CitroŽn g/box Crown Wheel and Pinion - Page 9 - LotusTalk - The Lotus Cars Community
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post #161 of 229 (permalink) Old 11-28-2017, 09:53 AM
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My 2 cents...,here.

Price of 1650 euro, which Harry is asking, puts it in the ball park of mine! With shipping from Europe and duty fees, it will cost easily 2,100 USD, or more, per set.

Reversing the rotation will provide an additional 20% increase in strength.
In addition to this, my new design increases the pitch of both CW and pinion.
OE pinion gear, with its 8 teeth is the weakest link!
In contrast, my design reduces teeth count to 7 creating more room to increase the tooth thickness. That is the trick Harry's CWP-s would not have.
Cryo adds strength, but benefits may be limited without some meat on the bone.

Just to be complete. Your design might be stronger on the teeth, but it is more sensitive for pitting and makes more noise. Remember, Citroen is/was gear manufacturer and be sure, this ratio is by far the best for these gearboxes.

Reversing the rotation is upgrade, Klingelnberg is upgrade ( from Gleason ) so resuming: upgrade x upgrade= ........ the best.

cheers,

Harry Martens
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post #162 of 229 (permalink) Old 11-29-2017, 07:44 AM Thread Starter
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Citroen gearbox design is pretty old, conceived in late 50-s early 60-s.
In 50 years of existence, these boxes were coming in several different ratios, depending on the application, see attachment. Even you advertised several different ratios you had "in stock".

"Best" final ratio is determined not by the manufacturer, but by the particular Marque Ride Development Engineers on the basis of the desired dynamic performance of the vehicle.

Pitting is not caused by a difference in method of manufacturing, but due to... fatigue.
Tooth surface fatigue occurs when the load is applied on the tooth surface repeatedly, or when the force is applied on the tooth is larger than endurance limit of the material. As the result of the surface fatigue, the material fails and falls off the tooth surface.
When the tooth surface strength is insufficient against the load, the following countermeasures may be applied:
** Change the material to a stronger material having more hardness and thicker hardened "skin". Take sufficient consideration on the depth of the hardening layer during heat treatment, to ensure sufficient hardening layer, and to keep the gear surface strength.
Especially, as for the carburized gear surface, in consideration that the core material is low-carbon soft tissue, which cannot bear the surface pressure from the hard surface of the gear surface and leads to surface crazing and hole erosion; therefore, it is necessary to pay special attention to the depth of the carburized layer, hence the insufficient carburized layer gives rise to the insufficient surface pressure strength which leads to hole erosion.
** Enlarge the gear size (my 4.286 CWP has tooth thickness increased by 2mm)
** Enlarge the face width
** Correct improper tooth contact caused by bad mounting. By increasing stiffness, tooth contact improves.
And the most important:
**Provide appropriate conditions for the lubricant; proper type, viscosity, and quantity.

Last, but not least, the new 4.286 ratio (comparing to OE 4.357) increases the vehicle speed in gears bringing up the speed increase over stock gear UN1-26 to +1%, whilst OE 4.375 keeps it at subdued -3% to -6%. !
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File Type: xls C35 Citroen - Gear Ratios.xls (125.0 KB, 44 views)
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post #163 of 229 (permalink) Old 02-04-2018, 06:51 AM Thread Starter
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post #164 of 229 (permalink) Old 02-06-2018, 08:58 PM
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Originally Posted by dsvitesse1 View Post
Just to be complete. Your design might be stronger on the teeth, but it is more sensitive for pitting and makes more noise. Remember, Citroen is/was gear manufacturer and be sure, this ratio is by far the best for these gearboxes.

Reversing the rotation is upgrade, Klingelnberg is upgrade ( from Gleason ) so resuming: upgrade x upgrade= ........ the best.

cheers,

Harry Martens
DS-Vitesse ? Versnellingsbak revisie
Kudos to Harry for taking some real steps towards making the Citroen box more robust. It does need some help, and what Harry is putting together here looks like a very positive step.

And with regard to pricing, when it comes to transaxles for exotic cars, a couple thousand dollars to make such an improvement is good value. In some mid-engine exotic cars, the transaxle can be more expensive than the whole darn engine!
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post #165 of 229 (permalink) Old 02-13-2018, 07:50 AM
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Update 13-02. Pre turned and first gear cutting made.

cheers,

Harry Martens
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post #166 of 229 (permalink) Old 03-23-2018, 05:45 AM
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Hi there, I have a 1980 s2 with the Citroen C35 of course. From reading the posts am I to understand that there is an early and late C35 and my car being a 1980 will have the early. Also it sounds like the C&P up grade will only fit the later C35? Is this correct? Thanks Ross.
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post #167 of 229 (permalink) Old 03-23-2018, 06:03 AM
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Yes, your S2 should have the early 'box. Easily identifiable by having TWO fluid drain bolts (rather than only one).

That said, don't forget that the normally aspirated cars had less issues than the later turbos. Part of that is the shouldered input shaft VS the tapered shaft (which is what results in the circlip failure). So, the need to upgrade would not be as urgent.

If you are dismantling your gearbox, pay attention to the differential support bearings (in fact you SHOULD replace them). There are interesting upgrades on page 2 & 3 of this Topic.

Atwell Haines
'88 Esprit
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"Not all angels have wings." - Turbo R
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post #168 of 229 (permalink) Old 03-23-2018, 10:32 PM
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Final stage!!!!


cheers,

Harry Martens.
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post #169 of 229 (permalink) Old 03-24-2018, 06:31 AM
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Hi Carbuff, thanks for the quick reply. So my issue is that I have turbo charge the car with a stand alone "DTA" engine management system. So currently producing 300 hp @ the flywheel. So I would like to do the C&P fix with the ratio change. But some where I thought I read that it won't work with the early boxes. Is this correct? Thanks Ross.
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post #170 of 229 (permalink) Old 03-24-2018, 07:09 AM
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Hi, will fit all Citroen gearboxes. Either " previous" and "C35 " type.


cheers,

Harry Martens
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post #171 of 229 (permalink) Old 03-24-2018, 09:26 AM
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Thanks harry, wondering is my early trans not a C/35? If not what would my model # be? Also is there a quaiffe diff for my 1980 S2. What would the cost for the diff and your C&P. Thanks Ross.
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post #172 of 229 (permalink) Old 03-24-2018, 10:42 PM
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Ross,

Esprit S1/ S2/ S2.2/ S3 (C-??)
Lotus did not consider the early Citroen transaxle, as used in the naturally aspirated Esprits, to be strong enough for service behind the Turbo 910 engine. So design changes, most of which had more to do with materials & processes than in visually obvious configuration changes resulted in the...

Espirt Turbo, early = C30
While the basic gearbox remained fundamentally the same (with the exception of the clutch release lever moving from the top of the bell housing to the right side), a number of small revisions were made that were meant to increase it's torque capacity. An effort was made to remove stress risers (sharp grooves/ steps/ notches were removed), the heat treatment of gears was revised, etc, etc... a list of little things, but the main lump remained largely unchanged.

Espirt Turbo, 1984-onward = C35, torque capacity is about 215 Lbs-ft (Harry?)
More changes intended to strengthen the Citroen gearbox even further resulted in a completely new housing (all new castings). This was the last itteration of the Esprit-Citroen, and the strongest; however it's still considered the weak link behind the Turbo 910 engine. The next step up in power (torque) was going to require a different transaxle.

300 Hp going through an early naturally aspirated Esprit's Citroen transaxle?? That sounds a little optimistic. On the other hand, horsepower doesn't kill transmissions... torque kills transmissions. So, it all depends upon 'how' you're making all that horsepower.

Hp = (torque x Rpm)/5252, where torque = Lbs-ft. If you want more Hp, you can increase torque, increase rpm, or both. If you're still limiting the engine to a near-stock redline, and if you're getting an honest 300 Bhp, then clearly you've significantly increased the torque. The math doesn't cheat, so I'm a little dubious about putting that kind of power through a Esprit S2's stock Citroen gearbox.

Presumably, Harry's new CWP will increase the torque limit, but I've not heard/ read an up-rated spec.

*~*~*~*~*
Sidebar: Ever wonder why G-Turbo Esprits commonly have a problem with the spring-loaded input shaft working it's way past the circlip that retains it, then machining it's way into the back end of the crankshaft? We regularly hear stories about the next Turbo having that problem, or owners upgrading the circlip to a heavy duty snap ring as a pre-emptive strike to eliminate the problem before it occurs; but why don't we hear about that happening in the naturally aspirated Esprits? Well, simply because it 'never' happens to them.

One of the sharp transistions that was eliminated during the effort to reduce stress-risers was the stepped shoulder that the circlip bears against. It was replaced by a smooth taper in order to eliminate the stress riser, but the wimpy little wire circlip was NOT also upgraded at the same time. As a result, the new taper acts like a wedge that allows the input shaft (clutch shaft) to work it's way past the circlip. Once it escapes, all sorts of expensive things start to happen to G-Turbos that never happen to naturally aspirated Esprits.

'New' replacement input shafts are made to the older naturally aspirated configuration with the step.

Regards,
Tim Engel
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post #173 of 229 (permalink) Old 03-24-2018, 11:12 PM
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Illustration -- Citroen C35 Vs it's Predecessor

Here's a JPEG and a link to a PDF of the 1983-87 Federal Parts Manual page that 'Illustrates' the difference between the C35 and it's predecessor.

Regards,
Tim Engel
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File Type: pdf Esprit USA 1983-87 342 - 47.02A, Citroen, Old Vs C35, Illust, 195kb.pdf (194.6 KB, 47 views)

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post #174 of 229 (permalink) Old 03-24-2018, 11:18 PM
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Description -- Citroen C35 Vs it's Predecessor

Here's a JPEG and a link to a PDF of the 1983-87 Federal Parts Manual page that 'describes' the difference between the C35 and it's predecessor.

Regards,
Tim Engel
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Attached Images
File Type: pdf Esprit USA 1983-87 343 - 47.02A, Citroen, Old Vs C35, Text, 145kb.pdf (144.1 KB, 44 views)

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post #175 of 229 (permalink) Old 03-26-2018, 05:04 PM
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Hi Tim great information, thanks much
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post #176 of 229 (permalink) Old 03-26-2018, 05:13 PM
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Hi MRDANGERUS, could you please give some information on the purposed gear manufacturer of your gear sets? Thanks Ross
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post #177 of 229 (permalink) Old 03-27-2018, 08:54 AM Thread Starter
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Hi MRDANGERUS, could you please give some information on the purposed gear manufacturer of your gear sets? Thanks Ross
Gleason Inc, Rochester NY, USA.

Gleason is a great companyFor more information see: https://www.gleason.com/products

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post #178 of 229 (permalink) Old 04-09-2018, 06:40 AM Thread Starter
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Gleason proved this design and roll tested the prototype.
Design is ready for production run. I don't have enough group buy participants to start.
I'm playing Mega-millions, though.
If I win, I'm going to finance this endavour just by myself!
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post #179 of 229 (permalink) Old 04-12-2018, 07:34 AM
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Update 13-02. Pre turned and first gear cutting made.

cheers,

Harry Martens
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1st set in the shop!! More news soon, very soon.

cheers,
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post #180 of 229 (permalink) Old 04-12-2018, 08:26 AM Thread Starter
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