Hi I am currently designing an assembly which uses your 47.5idx50.3od carbon roll wrapped tube and i was wondering what tolerances i'd need to have on the housing to get a good fit.

Also if you could let me know what adhesive to use to join the tube to the housing that would be great.

Arron Howe,

Apex Designs Ltd, Bristol

The tolerances depend on your application. Also is the housing bonding to the inside of the tube or the outside? Roll wrapped tubes have tighter manufacturing tolerances on the inside diameter due to being manufactured on a mandrel.

In terms of adhesive, we would recommend either our ET500 Rigid 5min Epoxy Adhesive or our ET515 Semi Flexible 15min Epoxy Adhesive for your job. 

We recommend the ET515 Semi Flexible 15min Epoxy Adhesive where a higher level of flexural strength is needed such as in the case of assemblies subject to shock and vibration.

In all cases, remember to key the surfaces to be bonded, this is especially true with roll wrapped carbon tubes as a release agent is used to get them off the mandrel so you would struggle to get a bond unless you keyed the surface thus removing any release agents.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

We are bonding to the OD of the tube, as for the keying of surfaces is there anywhere you could point me, tutorials etc on how you'd generally do that?
Its just we've never used carbon fiber before and it's quite a precision job that is required.

Arron Howe,

Apex Designs Ltd, Bristol

Keying/roughing up the surface can be done with a rough grit sandpaper. You just need to ensure the dust is cleaned off afterwards.  The aim is to make a non-smooth surface to help the adhesive form a mechanical lock with the two materials.

There is really nothing complicated at that stage. The concept is exactly the same as keying a raw surface before painting.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Ah ok thanks ti thought you meant as in adding key ways.

Do we have to key the housing and the tube or just the tube? and is it ok just to bond the OD to the housing or do we need to bond to both diameters?

Arron Howe,

Apex Designs Ltd, Bristol

I've never used theses adhesives they are obviously excellent,also consider wet sanding I used to bond metal parts using epoxy.while its wet sand it into the metal using 120,this eats into the metal creating excellent secondary bonding if you where making your own adhesive ie microfibre,silica or other high density filler this is just thought it can get a little messy I have repaired railings over 3 years ago still and still strong.

You are best to key up both surfaces to be bonded.

You should be fine bonding just the o/d to the metal work.  In theory for some really high stress applications you might need an inner and outer bond but if that is the case, you will likely be looking at a stronger tube as the tube would break before the glue!

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Ok that's Great thanks. Also i still need to know what tolerance you'd recommend for this, what tolerance are your tubes manufactured to?

Arron Howe,

Apex Designs Ltd, Bristol

The outside diameter can vary by as much as 0.5mm dependant on tube size and wall thickness.

When you are talking of small gaps like 0.5-1mm then i wouldnt worry about the fitment coming loose. Any void will be filled with adhesive so you will have a solid joint.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks For all your help could you just confirm hat the tolerance is +0.5 or +-0.5mm.

Arron Howe,

Apex Designs Ltd, Bristol