Frozen bobbins

[nmauduit]

After working in the Aero Space Industry for 20 Years as a QC Engineer i can assure you Helicoils present no problem
Alan

I thought we were talking about Lotus bobbins ...

[alan.barker]

We certainly are but what is good in the Aero Space Industry is easily good enough for a Lotus.
Wouldn't you think.
As you like it's your Lotus and your choice no problem.
Just looking for the easiest way to fix the problem.
There's more than one way to skin a Cat.
Amicalement Alan

[Donels]

Agreed. Just drilled all the bobbins in the body floor For chassis fitment and fitted helicoils. Much stronger and about 5 - 10 minutes per bobbin.

[nmauduit]

We certainly are but what is good in the Aero Space Industry is easily good enough for a Lotus.
Wouldn't you think.
As you like it's your Lotus and your choice no problem.
Just looking for the easiest way to fix the problem.
There's more than one way to skin a Cat.
Amicalement Alan

I'm not sure the material used in Lotus bobbins is often used for structural fastening in aerospace applications : I suspect the softness of the alloy may lead to the shearing force to be applied preferentially to the outside thread, with the risk of the corresponding coil moving around and eventually making its way out, etc... while this outside coil would be attached by the insert material, arguably stronger, if using a solid insert. I used coils myself quite often, but only when I can make sure the receiving material is solid and structurally homogeneous (the coil holding into it when being pushed from the inside by the fastener)

[Emma-Knight]

Try to save the Bobbin. Hot and cold
cycles could do the job. Just heat the bolt, let the heat transfer into the bobbin and then give some Blue ice spray just on the bolt. Repeat several times. The bobbin it self will be ok. It’s the powdery MAZAK deposits and the steel rust that needs to crack apart. Also rusted bolt end protruding on the other bobbin side might need treatment.
This is how I get 30 year old brake lines separated on daily drivers
(Just saw it’s the chassis bolts - the heads might be stuck to the chassis, not only the bobbins. )

Anna

[alan.barker]

Agreed. Just drilled all the bobbins in the body floor For chassis fitment and fitted helicoils. Much stronger and about 5 - 10 minutes per bobbin.

+1
Alan

[jono]

..looks like helicoils get the nod then

Thanks for the comments

Cheers

Jon

[miked]

Hi Jon,

I have done helicoils on the bobbins in the past and should still have the kit under the bench.

Cheers Mike

[jono]

Cheers Mike, will bear that in mind as I don't have any and have never done them before.

Meantime however a bit of good news - spent the afternoon on the project yesterday and manged to remove all bolts in the driver foot well including chassis except one seat bolt which sheared.

It would seem that patience eventually paid off as I've been 'feeding' them with GT85 for a few days now and it eventually did it's stuff.

Cheers

Jon

[TBG]

As I stated earlier I just drilled through and popped in stainless steel bolts and nuts with big penny washers. This caused a bit of a discussion about mixing stainless with aluminium. I get that - but what I don't get is fitting Helicoils as an alternative as they are made of stainless steel!! Enlighten me please.

[nmauduit]

As I stated earlier I just drilled through and popped in stainless steel bolts and nuts with big penny washers. This caused a bit of a discussion about mixing stainless with aluminium. I get that - but what I don't get is fitting Helicoils as an alternative as they are made of stainless steel!! Enlighten me please.

Helicoil.jpg

in this specific case if the helicoils do hold well over time it would not be an issue, as they are not supposed to be taken out (actually getting the coils to weld themselves to the bobbin would even be favorable, if that takes places as much considering the alloy the bobbins are made of)

[alan.barker]

"Enlighten me please. "
Sure same idea as original but stronger.
Won't rust.
Keeps original size Dia Screws.
Don't need someone on opposite side with Spanner on Nut while you tighten from below.
Lighter
How's that for a starters
As you like and it's your choice and it's nice to know there is different ways.
But please stay with Imperial Screws and don't mix with Metric
Alan

[TBG]

Yes - but won't the helicoils have the same galvanic issues as my bolts?

[alan.barker]

Yes,
but that means they won't move =no problem.
Alan

[TBG]

Bit like the bolts then!!