15 replies to this topic

[SteveyM]

Hi all
I’m tempted by titanium bolts for the rear subframe trunnions to reduce the rust issues in the future.

However I’m aware that titanium isn’t as strong as the correct steel bolts - does anyone use titanium bolts for subframe fixings or is it better to just use steel and try to protect them as much as possible?

Thanks,

Steve

[sonikk4]

Hi Steve,

 

just done a quick check up on Titanium bolts and you need to make sure of several things. One is the grade and in the EU, it should be grade 6Al-4V.

The next is the class, so a range of Class 8.8 and Class 10.9.

 

Now as well as clamping force at the trunions there are several load factors to consider. The front trunions have a lot of shear loads, whereas the rear ones have a combination of both compression and shear loads.

 

These bolts need to be able to cover both so this is where the class range plays a major part. Now Titanium itself is quite brittle so the grade is very important as well.

 

Would you be buying these from Titan Classics by chance??? If so read their FAQ's.

 

Now would i use them, the answer would be no. Unless you are going to race the car where weight is everything then in a day to day car its expensive and pretty pointless. If you are worried about corrosion on standard bolts, then when you assmeble the bolts use a good quality copper slip grease.

 

We use Titanium bolts etc in everyday use on Civil Large Passenger Aircraft but these are designed with weight and strength in mind. If we change from one type of fastener to another i have to consult the relevant Structural Repair Manual where it will tell me whether i can use Titanium instead of steel etc. Even then there are still restrictions on where they can be used.

 

I know materials have come on in leaps and bounds since the mini was first designed, so far superior to what our little cars are built from and with. BUT you still need to be careful about the application.

[Tomm]

I just got the laptop out to reply and the above reply that has just been posted sums up in far greater detail what i was going to say, so thanks to Sonikk for that. 

 

Something else to be made aware of is that the cross contamination of different materials can lead to all sorts of different problems. It is important to understand that there are several different types of corrosion including galvanic corrosion, concentration-cell corrosion, stress corrosion, fretting corrosion, pitting, and oxidation. The most common form of corrosion is rust (oxidation) associated with steel structures and fasteners, although the effects of corrosive attack can be seen in many other structural materials. Obviously the application of the fixtures and the environments in which they are used plays a part. With this in mind I use an "Anti Seize" product to prevent the furring up and seizing of fasteners and fixings. We have found that Copper slip in some applications can speed up the corrosion process and I have opted for a product from Rocol, simply their "Anti-seize" which I have been very happy with. 

 

It may be worth considering something similar for your mini. Replacing all bolts with titanium items will be far more expensive, and there is always the possibility of selecting an inferior standard bolt. There is a weight saving to be had with titanium items and over on the Turbo-Mini forum there are a lot of guys who are changing over to titanium fixings with great results. 

 

I don't for a second claim to "know it all" about this subject, I can only contribute what I have learnt in an attempt to help. 

 

All the best with your car. 

[sonikk4]

I just got the laptop out to reply and the above reply that has just been posted sums up in far greater detail what i was going to say, so thanks to Sonikk for that. 

 

Something else to be made aware of is that the cross contamination of different materials can lead to all sorts of different problems. It is important to understand that there are several different types of corrosion including galvanic corrosion, concentration-cell corrosion, stress corrosion, fretting corrosion, pitting, and oxidation. The most common form of corrosion is rust (oxidation) associated with steel structures and fasteners, although the effects of corrosive attack can be seen in many other structural materials. Obviously the application of the fixtures and the environments in which they are used plays a part. With this in mind I use an "Anti Seize" product to prevent the furring up and seizing of fasteners and fixings. We have found that Copper slip in some applications can speed up the corrosion process and I have opted for a product from Rocol, simply their "Anti-seize" which I have been very happy with. 

 

It may be worth considering something similar for your mini. Replacing all bolts with titanium items will be far more expensive, and there is always the possibility of selecting an inferior standard bolt. There is a weight saving to be had with titanium items and over on the Turbo-Mini forum there are a lot of guys who are changing over to titanium fixings with great results. 

 

I don't for a second claim to "know it all" about this subject, I can only contribute what I have learnt in an attempt to help. 

 

All the best with your car. 

 

Another product you can use is a Nickel based anti seize. Something we use a lot especially on engines where heat is a major concern. Never had corrsion issues with Copper Slip personally but worth baring in mind.

 

I think its all food for thought and where you want to go with the car, BUT if you have any doubt about the quality of the bolts then steer clear. I have got a couple of stainless steel bolts on my car but its only on the Minivation hinge mounts. Everywhere else it will be steel bolts. 

[Tomm]

I wont quote you Sonikk as we will end up with a huge quote reply, however the research we have done with copperslip has been with stainless steel items based in a marine setting, so it may work absoloutley fine in an automotive capacity with no negative effects and I am sure It has done for years. I know Copper slip is a far signt cheaper than Rocol. Out of interest, as a potential alternative what nickel based product are you using? 

 

I have a few A4 stainless fixings on my car, not many though. I work with a chap who against much advice built a Locost style car and built all suspension arms out of 316l Stainless tube, fitted with stainless fixings to a mild chassis. As you would expect he had no end of problems. 

 

As an unrelated note I read your whole build thread the other day, very impressive. 

[SteveyM]

Thanks for the info both. Had hoped they were the answer but suspected there was a catch.

I’m building up a new heritage shell so desperate to protect it from the rust monster for as long as possible.

[sonikk4]

I wont quote you Sonikk as we will end up with a huge quote reply, however the research we have done with copperslip has been with stainless steel items based in a marine setting, so it may work absoloutley fine in an automotive capacity with no negative effects and I am sure It has done for years. I know Copper slip is a far signt cheaper than Rocol. Out of interest, as a potential alternative what nickel based product are you using? 

 

I have a few A4 stainless fixings on my car, not many though. I work with a chap who against much advice built a Locost style car and built all suspension arms out of 316l Stainless tube, fitted with stainless fixings to a mild chassis. As you would expect he had no end of problems. 

 

As an unrelated note I read your whole build thread the other day, very impressive. 

 

The product in question is Bostik Never.Seez pure Nickle Special. Very high temp up to 2400F. We use this especially on combustion chamber Boroscope ports.

[Magneto]

The 8.8 and 10.9 grades are for metric fasteners, he needs grade 8 for suspension bolts as they are "imperial" sizes.....I just use chassis grease on the bolts, works just fine considering very few Minis get driven more than a few hundred miles a year today. Mine are one exception - I probably do 5000-7500 miles a year in mine,  but I'm in the states......many of the events I go to are 1500 miles away or more.

[DeadSquare]

It is not exactly "rocket science", more like "brain surgery", cut the screws down to the correct length. If they are too long, the protruding end gets rusty and won't retract.

 

I make up a simple gauge, of a bit of wire bent into a hook on one end, poked through a close fitting hole in a suitable piece of wood.

 

Load the hook with the object (in this case, the trunnion and spring washer ) and insert the hook in the captive nut;   hook it and close up the piece of wood.

 

Very carefully unhook and unload it and "Bob's your Uncle" you know how far from the head of the bolt to cut.

 

 

 

Having applied "whatever" grease, wrap PTFE tape round the thread twice, and screw it in.

[Spider]

Does Titanium react with other metals like Stainless does ?

[sonikk4]

Does Titanium react with other metals like Stainless does ?

 

Lots of information out there with regards to Galvanic corrosion and Titanium. Yes there is some reaction but it would appear to be light. However a lot of Titanium fasteners come with a Anodic coating which when left intact does help to prevent Galvanic corrsosion.

 

Also we tend to use an Anti Corrosion paste when assembling Titanium fasteners (removable) or an Anti corrosion type sealant (PS 870) with Hi loks.

 

Something else to bear in mind with Titanium is Hydrogen Embrittlement which can be caused by certain cleaning products / solvents etc. And yes Titanium itself can corrode but its something we rarely see.

[Ethel]

It conducts electricity so galvanic..... Neil did it again 

 

How about just adding the bolts to your service schedule? Remove check and/or replace annually.

[DeadSquare]

Thirty something years ago. "THEY"  advocated Titanium bolts to hold the blades on helicopters.

 

Because Titanium was novel, these replacement bolts required frequent inspection  (Which in its self, created another problem)

 

In due course the inspection interval became longer and longer until the bolts were permitted to remain undisturbed between overhauls, at which time it was found that they had become so seized that the whole rotor-head had to be removed and manhandled under a hydraulic press.

 

"If it ain't bust..............don't fix it"

[Spider]

Many thanks Neil. Not a material I know much about nor had any experience with, but certainly more wised up to it now.

 

Cheers.

[sonikk4]

Titanium is a swine to work with having done many repairs over the years.

 

It was used a lot on Lockheed 1011 Tristars as tear strips. These were designed to help prevent cracks from spreading between frames and were redux bonded in place. However over time the Redux disbonded meaning we would have to rivet the damn things in place. The material was only 0.016 in thickness and was like a razor blade. Drilling it was a pain and so we would use cobalt drill bits.

 

Titanium Hi Loks are a personal favourite of mine as are Titanium bolts / screws. I'm normally one of the go to guys for drilling these bloody things out when people snap them / butcher the heads etc. I have lost count of the hundreds i have removed over the years. Also having a working knowledge of being able to decipher the SRM of not only Boeing but Airbus when it comes to using alternative fasteners.. 

 

I have used Titanium plate for various skin repairs over the years along with Stainless Steel and both are a pain.