 8.8 and better. And galvanizing makes this grade 4.6 bolt even weaker.

To get an idea of how much force a bolt can handle, you need to multiply the Yield Stress above with the effective cross-sectional area of the bolt at it's thinnest point (in square m), which is usually at the threads. to roughly determine the diameter at the root of the threads, you can subtract the thread pitch from the bolt diameter.

So if you are using an M8 x 1.25 bolt, then the root diameter is roughly 6.75mm. this gives a cross-sectional area of 0.0000358m^2. assuming a grade 8.8 bolt (as an example), this gives a force of 22 902N or 2 290kg

[Gerrie]

Oukei, so split washers is nie 'n goeie idee nie? enige washers?
Jip, dis my plan om daai ander boute so gou as moontlik (lees more!) te vervang... ek kon net nog nie by 'n plek uitkom vir nuwe boute nie...
Peter, wil jy nie maar Kaap toe trek en my kom help nie??

[David]

Gerrie
Soos Peter sê los die wassers - jy kan eerder bietjie Loctite of soortgelyk op die thread sit as jy bang is hulle gaan losgaan. Persoonlik dink ek nie dis nodig as jy die boute reg torque nie - Gaan belê 'n paar rand in 'n torque wrench of maak vriende met iemand wat een het

[Gerrit Loubser]

Pasop vir split washers. As hy reg ge-torque is, is split washers nie nodig nie, want die bout rek eintlik klein bietjie, en doen dus dieselfde funksie as die split washer. Verder voeg die split washer weerstand (wrywing) by gedurende die vasdraai-proses, wat maak dat die bout nie heeltemal so vas is op die selfde torque waarde as sonder die split washer nie.

I agree, The split washers are an archaic idea that has been found not to improve bolted joint reliability. A properly designed bolted joint should not give problems if the correct grade bolt, nut and washer is used and the joint is assembled by tightening to the correct torque (or following the correct torque-turn procedure if applicable) in the correct sequence.

Looking at the manual, it seems that the original setup should have had special washer plates, each being shared between two bolts:

Safari Hubs.jpg (151.2 KiB) Viewed 1878 times

[Gerrit Loubser]

Oukei, so split washers is nie 'n goeie idee nie? enige washers?

Die heel beste is om daardie snaakse plaatjies van Nissan te gebruik. As jy normale wassers gebruik, is die beste tipe verharde wassers, hoe dikker, hoe beter. Die dikker wasser veroorsaak 'n meer uniforme drukverspreiding onder die wasser, wat insinking in die onderliggende materiaal beperk en die harde oppervlak verminder die kans dat die bout of moer in die wasser kan insny en dus veroorsaak dat 'n deel van die wringmoment nie aamgewend word om die bout te rek nie. Die harde oppervlak bied ook meer weerstand teen kruip (die verskynsel dat die metaal stadig oor tyd deformeer weens 'n aangewende las). Kruip is een rede hoekom boutlaste kan loswerk.

[David]

... it seems that the original setup should have had special washer plates, each being shared between two bolts

Ek onthou my ou Safari het daai plaatjies gehad maar interessant genoeg my 2006 Patrol het niks

hub.JPG (37.35 KiB) Viewed 1869 times

Lyk my die manual hubs het die plaatjies en die auto hubs nie...??

[Peter Connan]

David indeed this is interesting. I beleive part of the reason is that the capscrews on the auto-lockers are considerably longer, and you will also notice that the maximum torque is higher.
The significance of the longer bolt is that it will have more flex, and therefore creep may be less of a problem. It is also possible that the hub casing is made of a different (possibly harder) material.

Gerrie I would use loctite on these bolts, for three reasons:
1) Loctite acts as a lubricant during tightening, and therefore the bolts will be more evenly tightened.
2) Loctite will prevent the threads from rusting.
3) If there was any possibility of the bolts loosening, loctite will prevent this anyway.