Lotus Elan

6 speed gearbox for the Elan

PostPost by: msd1107 » Mon Jun 29, 2009 12:28 am

Thanks Gary,

So it appears the MX5 uses a bolt-on bellhousing after all, just very long. Take off the MX5 bell, machine an adapter plate so that it bolts to the Cortina bell. This is good news/bad news. First, it brings the gearbox forward, which minimizes the effort in relocating the shift lever. The bad news is that the input shaft is too far forward and the output shaft is too far forward also.

If the original gear cluster is retained, we need a new drive shaft. The gearbox needs to be disassembled and the input shaft machined.

A new gear cluster would just have the proper dimensions specified in the design.

It is not obvious from the diagrams just how much latitude there is in moving the shift lever forward and shortening the shift rods to match.

If the tack is taken to go 4th direct with OD 5th and 6th, how to re-engineer the shift linkage to get the proper h-pattern shift? I doubt that many people want to learn to shift 1st, 2nd, 3rd, 5th, 4th, 6th!

If we don't go 4th direct, we need a higher differential ratio, which topic has received attention in the past.

The MX5 and IS-300 had a variety of differential ratios and tire sizes during their history, so it is probable there are several transmission to speedometer drive gears. We need 4 different ones to accommodate the various common combinations of tires, differential ratios, and speedometer turns/mile figures. Or do they even use a mechanical connection between the gearbox and speedometer?

Has anybody heard back from Vincent? Otherwise, we are just pounding on our keyboards for nothing.

David
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PostPost by: steveww » Mon Jun 29, 2009 2:48 pm

I have been to see work in progress so far.....

The gearbox is a neat fit in the chassis but it does fit with out any cutting to the chassis. The gear lever aligns with the hole and the cable drive for the speedo works. They are just finalising the design for the clutch slave cylinder, looks like a remote bleeder will be required. The Lucas starter does not fit so a TTR type pre-engaged type will have to be used, as this is an improvement I can't see too many objections here.

The six speed close ratio gearbox will really suit the character of the Elan, much more so than a Type 9. With 6th being 0.84 this gives approximately 83 MPH with 3.77 diff or 88 MPH with 3.55 diff @ 4000 rpm.

They hope to have a prototype on the road in August.

Before you ask there are deliberately no pictures at the moment, a certain amount of intellectual property needs to be protected at this stage.
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PostPost by: gjz30075 » Mon Jun 29, 2009 3:36 pm

Steve, looks like you're our 'go to ' guy for this project. Keep us posted!

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PostPost by: JJDraper » Mon Jun 29, 2009 5:13 pm

Worth noting that the clutch slave will be on the other side from normal, so away from the exhaust.. and shorter hose run (for RHD). Can't wait to try it!

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PostPost by: bcmc33 » Mon Jun 29, 2009 9:57 pm

I would expect co-axial clutch actuation on this gearbox.
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PostPost by: Jolly Jumper » Tue Jun 30, 2009 9:58 am

Guys,

why not just wait and see what Mr Haydon comes up with? I have seen it on several message boards that new ideas and products were discussed to death by people who would never buy the product anyway. Let's see what comes next. Steve, keep us posted. A modern gearbox would make the Elan better suited to todays traffic.
Last edited by Jolly Jumper on Tue Jun 30, 2009 4:01 pm, edited 1 time in total.
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PostPost by: GrUmPyBoDgEr » Tue Jun 30, 2009 10:23 am

Jolly Jumper wrote:Guys,

why not just wait and see what Mr Haydon comes up with? I have seen it on several message boards that new ideas and products were discussed to death by people who would never buy the product anyway. Let's see what come next. Steve, keep up posted. A modern gearbox would make the Elan better suited to todays traffic.


I'm also very interestd in the progress that the G/box makes but second the motion.
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PostPost by: bcmc33 » Tue Jun 30, 2009 12:39 pm

I for one will put the T9 project on hold until this one emerges for a full review.
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PostPost by: garyeanderson » Tue Jun 30, 2009 2:03 pm

TRD offers a close ratio set for the 6 speed
The ratios are as follows
Close stock
3.106 3.874
2.175 2.175
1.585 1.484
1.223 1.223
1.000 1.000
0.869 0.869

http://trdparts.jp/english/list_race-mis_sxe.html
has prices in yen, convered to USD about $2300

http://www.toymods.net/forums/showthread.php?p=971026
J160 = Aisin Industries AZ6. Same gearbox(essentially) is used in the Miata, RX8, and S15, and SXE/GXE10.

S15 6 spd 3.626 2.200 1.541 1.213 1.000 0.767
RX8 6 spd 3.760 2.269 1.645 1.187 1.000 0.843
Miata 6-spd 99- 3.760 2.269 1.645 1.257 1.000 0.843
SXE10 6 sp 3.874 2.175 1.484 1.223 1.000 0.869
TRD(33030-SE100) 3.106 2.175 1.585 1.223 1.000 0.869
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PostPost by: msd1107 » Tue Jun 30, 2009 9:52 pm

Gary,

Thanks for all the different iterations of ratios for the gearbox.

elan-f15/more-spreadsheets-t15049.html.


A previous post at viewtopic.php?t=16413&view=next, down at the bottom, 20080411zGearRatios.xls, allows you to mathematically view various properties of any gear box ratio set.

What follows is an extract of the information for the 5 gearboxes. This is based on a hypothetical car with 155/80-13 tires, 3.55 differential, and 6,500 RPM. If anyones setup is different, download the spreadsheet and input the information.

For each gearbox, the information extracted is as follows: "Gb ratio" is the gearbox ratio, in 1st through 6th from top to bottom. "% diff" is the percentage difference between the current gear and the next gear. "speed" is the speed achieved at 6,500 rpm. "diff" is the difference in speeds achieved in the current gear and the next higher gear. "err" is the error term for this gear and the next gear when the program calculates the Figure of Merit (FoM). Zero is best, low single digit figures OK, larger figures not OK. The math is simple, the results illuminating. "FoM" is the Figure of Merit. This is a mathematical calculation as to how well the gear ratios are staged. The maximum is 100, and there theoretically is no minimum. You will perceive a gearbox with a FoM above 80 as being a well staged set of gears. By the time the FoM gets down to 0, there will be awkward gaps between one of more ratios, either too wide or too narrow a gap.

TRD 33030-SE100
Gb ratio % diff speed diff err..FoM=-21.9
3.106....42.8...038.7..16.6..13.7
2.175....37.2...055.3..20.6..02.3
1.585....29.6...075.9..22.5..13.3
1.223....22.3...098.3..21.9..05.3
1.000....15.1...120.3..18.1..14.2
0.869.............138.4

MX-5 ?99 on
Gb ratio % diff speed diff err..FoM=68.5
3.760....65.7...032.0..21.0..00.2
2.269....37.9...053.0..20.1..03.5
1.645....30.9...073.1..22.6..00.4
1.257....25.7...095.7..24.6..06.0
1.000....18.6...120.3..22.4..02.5
0.843.............142.7

SXE-10
Gb ratio % diff speed diff err..FoM=-51.6
3.874....78.1...031.0..24.3..00.4
2.175....46.6...055.3..25.7..15.0
1.484....21.3...081.0..17.3..36.4
1.223....22.3...098.3..21.9..08.9
1.000....15.1...120.3..18.1..00.0
0.869.............138.4

RX-8
Gb ratio % diff speed diff err..FoM=-156.7
3.760....65.7...032.0..21.0..01.0
2.269....37.9...053.0..20.1..06.6
1.645....38.6...073.1..28.2..72.5
1.187....18.7...101.3..18.9..22.6
1.000....18.6...120.3..22.4..00.0
0.843.............142.7

S15
Gb ratio % diff speed diff err..FoM=-308.6
3.626....64.8...033.2..21.5..09.2
2.200....42.8...054.7..23.4..03.4
1.541....27.0...078.0..21.1..21.4
1.213....21.3...099.2..21.1..66.8
1.000....30.4...120.3..36.5..62.7
0.767.............156.8
If 5-6 is not included in FoM calculation, FoM improves to 72.8.

The last set takes Bills suggestion of using a 1st similar to the BGH 5-speed, with 4th direct and OD on 5th and 6th. The program uses the basic gear tooth parameters that would be in a T-9 gearset. Here you see the benefit of the program generating an optimly staged set of ratios. Given only a few pieceds of data, the program returns the 6 gear pairs to generate the gearset. This first time effort returned a FoM of 94.2, not too bad.

Bill?s hypothetical 2.66 1st, 4th direct,
Gb ratio % diff speed..diff.....err...gears..FoM=94.2
2.654....56.9...045.3..25.8..00.6..13:30
1.691....33.7...071.1..24.0..01.6..17:25
1.265....26.5...095.1..25.2..00.1..20:22
1.000....20.8...120.3..25.0..00.0..32:20
0.828....17.0...145.3..24.7..00.0..25:18
0.708.............169.9.................26:16

Looking at all the examples, for the non-TRD gearsets, 1st is basically a throwaway startup gear. 6th is not enough of an overdrive ratio. The MX-5 ratio staging is OK, but the others have strange gaps.

Interesting

David
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PostPost by: gordonlund » Tue Jun 30, 2009 9:58 pm

Am I speaking out of turn here. I find with my +2 that the original Ford 2000E box mated to a 3.54 diff does everything I need. Ok you use 3rd gear a bit more if you want to go a bit, but don't forget, unlike a K series, the Twink has a fairly flat torque curve at the top end, and does not really need endless gears. 50 cc Kriedler 4 speed box coupled to a 3 speed derailier syndrome springs to mind!!

I don't want to tow a caravan either.

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PostPost by: Elanintheforest » Tue Jun 30, 2009 10:05 pm

I agree, Gordon, and I still haven't found a nicer box to use on any moderns. I guess that having an overdrive top is useful in dropping the revs, but it doesn't allow a faster top speed to be maintained any better...the wind noise from the doors takes over from the ngine noise at 100mph plus.

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PostPost by: garyeanderson » Tue Jun 30, 2009 10:19 pm

gordonlund wrote:Am I speaking out of turn here. I find with my +2 that the original Ford 2000E box mated to a 3.54 diff does everything I need. Ok you use 3rd gear a bit more if you want to go a bit, but don't forget, unlike a K series, the Twink has a fairly flat torque curve at the top end, and does not really need endless gears. 50 cc Kriedler 4 speed box coupled to a 3 speed derailier syndrome springs to mind!!

I don't want to tow a caravan either.

Gordon


Hi Gordon

I agree that it a nice combination and anyone thinking of an upgrade should try this first as its is effectively a .90 overdrive if you had a 3.9 in all gears for reasonable money. I can't imagine that the box when it is finally available for sale will be inexpensive and if I were going to spend that kind of money I would do a lot of other things first. in the mean while, waiting for summer to arive and April to end. 21 days with rain in June...
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PostPost by: msd1107 » Tue Jun 30, 2009 10:27 pm

Gordon,

Many people will agree with you. After all, this is what we live with, and are used to.

I have had the 165-13 with 2.51 1st and 3.55 differential combination for 30+ years now, and have always felt the car to be under geared. I have taken many long trips at 4000-4500 because that was what was necessary. On a return trip from the historic car races, I followed a Porsche and Ferrari at over 6000. Good thing they didn't try to leave the little car behind.

There are several posts and contemporaneous road tests that ran up to 7000 in top and complained they needed more. If you have a modified engine, this is even more noticable. Of course, there are not many chances anymore to pull max rpms in OD top, but the design objective is to gear for what the car is capable of.

Mark

If you think the Lotus box is the best, you should drive an Elite with a T-9 conversion. There were not very many done, so it is probably difficult to find one to drive. The Climax pulls the .82 OD 5th just fine and the shift action is to die for.

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PostPost by: garyeanderson » Tue Jun 30, 2009 11:21 pm

If I spent most of my driving at 80mph and up I would want an effective O.D. too. But I don't, I can choose roads that don't force you to keep up with other modern cars. When I started to beat the 3rd gear syncro to often I used to mostly use 1st, 2nd and 4th with the 3.9 and ultra close box, granted its a 1700 cc engine and under 1500 pounds with me on the road. I can't imagine what you would do with any of these 6 speeds with one underdrive and one overdrive gear. I guess if you swap the box out you might as well keep going and pop in the S2000 engine along with gearbox, that would eliminate all of those clutch, bellhousing, and starter issues and leave only a few extra problems to sort...
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