Lotus Elan

Quantum Mechanics/John Esposito's 5-speed Offering for Elans

PostPost by: bill308 » Wed Aug 19, 2009 12:37 am

Hi all.

There has been a lot of interest over the years concerning a better gearbox for the Elan. John Esposito of Quantum Mechanics in Monroe, CT USA now offers a 5-speed gearbox with a choice of ratios. The box assembly is based upon the Ford t9 and utilizes John Voight's conversion that adapts the t9 for use on Elans and probably Cortinas and Lotus Sevens. Most importantly, alternate gear ratios are now made available courtesy of BGH Gear Tech. John's announcement has been posted in another thread but I repeat it here.

download/file.php?id=7076

download/file.php?id=7075

What John has done is pull together disparate parties to offer a really good solution to living with an Elan in today's world. Interstrate traffic here routinely flows at 80+ mph. Relaxed cruising at these high speeds is really desireable.

I don't know if this gearbox will ever be legal in the racing world. The argument I would make before a santioning body is that it does not offer performance advantages except maybe in an endurance races. The fact is that this gearbox offers performance gear ratios between the semi close ratio and close ratio Lotus offerings. It offers a potential higher top end, but probably weights more, even with the optional alloy t9 casing. It is unlikely that top gear would be used in normal circuit racing unless rear end ratios were adjusted numerically higher. The fact that all housings would be aluminum, means that oil control should be very good, due to similar coefficients of themal expansion. In other words, the gasket interfaces will change with temperature at about the same rate.

The real beauty of this gear box is it enable's relaxed high speed cruising.

For those of you contemplating a 5-speed gear box of this type, I offer the attached Excel file plotting some of the more desireable ratios that are available.

Data labels for the individual ratios for each gear set are alligned vertically. The height of the label corresponds with the plotted point at the 1-5 positions. For the Lotus 4-speed ratios, only 4-points are shown.

The legend connects the plots to specific BGH offerings and compares them to the Lotus semi close ratio and close ratio offerings (in heavy dotted lines). This provides a basis for gear ratio comparison. Not all BGH ratios are shown, only those I've selected for comparison. In my opinion these are the ratios of interest.

Want the closest thing to a close ratio gear set but a 0.82 OD, slelect the E7A gear set. Want the closest thing to a Lotus semii close ratio gear set, select the E2A gear set.

For me, I selected the E7A gear set. This gear set offers gear ratios between the close ratio and semi close ratio gear sets, but closer to the close ratio gear set. First gear is a bit lower, but the following ratios are very close to the close ratio ratios. I think this fits my S2 very well in that it provides a slightly lower first gear for starting on hills, but close to the close ratio gear set, making it better for my driving style. First gear is a little more friendly than the close ratio for starting on a hill, but also makes first gear more user friendly for general use. Somone with a +2 or heavier baby Elan, might want to consider the E7E offering that substitutes the E7A's 2.66 first gear for the E7E's 2.75 first gear. It was a tough call for me with my S2 and 3.55 rear end. For someone who just wants an OD for cruising, select the E2A ratio.

The E7A, E7E and E2A ratios provide a 0.82 OD transmission ratio in fifth gear. This results in an 18% reduction in top gear rpm for a given speed.

Bill
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PostPost by: msd1107 » Wed Aug 19, 2009 3:06 am

Excellent spreadsheet Bill.

The enclosed spreadsheet contains a bunch more information for each of the gear ratio sets. This data is all for 155-13 tires, a 3.55 differential, and 6500 rpm.

The spreadsheet that generates this data can be downloaded at viewtopic.php?p=82911 at the bottom so if your car is different from the above defaults, download the spreadsheet.

There are four sets of data for each gearset.

The first is technical data about the gear ratios. For explanation of each of these fields, read the help text in the downloaded spreadsheet.

The next is a table of MPH vs RPM for each gear. This shows you the speed in any gear at a particular RPM.

The next is a table of RPM vs MPH for each gear. This lets you see the rpm necessary for any speed and gear.

The last is an upshift/downshift table. This lets you see what happens to the rpms when you upshift or downshift. The table is for each gear in a column. For a particular gear, the rpm for that speed is shown, and going down or up the rows shows what rpm you would get shifting up or down.

For instance, the speed in 1st gear varies from 47.9 in the Lotus 2.51 1st all the way down to only 33.0 for the standard T9. The BGH E7 is 45.2 for the 2.66 1st or 43.7 for the 2.75 1st. The BGH E2 is 40.4. The heavier +2s might choose this one.

Incidentally, I have driven a T9 conversion in an Elite, this with the 2.75 1st. This combination works just fine, and a +2 probably could live with it. Notice the Figure of Merit is slightly greater with the 2.75 1st over the 2.66 1st so it is your call as to whether you want the closer 1st-2nd shift of the 2.66 or not.

Have fun with this!

David
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PostPost by: cabc26b » Wed Aug 19, 2009 2:24 pm

Hi David,

This a great spreadsheet - I was looking to see if you were doing calculations off any of the cells ? reason being is that I am running a 3.9 rear end and wanted to see what the numbers look like with the different ratio -

Any assistance would be appreciated -
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PostPost by: john.p.clegg » Wed Aug 19, 2009 3:45 pm

Isn't it just divide by 3.55 and multiply by 3.9 (or vice versa?) ie x1.124
(or vice versa?)ie x0.91


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PostPost by: msd1107 » Wed Aug 19, 2009 5:06 pm

cabc26b,

Perhaps the easiest way is to download the spreadsheet at viewtopic.php?p=82911 at the bottom. This allows you to input any ratio set and look at the results. It also has additional charts and graphs.

If you want to compare and contrast, print one set (2 landscape LaserJet pages or select the print option to print on 1 page), enter the ratios for the next gear ratios set of interest and print that, etc, etc.

The way I generated the spreadsheet is as follows, for those of you with high tolerances for pain and frustration.

Download the speadsheet above. Open it. On sheet Gearbox, right click, select "move or copy", select box make a copy, and select the sheet after gearbox to copy the spreadsheet.

In the new sheet, select it all and delete everything. Select all the light blue boxes. Key Alt O, D, and type D's until all the fileds are deleted.

Select any rows that have multiple columns in a field and delete those rows.

Go back to sheet Gearbox. Enter your tire size data, rpm data, and differential ratio. If you want kph, select that option. Delete cells B19-B25.

Enter the gear ratios in the first gear set of interest in B19-B22 or B23.

Select rows 15-22 or 23. Enter Cntrl C for copy. Select the new sheet. Select the top left cell. Enter Alt E, S, V and Alt E, S, T to copy the values and formats of the data in sheet Gearbox.

Go back to sheet Gearbox. Select rows 45-50 or 51. Enter Cntrl C for copy. Select the new sheet. Select the left cell in a row under the before data. Enter Alt E, S, V and Alt E, S, T to copy the values and formats of the data in sheet Gearbox.

Go back to sheet Gearbox. Select rows 57-62 or 63. Enter Cntrl C for copy. Select the new sheet. Select the left cell in a row under the before data. Enter Alt E, S, V and Alt E, S, T to copy the values and formats of the data in sheet Gearbox.

Go back to sheet Gearbox. Select B69-H74 or H75. Enter Cntrl C for copy. Select the new sheet. Select the left cell in a row under the before data. Enter Alt E, S, V and Alt E, S, T to copy the values and formats of the data in sheet Gearbox.

Repeat as necessary for all the gear ratio sets in which you are interested.

Now you can be just as geeky in analysing gear ratios as the most rabid enthusiast!

Have fun.

David
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PostPost by: cabc26b » Wed Aug 19, 2009 5:55 pm

David- Thanks for the pointers - looking at the post there are lots of sheets I down loaded your last post on page 1 < I will Digest your comment and play around with the data ( I am running a 3.9 diff) tires will be 21-22.9 depending on what's mounted.

John - I did the divide multiply logic for 5th gear to see what the cruise speeds were.

I now need to select my gear sets before I send off my money ... I'm thinking i may be fine with a 2.7 or 2.6 1st.

George
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PostPost by: bill308 » Thu Aug 20, 2009 12:10 am

My initial post presented a graphical comparison of the better gear set candidates. I?m attaching an updated spreadsheet whose only changes from the original are the deletion of Chart1 (unrefined) and I set the default magnification to Chart2A to 75 % verses the original?s 200 % magnification. One now views the chart in its entirety as the default view. For a closer look, just change the magnification within MS Excel.

Probably the best way to begin looking at this chart is to first identify the Lotus Close Ratio (LCR) trace, the bottom trace. Then note the Lotus Semi Close Ratio (LSCR) trace. To a large degree, I think these 4-speed gear sets establish a known reference envelope. The LCR gear set in my mind has an acceptable, but long first gear. It can be a little touchy in stop and go traffic or starting on a hill with a load. After that it?s a hoot, closely spaced, and appropriate for performance, until it runs out of gears. The LSCR is probably a bit too low in first gear for my liking. This gear set is pretty good at crawling around in stop and go traffic. I found I could mitigate the worst of this driving condition by merely engaging and disengaging the clutch without having to apply the accelerator, despite a low inertia flywheel. The 2-3, gearshift feels pretty wide for my liking and to a lesser degree, so does the 3-4 gearshift.

Enter the world of alternate gear sets. As one compares the different gear sets, those that fall within the 2-Lotus offerings, will have characteristics within their bounds.

With respect to interpreting trace shapes (curvature), a more pronounced curve means wider ratios, while a flatter curve means tighter ratios.

My take on the t9 offerings.

Standard Sierra-2L Great for pulling stumps.

2.8 Close Ratio Can only pull small stumps with this one but useable on the road. The 1-2 g gear shift is very tall. After that it looks very good. I believe Burton Power offers an alternate first cluster kit that yields a taller (2.9-3.0) first gear. I think this would be a big help but see if it makes financial sense. It just may.

E2A This is really a LSCR feel box, but with a worthwhile 0.82 OD fifth. If you like the LSCR box, you?ll love this gear set.

E3A Here is where things start to get interesting. First gear cluster (2.92) is a little taller than the LSCR box and the second gear cluster is even taller, but only a little. The best available OD fifth is 0.83.

E7A The first of the performance gear sets. It and its sister E7E, have up until now been built to a heavier duty specification, like larger bearings, supposedly good to 250 Lb-ft of torque if I remember correctly. Expensive. A 2.66 first gear cluster is getting close to the LCR?s 2.51 and all following ratios are also pretty close to the LCR. The OD fifth is 0.82.

E7E This selection differs from the E7A for the first gear cluster only. A 2.75 ratio is substituted for the 2.66 of the E7A. This is almost exactly between the LSCR and LCR first gear ratios.

I hope this helps.

Bill
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PostPost by: RotoFlexible » Thu Aug 20, 2009 2:06 pm

bill308 wrote:The LCR [Lotus Close Ratio] gear set in my mind has an acceptable, but long first gear. It can be a little touchy in stop and go traffic or starting on a hill with a load. After that it?s a hoot, closely spaced, and appropriate for performance, until it runs out of gears.

Bill notes in his original post that his S2 has a 3.55 diff. For those of us still enjoying (or saddled with, take your pick) the 3.9 diff, first gear is just fine, but the "running out of gears" problem is much worse. A slow-lane highway speed needs in excess of 4,000 rpm, increasing as you move to the faster lanes.
The E7 partially solves this problem with its .82 top gear, but revs are still above 3,200 on the highway. I'd prefer something closer to 3,000. I think the E7 with the 2.66 1st would match up well with a 3.7 (3.77?) diff, getting 1st back near its original overall ratio and lowering highway revs a little further.
I need to do some research to figure out if this conversion will work with my heavy-duty clutch. If it appears that it will, I think my check will be in the mail. It's expensive, but if I don't do it, I'll kick myself every time I pull onto a highway.
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PostPost by: cabc26b » Thu Aug 20, 2009 2:40 pm

I meant to ask yesterday if a tilton set up was possible to use with the T9, ditto a gear reduction starter, does any one know ?

George
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PostPost by: bill308 » Fri Aug 21, 2009 12:30 am

George,

I would think the Tilton would be a possibility. It's all Lotus Cortina to the Flywheel. The Kit provides a clutch cover, friction plate, a concentric slave cylinder. and I think fittings to enable external bleeding of the slave cylinder. I see no reason why a geared starter would not work. I'm not familiar with the Tilton clutch assembly but surely they have a clutch cover that will bolt up to a twincam flywheel and indeed a Tilton flywheel (not sure if they still make it though).

There are at least 3-issues that need to be checked; clearnce to the T9 belhousing; spline details (You may be able to deal with this with an optional friction plate); clutch cover interaction with the concentric slave cylinder (maybe shimming addresses this).

Bill
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PostPost by: RedS4 » Fri Aug 21, 2009 1:14 am

RotoFlexible wrote:
bill308 wrote:The LCR [Lotus Close Ratio] gear set in my mind has an acceptable, but long first gear. It can be a little touchy in stop and go traffic or starting on a hill with a load. After that it?s a hoot, closely spaced, and appropriate for performance, until it runs out of gears.

Bill notes in his original post that his S2 has a 3.55 diff. For those of us still enjoying (or saddled with, take your pick) the 3.9 diff, first gear is just fine, but the "running out of gears" problem is much worse. A slow-lane highway speed needs in excess of 4,000 rpm, increasing as you move to the faster lanes.
.


A previous owner of my car fitted a 4.1 diff (ex Escort van! :? ) as the car was used on track occasionally. Has anyone done this in the UK or US ? (My first post! :D )
Evan J
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PostPost by: msd1107 » Fri Aug 21, 2009 3:16 am

George,

These sort of interface questions show the problems involved in adapting to non-standard components.

Some time ago, I wrote to John saying if he was going to get more than a nominal number of gearsets, he should specify that BGH furnish them with Lotus compatible spline diameter and number. That way, the BGH kit would not need a U-joint adapter and a clutch and would not have to deal with Lotus owners who had already modified their cars. It also decreases the cost of the kit for those who specify the BGH gears.

The same argument holds with the aluminum gearcase. It should have a bolt pattern for the Lotus bell housing. This minimizes the cost and shipping of the kit when ordering the optional gearcase and allows the Lotus owner to use whatever bell housing they already have, whether iron, aluminum, or magnesium. Now, if the owner has upgraded from the standard bellhousing, they are doubly SOL.

Maybe it is not too late to make a change. I wouldn't mind waiting.

David
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PostPost by: msd1107 » Fri Aug 21, 2009 3:27 am

RedS4,

Differential ratios of 4.11 and lower are used in racing. At 9000, even a 4.56 differential is good for 130 mph, and many circuits can be geared even lower.

For the street, the problem is that no transmission speedometer drive gears are available for differentials lower than 3.9. You are marginally ok with a 4.11 if you run 165-13 tires. Otherwise, the odometer and speedometer read fast. You can always send the speedometer away to a rebuilding service to have different gears installed in the speedometer to bring the calibration back.

David
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PostPost by: RedS4 » Mon Aug 24, 2009 9:45 am

Hi David
Thanks for the advice. :) If i do change the diff it will be back to a ratio closer to standard - and maybe limited slip. Having said that, the idea of having a speedo reading slightly high isn't such a bad thing here as many "cameras" are hidden.... :evil:

The two (fulltime) tracks in NSW are very different - one is short (4.11 would be perfect), whereas the other is a difficult one to set up for as it has both a long straight some shorter ones and many tight curves.

Thanks again.

Evan J
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PostPost by: msd1107 » Mon Aug 24, 2009 5:28 pm

Hi Evan,

I forgot to mention, but there is a downloadable spreadsheet at elan-f15/updated-spreadsheets-t18445.html at the botton that deals with the issue of speedometer drive gears.

So no matter what tire, differential, and speedometer turns/mile you have, it will tell you the best speedometer drive gear. And if that gear is not available (there are only 3 for the gearbox) the spreadsheet will allow you to determine the appropriate odometer gears in the speedometer so that a Smiths repair facility can give you a properly calibrated odometer/speedometer.

There is one thing that is not usually considered. You can change speedometers from differen years to possibly get a better calibration. The early Elans had 1000 turns/mile. S4 and on had 980 turns/mile. I am not sure/ but there was a +2 or Europa speedometer with 940 turns/mile. The Elan speedometers turn up on Ebay from time to time. I'm not sure about the 940 turns/mile one, though.

In any case, you can satisfy any questions you have by fiddling around in the spreadsheet.

Gearing for different track conditions is a different subject. Generally speaking, and depending on engine rev range and differential, the CR gearbox will see you through a course from about 25-130 mph. If you need 130, but the minimum speed is less than 25, you could live with low rpms out of slow speed corners or swap in a semi-close ratio transmission. If your courses are less than 130, you can use different differential ratios. But if you race on widely disparate courses, you can either live with a compromise setup or spend time between races swapping in different transmissions and/or differentials (not to mention the cost of the extra components).

There is another downloadable spreadsheet at viewtopic.php?p=82911 at the bottom that allows you to input your car parameters and see charts and graphs of the gearbox ratios and speeds and rpms. You can fiddle with either of these until you are blue in the face and hope that the cars' performance is worth the effort.

David
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