gearbox shot peening

[jdearden]

i am going to have a lsd and have gearbox refurbed over the winter along with new clutch. i have hear about shot peeing. is it nessasery as it seem very expensive to do this on top of everything else. what does it do and will it be fine without doing it. whats the best way to get it out cut chassee or take engine out. will be doing this myself with the help of friends. cheers for your help again in advance.

[m54321]

I am not an expert on this area but I not heard of peole doing this to the clutch assembly. Shot peening is taking small metal or ceramic beads and shooting them at high velcoity at metal this does two items. By shooting these items the metal surface is worked (hardened) this makes the surface harder but more brittle. It also rounds of edges and creates a high gloss finish but not necessary a very smooth finish. to the eye to surface looks and feels smooth but under a microscope the surface is a bunch of small indents. It is useful in items that needs to be smooth and resist heat (intake manifold.

Instead of spending that money I would spend the money on more exotic materials for the clutch.

That is my thought on the idea - would really like to hear other peoples thoughts.

[Mike Tuckwood]

m54321 said:

I am not an expert on this area but I not heard of peole doing this to the clutch assembly. Shot peening is taking small metal or ceramic beads and shooting them at high velcoity at metal this does two items. By shooting these items the metal surface is worked (hardened) this makes the surface harder but more brittle. It also rounds of edges and creates a high gloss finish but not necessary a very smooth finish. to the eye to surface looks and feels smooth but under a microscope the surface is a bunch of small indents. It is useful in items that needs to be smooth and resist heat (intake manifold.

Instead of spending that money I would spend the money on more exotic materials for the clutch.

That is my thought on the idea - would really like to hear other peoples thoughts.

I share very similar overall concerns as to the true benefit of this particular process.


Mike.

[TuxMan]

Shot peening is only done to the gears not the clutch , its supposed to make them stronger and the gear change better .

Alot depends on what sort of power you are running through the box ,i,m at the moment stripping out my engine ready for box removal ,planning to upgrade power to 420bhp with 400lb torque so the box is going to get the full treatment including oil cooler fittings as well . diff seems to be the main weekness on a 5speed box but it makes sense to do as much to the box while it is all out !!!

[JLSELAN]

There is a decent write-up here:
http://en.wikipedia.org/wiki/Shot_peening

Shot peening is used primarily as a mechanical stress relief procedure, and it can noticeable reduce the tendency for a material to crack/fail under repeated loading. It will have no effect on the thermal properties of the base material and only minor effects on surface hardness.

[jdearden]

i was going to replace clutch. i no you cant shot peen the clutch. was trying to work out if it was worth the extra 500 quid to shot peen it the gear box. i will fit a lsd aswell. whats the best clutch to fit or is there not really much choice apart from standard

[Adrian W]

non shot peened gear clusters break in Nobles, shot peened ones don't, of course it's your choice

[m54321]

I stand corrected on shot peening. That is an excellent summary on shot peening. Thanks for the info. I think that the article shows that shot peening is used on metals that have internal stress built up (welds or grinded metal) to get the internal stress out. That is why it is used on manifolds after a manifold has been grinded and or a pipe has been welded together. When those parts are used and the heat from the engine is exposed to the part the heat gets concentrated to the areas where there is internal stress. That is why the weld normally does not break but the metal immedaitely adjacent to the weld. Shoot peening helps allow the heat to be more uniformally distributed.

As the article points out unstressed metal sheet metal that is shot peened will bend (stretch) easier. The gears should not have interanl stress built up inside the metal so I do not see the need for shot peening

If I were to do anything to the gear (metal) I would look to get them cryogenic treated. This is a proven technology to add life to metal parts.

My first option on spending money would be to change the material to a stronger lighterweight material.

[YellowShed]

m54321 said:

As the article points out unstressed metal sheet metal that is shot peened will bend (stretch) easier. The gears should not have interanl stress built up inside the metal so I do not see the need for shot peening

If I were to do anything to the gear (metal) I would look to get them cryogenic treated. This is a proven technology to add life to metal parts.

My first option on spending money would be to change the material to a stronger lighterweight material.

It's way way more expensive to have a bespoke gear set cut!! And cut should give you a clue that the gears have been machined and therefore will have internal stresses and surface defects which shot peening is effective for - you don't want a small surface crack near the root of a tooth spreading and causing the whole tooth to break off. Also, one claim I have heard is that the shot peened surface gives a better surface for the oil to stick to - those tiny little dents allow the oil to pocket and survive the tremendous pressure in tooth mesh which means metal-to-metal contact is less likely.

I have also heard good things about deep cryogenic treatment and that may provide better value for money. Don't know of anyone whos actually tried it on a Noble gearbox yet, and as Adrian says, his, Ash's old car and Richards car all have had the gearbox done with no issues. Admittedly his and Richards have the gearbox cooling mod too and daddysumo's car also has cooling on it.

YellowShed

[JLSELAN]

Another point that may not be obvious is that shot peening is most effective when it is applied to newly machined parts, and the cost may not be justified for a used gearset that possibly has already started to develop cracks in critical areas. Simply put, shot peening is not a repair procedure.

[daddysumo]

JLSELAN said:

Another point that may not be obvious is that shot peening is most effective when it is applied to newly machined parts, and the cost may not be justified for a used gearset that possibly has already started to develop cracks in critical areas. Simply put, shot peening is not a repair procedure.

When I had my gearbox shot peened, CTS stated that its only worth doing on very low mileage units which agrees with the above statement.
I have a gearbox from my other car (Evo 6 TME) which is stripped at the mo and being cryogenically treated as it had covered 50k so shot peening was not a solution, we will see if increases the strength in the next few weeks as it will see around 550bhp and 500 ftlb through 4wheel drive, with anti lag launches which quickly destroys the standard ones.
Will report back !!

[TuxMan]

interesting stuff , again makes me wonder if it needs to be done as my box has done 340000 miles ....will have to contact gearbox man and ask .

[Gadgeroonie]

the Gearboxman has been involved in motorsport and strengthening gearboxes for a very long time

he is a very technical chap and strives to do the best he can rather than just make money

i have previously broken 6 gearboxes (another car) till i met the gearbox man, his box has lasted and taken hp and abuse the others were not capable of

i think the shot peening is a bargain if you look at the cost it will save you in the long run

[RobP]

TuxMan said:

interesting stuff , again makes me wonder if it needs to be done as my box has done 340000 miles ....will have to contact gearbox man and ask .

I think he'd need to have a look at the state of the box first. My gearbox was relatively high mileage (31K miles) when diff bearing gave up the ghost after 2 days at Spa. However, when he took the gearbox apart the actual gear clusters themselves were found to be in very good nick and so G/boxMan was happy to proceed with strengthening/shot-peening etc.

[jdearden]

Lots of different views. My car has covered 30k. I'm only refurbing the box and doing clutch as fitting an LSD. And might As well do other bits while got car in pieces. I thought better to fix befor they break. I think I will talk to gearbox man see what he says. He has quoted mr for all work. But shot peening seems exspensive.

[ThatPhilBrettGuy]

daddysumo said:

I have a gearbox from my other car (Evo 6 TME) which is stripped at the mo and being cryogenically treated as it had covered 50k

I only got 11k out of my EVO6 gearbox

[Gadgeroonie]

crikey - didn't have you down as an Evo owner

have you still got it

[The devil]

TuxMan said:

interesting stuff , again makes me wonder if it needs to be done as my box has done 340000 miles ....will have to contact gearbox man and ask .

Surely you meant 34000 Simon. Bragging again

[mr.man]

Just to fill in a few gaps that may be of interest. The majority of gears for automotive use are manufactured from an alloy case hardening steel,(EN36 or EN39). This will usually be in the form of a "black bar" i.e. hot rolled steel which will be free of stresses. The gear will undergo lathe work,drilling for oil holes,any milling reqd,splining if reqd,then gear cut. This machined component will be free of stresses. Heat treatment will consist of carburising,refining,re-heating and then quenching in oil. Tempering now takes place to relieve brittleness and ensure the gear is not too hard. For perfect running the involute gear form is now ground to exact dimensions for near silent meshing when in use. In normal use these gears last a life time.

However, due to the physical size of these gears and the constraints of the size of the gearbox experience has shown that they may break under the torque developed by a Noble in full power.

According to my metallurgist shot peening has the effect of compressing the grains on the surface of the steel giving the effect of a slighlty work hardened surface for improved wear resistance and also has the important effect of closing any microscopic flaws that could lead to cracks forming.

[ThatPhilBrettGuy]

Gadgeroonie said:

crikey - didn't have you down as an Evo owner

have you still got it

It went when I got the Noble. Great car though but with a stupidly small fuel tank.