the gearbox faults

[Günter]

Hello folks! B)

My idea was to use the worldwide gearbox problems as an example for an documentary/ technical calculation project in my studies. The teacher thinks it must be possible for me to calculate the loads and stresses in the shaft, and find all mistakes in the original Renault concept (for example to add an fifth gear with an overhang after an step in the diameter/after an bearing).

I hope you all don't misunderstood that , it is not my plan to invent an other upgrade. That's not my area!

What I'm interested in is as follows: find a better [theoretical!]project for technical calculations in my examinations than the existing ones. Those are more related to child seats, roof-racks , hydraulics and other mechanical stuff. But nothing from a real car

If i can ever finish my studies in the far far future, than I'm really not interested in "child seat"-engineering

back to topic:

1.) - i think i need all dimensions of the main shaft and the alloy number (for cross-reference in international material data sheets), the only thing that i know is the torque that is coming from the engine (V8/ 4-cyl.) and the gear setting.

2.) - i also need to know the common stress situations in witch the gearbox mostly fail in the 5th .

So if someone has to tell his personal experience, please note rev.-situation (or what you have done as it happens), and maybe ground-speed or anything else to illustrate it. I have to find an common situation!

Edited April 5, 2008 by G

[Günter]

hey, what's wrong with all the global Lotus owners ? I taught some gearbox really had a fault in the last 20 years ?!

Or is that all a lie , and the Renault-Box lasts for ever and can resist all power load you can get at...

Again, i just want to work on an interesting calculation project. Nothing with "get in opposite" to EMCO, BELL, GTO .. I's all theoretical stuff!

[peter_england99]

G

[scuba1099]

I just lost the Crown Wheel about 2 weeks ago. When it was taken apart, 3 teeth had come off. I had just upshifted to third and was running about 3500rpm (I think). It must have been in the works for some time, I've only had the car 4 months and don't know how the PO drove it.

[Günter]

Peter, same problem on my. I wasn't the owner as it happens. The snap/lost of 5th gear was under the previous ownership.

As i now read it is mostly common to have (racing related) problems in second gear, hmm... lets me think to change the point of concentration. But i am still more interested in the split of/snap of from 5th. As i can compare that with my own car.

And i also hope the calculations are easier to handle in the end of the shaft.

So i still need measurements and material data of the original shafts, otherwise i have to open my own (but never touch a running system, right ?! )

[andydclements]

You can probably sum up the most common issues as these two.

2nd gear, issues with synchro ring leading to cog damage due to driving style

5th gear shaft snapping due to excessive power from engine.

I have heard of a few crown wheel issues, but it's probably not as common as the top 2.

Andy

[Günter]

as i have not learned/ or does actually not learn something about wear of syncros, i go with power vs. 5th gear stability /shaft weakness. "Sigma" and "Tau" is my world in the moment, and a bit construction factors coming from gaps, groves, ring-shapes and so on.... .

[M3S2k]

Appear to have had the crown wheel issue last wednesday. Problem occurred when taking off at a green light from a standstill. No hard acceleration just normal leisurely take-off. Was probably doing 10 mph in 1st gear when first heard the noise.

[gmendoza]

5th gear failure is also sometimes caused by excessive heat weakening the shaft due to low oil.

[peter_england99]

G

[Tony94S4]

I am in a process of making my own spec primary shaft in the next few or more weeks,

having 2 boxes I can loan u my primary shaft and 1st & 2nd gear if u wana study it

well if u need I can send u the crown wheel and pinion the whole assembly also but shipping and insurance to Germany will probably be a lot

or I can just get u the mesurments u need, the machine shop that I will take the assembly to will get tham all for me before we decide where to upgrade

let me know

tony

Edited April 9, 2008 by Tony94S4

[Günter]

what i need mostly is all exact measurement (possibly coming direct from the blueprints, data sheets of the original workshop-books) . As i only have my own dyno data, the gear settings [without information about tooth profile !?] and the Lotus Press release with torque figures. In the UN-1 workshop book (wich i have got now) is only all maintenance and repair information. Nothing with measurements from the original drawings. I do not want "secrets" from the various upgrade-kits. Just the data from the original Renault box, as in use by Lotus.

I think the teacher will give me the conceptional formulation to calculate why it fails, and after witch time of use. Maybe with some FEM illustrations or so. But i don't know it exactly in the moment.

I don't care what Derek Bell, Kevin at GTO or any other wants to do with the results. It's just a "play with interesting numbers" in my case. If it passes the evaluation ,i can give it to all involved persons!