Mag wheel fail - help !

Nattyboy

Getting there in terrms of building the new bike back up. However, put one of the discs on the mag front wheel, and two of the threads have stripped out of the bloody wheel..arrrrrrrrrrggghhh !!!

Easy to get fixed ?

Cheers
Nat

ducatipaddy

Helicoil ? If its done well it should be ok.
Drill out, tap, plug and re-drill tap original size.

There is a guy near you who does Magnesium wheel repairs, he might be able to TIG weld it
I will look for the address and get back to you.

EDIT

This is the guy i was thinking of, he's an ex Dymag guy.

http://tpcs-magnesium-refurbs.co.uk/contact-us.phpw

Might be worth a phone call.

Mr.R

1st choice would be a "Timesert", 2nd would be a "Helicoil" or a "Recoil" which's the Aussi made equivilent,
it's good kit and costs less. 😉
I'm not sure about Mag'? How the F'ck do you weld it without setting it alight?
But even the best aluminium only returns to 70% of it's original strength after welding and then heat treating...

Steve R

mikesps

Nat,

I bought a second hand Mag Marchesini front with several helicoiled bolt holes. The holes have not been treated, so it looks like they will continue to corrode.

I haven't fitted them yet as they have not been tested. Dymag would crack test them, but do not repair damaged threads.

I found these people who do weld magnesium. They seem happy to repair quite severely damaged wheels, but I haven't spoken to them yet about this repair.

http://www.alloywheelrepairs.net/index.htm

Mike

Lawson SP3

Mr.R wrote1st choice would be a "Timesert", 2nd would be a "Helicoil" or a "Recoil" which's the Aussi made equivilent, it's good kit and costs less. 😉 I'm not sure about Mag'? How the F'ck do you weld it without setting it alight? But even the best aluminium only returns to 70% of it's original strength after welding and then heat treating... Steve R

I'd agree with the Timesert since they are the smallest OD of all thread inserts (and generally the 'best' in most cases). If you need to repair again down the road there is enough material to accept a different insert type. When I was still race wrenching it went Timesert, Keensert, HeliCoil. I actually surprised the wheel wasn't done with inserts from new. As much as aluminum doesn't like repeated installation/removal of threaded items, magnesium really doesn't like it. Installed/replaced inserts more times than I care to remember where the underwing attached to the gearbox case on the Indycars. Lots of tension from the low pressure created, even more vibration, and the expansion/contraction of the case material itself = lots of inserts coming adrift.

As for the welding, first off, everything needs oxygen to burn and the shielding gas keeps the oxygen away. Also, magnesium transfers heat so fast that it requires lots of surface area to ignite. I've welded up cracks in magnesium gearbox cases and even rebuilt broken off mounts by welding up and cutting/grinding/drilling. The hardest part is actually keeping the whole thing hot while welding to avoid uneven cooling and thus cracking. Usually have someone running an oxygen/acetylene torch keeping the heat in.

Foggy 888

Having used both Timserts and Helicoils, I prefer Helicoils. You have to machine a hole with a step for the Timesert, and this doens't look or work as well as the helicoil. I have never had a helicoil come out, but have had many timesert come out. Dymag, Ferrari, Spondon and other manufacturers use helicoils as standard in there products. The od of the hole is actually less for a helicoil then a timesert.

851 tricolore

on the Marchessinis that I sold recently- all the threaded holes had inserts similar to Helicoils- I thought it must be original and standard practice.
Would certainly be kinder on the magnesium, and stronger?
Ian

Lawson SP3

Foggy 888 wroteHaving used both Timserts and Helicoils, I prefer Helicoils. You have to machine a hole with a step for the Timesert, and this doens't look or work as well as the helicoil. I have never had a helicoil come out, but have had many timesert come out. Dymag, Ferrari, Spondon and other manufacturers use helicoils as standard in there products. The OD of the hole is actually less for a helicoil then a timesert.

I looked up the info and it seems I had it a bit jumbled (has been a long time!). Keenserts are the largest OD when comparing similar types (lightweight, std. duty, heavy duty, etc.). It is basically a wash with the other two.

Mr.R

It's true that a step needs to be cut to fit a Timesert but...
There's a tool provided for this job in the kit that can be used by hand using the same tool as the one that holds the thread tap.
If fitted correctly the timeserts are almost bomb proof, I fit them using the tool that swages* them out but also use Loctite with them, I've NEVER had one come out again when doing this.
I can't say the same about Helicoils or Recoils.

*a Timesert is swaged out to make it a tight fit, a Helicoil or Recoil is "only" held in place by the spring tension of the coil.

Steve R

Jasper

I would go for the helicoil. If you use a thread retainer as well,this will give you a barrier against corrosion.

I have your brake bits.How many?

Nattyboy

Thanks lads! Feel a lot better now! I might ride it steadily down to louigis to get done with just the two bolts missing. Jasper - 2 please mate - and not sure if you git my text earlier but send me your email as I want to run a couple of things past you !

guy851

Thread retainer

Agreed Jasper but make sure you use the right compound as they are different for stainless and titanium into magnesium

I was recommended Loctite 2701 for Ti disc bolts into mag wheels

guy851

I quite like the inserts with the "tophat" step myself especially if repairing a buggered sparkplug thread

Jasper wroteI would go for the helicoil. If you use a thread retainer as well,this will give you a barrier against corrosion. I have your brake bits.How many?

final_edition

I've repaired a 916 front wheel with keensert inserts and found that a M8 screw yielded before the insert failed. At ~ 100NM

There was plenty of meat around the od. It pays to get them dead perpendicular to the mounting face.

http://www.specialty-fasteners.co.uk/updoc/Complete_Keensert_Catalogue_June_2008_1_1.pdf

Mr.R

I've used Keen serts to rescue Bevel barrel studs but I'm not sure if I'd use them in the Mag' wheel disc bolt situation??
I'll stick with the Timesert solution fitted with Loctite to form a chemical barrier between the sert and the Mag'.

Steve R

Lawson SP3

Mr.R wroteI've used Keen serts to rescue Bevel barrel studs but I'm not sure if I'd use them in the Mag' wheel disc bolt situation?? I'll stick with the Timesert solution fitted with Loctite to form a chemical barrier between the sert and the Mag'. Steve R

Your concern should be the other way round. The rotor bolts are in shear and the barrel studs are in pure tension. The (any) insert is more likely to fail in tension than shear because the insert is relying on a minute amount of base material surrounding it for its installed strength.