Bad teeth

This is an drawing of what I was explaining to Dereck regarding his gear post. took a while to work out the photo post and still not correct but you should get the point about poor tooth design. apologies for the photo post. I struggle with posting photos. got a 6 year old computer running XP.

Left side tooth is what the standard AMC14T 1st gear pinion looks like.. the undercut is very evident. poor engineering. on the right is a gear with a modified tooth profile. this gear has only 13 teeth so the ratio has changed a small amount, 14/28 original, 13/28 modified.

the modified profile has at least twice the life and about 20% increase in power capacity. far more durable. MAY pit slightly in the tooth bottom (dedendum) but not enough to be unsafe or unservicable. at least twice the life and transmits more power without damage..

this modified 13 T gear will fit straight in to the existing pair. no need for any changes on the 28T gear at all. 13T is simply cut instead of 14T. same outside diameter on 13T and 14T.

There are lots of other ways to get better tooth profiles. However this usually involves changes to the 2 gears of a pair and may include non standard centre distances. however the ratios may stay the same using other methods.

Looking at photos of the TTI box, I reckon they have done something similar to their tooth design. their teeth look stronger.
at a guess I reckon TTI run 22 1/2 degrees pressure where AMC run a nominal 20 degree pressure angle. 22 1/2 are stronger and carry more power. runs not quite so smooth and quiet but on a motorcycle you will not notice. too much other noise going on..

Anyway my point is that a lot of troubles with these gear teeth can be mitigated by design modifications. especially when speed and power are increased.

The gearbox shell and shafts are another story and are not considered here. the point of the post is more durable stronger teeth only. The TTI box is a fine example of good design and engineering. Do TTI recommend ATF or EP gear oil and what viscosity ?.


Contrary views and corrections welcomed Aussie Bradley

Take a look at the norton sleeve gear on Ebay, Triumphtwinspares..biggest load of shite! the teeth are grit blasted! Another cheap Indian part?
What the hell are these people doing, peddling rubbish!

This is interesting because I just recently read a mid seventies article regarding the "new five speed gear cluster for Vincents" on offer by Rod Quaife, who, aside from building great transmissions for all sorts of race cars, is a motorcycle enthusiast.
I believe Rod had a Vincent or two and decided he could build a better shifting trans for the Vincent, which he did and still does.
In the article, Rod is quoted as saying he needs someone to step up and make a minimum order of twenty five gearsets in order to produce the first of these kits. At the exorbitant price of £100, it was ten years before another Vincent enthusiast, John Surtees, stepped forward to order twenty five of the kits. Today they are still available from Surtees Sport Power, in fact that is the only retail source for the Quaife 5 speed kit for Vincents.
Self appointed moderator Needing might ask how this is all connected to Commandos, particularly HIS Commando.
Quaife also makes gear kits and complete gearboxes for Commandos. I am guessing that the gear tooth geometry of these kits is at least as well executed as the tooth geometry of these mid seventies Quaife Vincent sets (unchanged today, other than ratios)
In 1975 Rod Quaife was questioned about the ability of the slender gears in the five speed (half the width of stock Vin gears) to handle the mighty Vincent, which was said to have it's original four speed transmission designed for 100 hp. Rod responded that much had been learned about gear tooth geometry in the preceding twenty years. Due to great improvements in tooth design, the slender gears in the 5 speed cluster were good for not 100 but fully 180 HP!

Glen

Bruce's recommendation for lube on my TTI box :

Use 330ml of Castrol Syntrax 75W/90 or equavalent oil. Do not use a shock proof oil.

Hm Bruce's TTI instructions for Peel in 2014 was Redline gear oil 75w140 but looks like Amsoil is better for her staying in lower gears a long hard time.
http://www.lastgreatroadtrip.com/wp-con ... arison.pdf

hobot said:

Hm Bruce's TTI instructions for Peel in 2014 was Redline gear oil 75w140 but looks like Amsoil is better for her staying in lower gears a long hard time.
http://www.lastgreatroadtrip.com/wp-con ... arison.pdf

Click to expand...

I'd be inclined to go with TTI's recommendations versus the results that Amsoil conducted.

Definitely agree that one certainly couldn't go wrong with the Amsoil product. I've used many of their products for many, many years. Both when they sponsored my racing efforts and when they did not.

I am not disputing the results or validity of those test nor the value of Amsoil products, only suggesting that tests are meaningless unless put into proper perspective, just like statistics, surveys, etc. I currently have in my garage oil products from Amsoil, Elf, Mobil 1, Motul, Redline, Rotella (Shell), Spectro and have a specific purpose for each one based on the requirements of a specific application and the specific vehicle. Don't get me wrong, I'm not an engineer in this or any other field (suppose that's a blessing and a curse). I'm just someone who perhapsthinks too much and is opinionated (based on reading qualified materials and pertinent practical experience and applying proper critical thinking).

I've never felt that because a 1/4" drive ratchet will fail when used to apply 80 lbs/ft it wasn't useful for applying 15 lbs/ft. This is where taking the Amsoil results on their face value can create problems. The best gear oil on the planet is a waste on the differential of my snow blower but I just put 4oz of 75w-140 synthetic ($28/L) in to it last night as a makeshift fix to prolong it's life to deal with today's snow fall, and it lived just long enough to do what was needed, dying a noble death at the very end of the job. That was needed to handle the internal temps of the failing diff. Had everything been in reasonably good condition most any old 90w dino lube would have worked fine. ;-)

If you look at where Redline failed it was in the Brookfield test and the foam test. In the Brookfield test it failed the 75w minimum but passed for the 80w test. Therefore, if the Redline is used in an application that requires a minimum of 80w or more, it will be fine. The fact that it won't pass the 75w minimum is of no consequence. The other test that it failed was the "Foam New Oil" test. There it failed by a noticeable amount, but only in Sequence II which (I believe, but others likely know) is performed at a higher temperature (200F) than the TTI gearbox lub runs at. If that is the case, than the Redline should perform properly in that application.

I've used all the lubricants in my garage in racing applications in the past without issue, and think highly of them.

Where a manufacturer recommends a particular lubricant, I either use that lubricant or discuss it with them directly, as they:
a) unlike Amsoil don't have a vested interest in which lubricant I use, only that it work properly with their product, and,
b) have more experience/exposure to the performance/reliability/failures/issues/etc., of the product than anyone else

YMMV, but for the specific application noted, I suspect you'd be fine with the Amsoil, Mobil 1, or Redline products tested. Mobil 1 only just failed the minimum viscosity KRL-20-hr test which means it should be fine for the above application. Again, I think it gets back to specific applications. Remember, these are broad operating ranges that things are being tested at. If your application requires something to work at both extremes than it would make sense to run the Amsoil, if you're somewhere in between those extremes, than add a reasonable safety margin to your requirements and see what fits and use that or something better if you'd like.

Reason for
Bruce @ TTI recommending non shock proof is because the shock proof oils were too messy and stuck to the internals so well it made life difficult if he had any returns / repairs on his products ?
I run FUCHS Titan Supergear 75W90 oil in my TTI 5 speed and Redline lite weight shockproof in my AMC gearbox
Regards Mike