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standard anodizing will add roughly 1/2 to 1 mil of surface to any aluminum part. the anodizing, depending on how long it's left in the electrolyte bath, will be between 1 and 2 mils. So the oxidized layer will extend outward, and inward by about the same amount.

this layer is porous, and can be dyed. then a hot bath will seal the dye and the pores of the oxidized layer, leaving you with a hard colored surface.

HARD anodizing is the same process, with colder electrolyte bath and higher current density. this layer is twice as thick or more, and due to the color of the oxidation layer, it not readily dyeable because it forms a dark gray/green, brown or black depending on the alloy. About the only color you can do is black, since it is darker than everything else.

Some alloys can be anodized and then colored, and others will form a dark oxidation layer than can't be color matched.

A nice, simple FAQ on anodizing: http://www.globalmetalfinishing.com/content.aspx?ContentID=1355

I put my Optima final pinions on a balance here at work (all sans set screw):

Kyosho Stock Aluminum: 5.33 g

Kyosho Hard (hard anodized aluminum): 5.15 g

Thorp Steel: 15.02 g

Here are two pinions I have. The one on the left is from a stock Optima parts car. The one on the right is from a stock Optima that had the belt drive and other add-ons (so a hard final pinion would be more possible). They seem different looking to me, is the one on the right a hard final pinion? If not, how do you tell?

Thanks.

They're both stock aluminum. Hard final pinions are the color of AE hard anodized shocks (gray/olive greenish) and they have a single groove machined in on the non-tooth end (ignore the two shallow scuffs from the chain). See the attached pic (hard pinion is on the right).

Thanks, that single groove tip clears it up.

ROH73 wrote:I put my Optima final pinions on a balance here at work (all sans set screw):

Kyosho Stock Aluminum: 5.33 g

Kyosho Hard (hard anodized aluminum): 5.15 g

Thorp Steel: 15.02 g

My measurements would be nearly identical. I weighed 2 stock alloy gears and both were around 5 grams. The unknown-brand gear I have weighed 15 grams, so it must be a Thorp Dirt Burners gear. I have another but I can't weigh it as it has a shaft stuck through it and it's damn near cemented on with the set screw, I can't remove it and I'd be worried about stripping it out.

It seems lighter than the Thorp one and has a groove whereas the Thorp doesn't, so I'm guessing gear #2 is the hard-anodized unit.

Yeah, it's probably the hard anodized version. Can you get the set screw out and do you have access to a press?

How hard would it be to machine some final pinions out of either a harder metal than aluminum, or out of plastic?

Not too hard, but probably costly. I'd personally rather go with jwscab's suggestion of http://www.amainhobbies.com/product_info.php/cPath/1_25_1466_663/products_id/115511/n/Robinson-Racing-Extra-Hard-Steel-5mm-Bore-8-Mod-Pinion-Gear-19T and use some spacers.

i dont know if this is old news but i just received 2 Dirt Burners "thorp" final pinions and noticed that they were heavier than the standard or stock aluminum pinion so i did the magnet test and yep they are metal , are these considered "hard" pinions?

Yes, they're steel and they're harder than the stock aluminum pinions, so they're considered "hard" final pinions.

I agree with ROH73. I've just installed a NIB OT-76 and it definitely has the single groove, the same colour as the one in his photo, and it is steel.

Speaking of new hard final pinions, I've pulled the original chain diffs and stock final pinion out of an old Optima. I've installed the new OT-76 pinion, a new W-0105 belt drive and Option House ball diffs (W-0107 at the rear, W-0108 at the front). I am still working in the build - it's not complete yet. The belt drive feels rough when I operate it by hand. Initially I thought that it was the belt drive pulley being installed too tight, but now I've worked out that it's because the final pinion to diff gear backlash is very tight. There's no apparent way to adjust it - the centre to centre distance is set by the position of the bores in the gearbox.

Is this normal? It seems odd. Do you guys know if it will just 'bed in' after some use or is there something that I can do?

Cheers!

Mike

ROH73 wrote:Not too hard, but probably costly. I'd personally rather go with jwscab's suggestion of http://www.amainhobbies.com/product_info.php/cPath/1_25_1466_663/products_id/115511/n/Robinson-Racing-Extra-Hard-Steel-5mm-Bore-8-Mod-Pinion-Gear-19T and use some spacers.

losiXXXman wrote:I may be wrong, but those 32p pinions with 5mm bores are what is used on the big 8th ebuggies. I would think they'd be tough enough for some Optima use, if they handle that kind of power and abuse.

I thought that was MY idea.

The ultima has the same gearbox, and I've heard that it's a little tight w/ new gears, but they'll wear in. I've not had the chance to do new gears in any of mine yet..