Do the volvo desiners have brain cells???

[Callum]

Started swapping my diff/gearbox over today. What a pig to do on your own! Main bit that i found stupid and some, was the brace bars that the diff mount to. Why they decided to use a nut and bolt and not captivate the bolt head is beyond me. Now that ive put the bars on the new diff it was a pain to get everything lined up right. Rant over!

Any tips for this job or any annoying jobs post them up

[Evoman]

Becuase on an assembly line you dont need to weld a captive nut in. Manufacture/assembly first, maintainence second.

[Ride_on]

No design is perfect for assembly or maintenance, this is an assumption made by someone who has spent hours over a particular job had problems with seized threads, corroded nuts. The designer did not have that amount to time to consider every little detail, may have been inexperienced or up against a deadline.

I normally leave all the bolts loose until they are all thread in, still I normally have difficulty getting the bolts into the diff, you can't get sockets on as the bush bolts interfere and the Al brackets get corroded badly to the steel cased bush due to the voltage difference between the metals. Designers and companies learn these things on the job.

Having worked at a number of makes/models of car over the years, I would say the 300's are one of the easier ones.

[Evoman]

Ride_on, when I mentioned assembly I meant in production. In this particular example welding a nut in would add alot of time and another more costly process. Breaking two "design for assembly rules" just covered it in uni.

[volvodspec]

it's all about taking time off the assembly line, that's how you can build cars fast; CVT and manual gearboxes were made off the production line, a simple 4-pin jig that resembles the mounting points under the car holds the brace bars in place; gearbox is thrown on it and bolted down; gear linkages mounted and job done. the same story for the CVT, but this also got it's belts on and was balanced; ready to go plug & play under the car.

so in assembly reality, a captive nut won't add speed as the bars are painted so you'll first need to clean the thread in the nut before you can bolt the gearbox to it. as these M8 nuts are locknuts you need to secure the bolts in another way; loctite for example. also not fun for maintenance
next downside is that you make a connection from steel to aluminium; corrosion might be a problem later on and if the thread in the captive nut is raped fixing it again properly is a bit more work as to simply getting a new nut+bolt

[mat_91]

captive nuts are a ball ache im glad they didnt use them
as 20years down the line when we come to undo them they just break the welds and spin at least a nut and bolt you could cut off

[Ride_on]

Yes I was aware you where talking about production, I am also an Engineer from a production background with a few more years experience than you. I'm glad you covered in uni, I hope you do as good a job as Volvo did when you start designing things. In work my job for many years was to assess designs for production, modify them, ramp them up to mass production, sort quality issues, make them cheaper etc (VHS video recorders so lots of disciplines).

Anyway you are talking about a 30+ year old design, Volvo was concentrating on safety and longevity then, while Ford was doing captive nuts. I've noticed my GFs 2003 Laguna has alot of captive nuts/threads, I'm sure its more efficient to build than the 300, but I'm also sure it is not as reliable.

effort in = quality out, you can never have a perfect design, stop slagging of Volvo on a Volvo forum, especially on a rather pedantic point!

Incidentally my first 345, on replacing the front cross member a captive thread tube in chassis leg let go, I had to cut it open to sort it out. This was on a 6/7 year old 1980 car.

..Students

[Evoman]

Ride_on, oh cool! Its obvoisuly a little different to the real world than in the perfect world of academia. That was my take, I wasnt sure if you fully understood what I meant, but you did lol. It will be interesting going into industry and learning real engineering