M3 screws seperate

[Chrislong]

Hi Olivier,
Now thats hardcore

Fancy bagging up conversion kits prepped to be built this way? (as many of us, such as me, won't want to do this mod) Im guessing it'd need gearbox halves front and rear, all the purple blocks and the 12 screws?

How much?

[frogger]

Nice job! I'll have a conversion kit as well if there will be one

[glypo]

I have M4 screws in mine also. Sorry didn't see the post asking for photos before, I will sort some out later.

Northy, it is not possible for the mod to put more stress on the transmission housing, if anything it takes away stress.

It's not exactly a hard mod to do, although I will put a step-by-step guide in my follow up review soon to be finished.

[Northy]

It must put more stress into the gearbox sides....

G

[barnyard]

The gearbox sides have enough material in them (especially the front) the pivot blocks are more of an issue when drilled out.

I even know team drivers running the car with the front end modified

[Northy]

Who?

I must admit I had thought about it.

G

[glypo]

Originally Posted by Northy

It must put more stress into the gearbox sides....

G

How? It takes it away.

Just got in from work and I'm doing maths again already....

M3 = Nominal diameter 3 mm
M4 = Nominal diameter 4 mm

Stress = Force / Area

Therefore stress is inversely proportional to area.

Circumference = pi x d

M3 = 3.14 x 3 = 9.42 mm
M4 = 3.14 x 4 = 12.56 mm

Obviously this is a 33.3% increase in surface area, thus stress around the screw will drop by 33.3% also. So therefore the stress will be reduced on the housing with a bigger bolt.

[Oliv996]

Thanks Chris !!!!

I do not plan to produce a machined M4 and M3 screw set but if some of you want I could make an effort... I would prefer to let you drill and tap the require parts (gearbox halves, bloc pivots, spacers) 'cause it take a while and I have to do it for French guys who already ask me

Once I will do the job on french side, I will consider your demand Chris as my small contribution to Team Schumacher UK

Olivier

[Oliv996]

Originally Posted by glypo

How? It takes it away.

Just got in from work and I'm doing maths again already....

M3 = Nominal diameter 3 mm
M4 = Nominal diameter 4 mm

Stress = Force / Area

Therefore stress is inversely proportional to area.

Circumference = pi x d

M3 = 3.14 x 3 = 9.42 mm
M4 = 3.14 x 4 = 12.56 mm

Obviously this is a 33.3% increase in surface area, thus stress around the screw will drop by 33.3% also. So therefore the stress will be reduced on the housing with a bigger bolt.

The ration between M3 and M4 is quite still the same but you must consider the core diameter of the screw: 2.5 for M3 and 3.3 for M4

[glypo]

Originally Posted by Oliv996

The ration between M3 and M4 is quite still the same but you must consider the core diameter of the screw: 2.5 for M3 and 3.3 for M4

Originally Posted by glypo

M3 = Nominal diameter 3 mm
M4 = Nominal diameter 4 mm

The key is in detail. Never clever to correct someone without reading their post. I was clearly referring to the nominal diameter of the screw body.

[Oliv996]

oOps sorry Glypo, it was just my 2 cents on the topic....

BTW with your considerations above, I agree with you calculation

[Northy]

Ok, but if force x is put onto the purple wishbone pivot pin hangers, and is enough to bend the screws, if you put bigger screws in, and then apply force x again, isn't there more pain on the gearbox sides now as the screws don't bend to 'save' the gearbox sides?

G

[Chrislong]

i agree with you G, the force absorbed by screw bendages is transferred to another part. That could mean more broken wishbones, or bendages to the gearbox.

But also in theory the calculations make sense, but what is lost marginally is surface area of gearbox half by putting bigger holes in.

Personally, I can't see the gearboxes bendage-ing, so it'll be wishbones. But if running the mid-flex wishbones whats to say that we won't even bend m3 screws...

oh, there are just too many variables, and ive had too much wine to think about it.

[glypo]

Oh right, I see your logic now and why you say more stress.

For sure, as the screws bend, they will absorb some force. However the screws don't bend too much, and even so they do not break. A breakage releases loads of energy.

The small bend will absorb maybe 2-5% of the impact energy, the rest has to travel through the transmission housing as stress and strain. And once they are bent, the extend to which they can bend further is limited so the transmission housing then takes 100% of the impact.

So I think this mod adds no extra stress really, and saves hassle of bent screws. I will test it out next weekend at the MK GP, that track will no doubt test their strength. Nice and easy to do too, you only need two drill bits and a M4 tap

[glypo]

Originally Posted by Chrislong

But also in theory the calculations make sense, but what is lost marginally is surface area of gearbox half by putting bigger holes in.

Sorry for double post, you posted as I was replying. (I also have had a little to drink so replies seem to take longer with other distractions).

The hole cut makes no difference, as the gap is filled by the screw so there is no real strength loss in terms of that.

[bigred5765]

and a bigger leaver moment from the bigger screw, ie bigger bar easyer to bend,

[glypo]

Originally Posted by bigred5765

and a bigger leaver moment from the bigger screw, ie bigger bar easyer to bend,

Nope. Moment = force x perp. distance from pivot.

The M4 screws I have used (high tensile steel cap screws) are the same length as the standard M3's.

[glypo]

Forgot about this. Anyway, tonight when putting my medium flex wishbones for the MK Racing GP tomorrow I remembered and took a couple of snaps.

M4 high-tensile scew mod. Takes 20 mins max - and hopefully will solve the issue.

[ashleyb4]

Any chance you could maybe put a hing pin straight the way though?

A

[glypo]

I see where you are coming from, and yes and no is the answer.

There are two mount points, you could put a pin through the first mount point, but the diff is in the way for the second. There is no movement at that point though, so no need for a pin, and it won't add much strength over a screw of the same diameter.