I'm delighted to report that both ourselves and Richard Gane have been accepted for CLM this year so there will be two Jupiters running in plateau two.
We have sent off the gearbox that Keith C very kindly provided and we should have it back in around 8 weeks.
Hopefully I've attached the proposed ratios for your interest.
I will try and keep the community updated!
Classic Le Mans 2020
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harrynaerger
- Posts: 23
- Joined: Wed Jun 05, 2019 9:02 am
- Your interest in the forum: I own a Jowett Jupiter which has been converted for historic racing.
- Given Name: Harry
Classic Le Mans 2020
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Keith Clements
- websitedesign
- Posts: 3968
- Joined: Wed Feb 08, 2006 11:22 am
- Your interest in the forum: Jup NKD 258, the most widely travelled , raced and rallied Jowett.
- Given Name: Keith
- Contact:
Re: Classic Le Mans 2020
Hopefully you will not run out of revs on the Mulsanne. The ratios are good for most short circuits, but suspect the long straight may stress the engine.
The Javelin ratios are listed in the competition tuning notes.
The later box=
1 1:17.4
2 1:10.6
3 1:6.7
4 1:4.875
Final 4.875:1
Harry's =
1 2.714
2 1.737
3 1.272
4 1
Final 4.56
For the Avon Turbo Steel as fitted to my Jup and Jav:
Tyre size
165/80R16
Measured at
PSI Bar
40.6 2.8
Diameter
Ins mm
26.73 679
Section
Ins mm
6.89 175
Revolutions
Miles Km
754.5 468.8
So the calculation with Jav diff:
revs per mile 754.5
max engine revs 5500
max revs at wheel in top gear with diff 4.875 = 1128
max revs/hr 67692
max speed mph 89.7
Harry's set up or mine in the Jup with TurboSteel tyre:
max engine revs 6500
max revs at wheel in top gear with diff 4.56 =1425
max revs/hr 85526
max speed mph 113
Now I run the tyre at lower pressure (32 psi) so rolling radius will be smaller (perhaps it increases up to the same value at max speed?).
What I had not considered before was the rpm drop differences when changing gear and how that affects acceleration times. Even if you got the gear changes exactly right, as fast as possible, you have to choose how to best use the torque of the Jowett motor and that depends on the cam profile fitted amongst many other things.
When my race/rally engine was in good tune I would take it above 7000 rpm (but only briefly) and I also have an overdrive fitted which speeds up some of the gear changes and gives more change points. Its only sustained running above 100mph was for half an hour on a deserted motorway in Europe. I am slightly more sympathetic with the current engine.
The Javelin ratios are listed in the competition tuning notes.
The later box=
1 1:17.4
2 1:10.6
3 1:6.7
4 1:4.875
Final 4.875:1
Harry's =
1 2.714
2 1.737
3 1.272
4 1
Final 4.56
For the Avon Turbo Steel as fitted to my Jup and Jav:
Tyre size
165/80R16
Measured at
PSI Bar
40.6 2.8
Diameter
Ins mm
26.73 679
Section
Ins mm
6.89 175
Revolutions
Miles Km
754.5 468.8
So the calculation with Jav diff:
revs per mile 754.5
max engine revs 5500
max revs at wheel in top gear with diff 4.875 = 1128
max revs/hr 67692
max speed mph 89.7
Harry's set up or mine in the Jup with TurboSteel tyre:
max engine revs 6500
max revs at wheel in top gear with diff 4.56 =1425
max revs/hr 85526
max speed mph 113
Now I run the tyre at lower pressure (32 psi) so rolling radius will be smaller (perhaps it increases up to the same value at max speed?).
What I had not considered before was the rpm drop differences when changing gear and how that affects acceleration times. Even if you got the gear changes exactly right, as fast as possible, you have to choose how to best use the torque of the Jowett motor and that depends on the cam profile fitted amongst many other things.
When my race/rally engine was in good tune I would take it above 7000 rpm (but only briefly) and I also have an overdrive fitted which speeds up some of the gear changes and gives more change points. Its only sustained running above 100mph was for half an hour on a deserted motorway in Europe. I am slightly more sympathetic with the current engine.
skype = keithaclements ;
-
Keith Clements
- websitedesign
- Posts: 3968
- Joined: Wed Feb 08, 2006 11:22 am
- Your interest in the forum: Jup NKD 258, the most widely travelled , raced and rallied Jowett.
- Given Name: Keith
- Contact:
Re: Classic Le Mans 2020
I have booked the ferry and have a cabin going overnight on 30th June and back Tuesday 7th July, so a couple of nights to find a chateau to enjoy. Hopefully my Jup will not be required as spares for the two racing Jups!
skype = keithaclements ;