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Hi Duncan,
Martin here from California (aka Hassleweed on the Locost USA forum). You were kind enough to introduce yourself on my Tesla powered Seven build. I wanted to thank you as I now am going to use the Chevy Volt battery pack. The batteries I was planning to use have been shutdown - LG Chem has been issuing cease and desist letters - and so I have ordered a 2nd Gen Volt pack. Thank you for the suggestion. I'll be digging around your blog for how to get it working!
Cheers
Martin
 

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Discussion Starter · #322 ·
Hi Guys
Bit of a gap - went to a Tarmac Autocross at Teretonga yesterday

Car went well
But I have identified a problem - its not been that quick at these events
Yesterday it was blindingly obvious that my front grip was severely lacking!!


My back tyres are competition tyres - very grippy
My front tyres are the ones that were on the rims when I got them! - normal saloon tyres at least 12 years old

I have ordered another pair of sticky tyres - these are slightly taller and wider than the ones I have just now so they will go on the back and my lovely Nittos will go on the front

Its our annual Drag races on Sunday the 21st of February - will see how that goes
 

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Nice Work Duncan. Looks quick on a tight course. I've probably mentioned it before but bang for buck I love Nankang AR1 for a light car. Apparently they aren't so good on a heavier car.
 

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Discussion Starter · #325 ·
Nice Work Duncan. Looks quick on a tight course. I've probably mentioned it before but bang for buck I love Nankang AR1 for a light car. Apparently they aren't so good on a heavier car.
Just picked up the tyres - haven't paid for them yet!
They are "NEXEN"
I could not get "NITTO" in the right size and the local expert said these were good
Now I have the 225/45/17 Nitto - to go on the front - and the 235/45/17 Nexen - for the rear
These are asymmetric - I need to put the correct wheel and tyre on the correct corner

Will see how grippy the new rear tyres are at our drags on the 21st February
 

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Discussion Starter · #326 ·
Hi Guys
Last Sunday we had our annual 1/8th mile drag race

Did not do as well as before - possibly the tyres were too new!

A Hybrid 4WD Porsche was there to beat me - and he did!

My best time was 7.94 seconds and 96 mph (last year I got 7.83 seconds and 96 mph)
The Porsche got 7.88 seconds and 93 mph

I set up my cheapo GoPro knock off to look at my instruments - interesting




121946


"Series 3" was my fourth run - I spun the tyres and had to lift - that was half a second slower than the third run !!

My very first run I set the camera incorrectly - AND I spun the tyres half of the way down the strip and nearly went into the ditch

The "error bars" on those readings are quite large - just me taking the numbers from the videos

I seem to have increasing SAG until the controller maxes out at about 100 kph - only 20% - I was expecting more! - then steady away for 2 or 3 seconds before I lift
 

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Discussion Starter · #327 ·
Grass event today
Our fourth attempt at running our Christmas autocross and barbeque - the weather gods vetoed the previous three goes

Great fun
The grass remained a bit slippery but I had a great time





Running at 40% power - and I was nowhere near full throttle
 

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Discussion Starter · #328 ·
Another day out at Teretonga - reminded me of Scotland it rained on and off and I got wet





I have the new NEXEN's on the back and the NITTOS on the front - made a HUGE difference the car just felt so much more "planted"
And I moved from the back quarter of the results to the front quarter

Question
Spring Rates
I'm running
100 lb/inch on the front which give me wheel frequency of 100 CPM
125 lb/inch on the rear which give me wheel frequency of 94 CPM

With the amount of roll I'm getting (damn all) I'm thinking of changing to

70 lb/inch on the front which give me wheel frequency of 78 CPM
100 lb/inch on the rear which give me wheel frequency of 84 CPM

Comments??
 

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Another day out at Teretonga - reminded me of Scotland it rained on and off and I got wet





I have the new NEXEN's on the back and the NITTOS on the front - made a HUGE difference the car just felt so much more "planted"
And I moved from the back quarter of the results to the front quarter

Question
Spring Rates
I'm running
100 lb/inch on the front which give me wheel frequency of 100 CPM
125 lb/inch on the rear which give me wheel frequency of 94 CPM

With the amount of roll I'm getting (damn all) I'm thinking of changing to

70 lb/inch on the front which give me wheel frequency of 78 CPM
100 lb/inch on the rear which give me wheel frequency of 84 CPM

Comments??
It's always a trade-off. More suspension travel can allow the alignment to change. More suspension travel can allow the tires to continue gripping with dynamic weight transfer. After watching a few of your runs, I'd say try softer and see if it matches your style of driving (and what happens to the times). Especially during the slaloms, I could see potential gains by allowing more
movement.
 

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Discussion Starter · #330 ·
On Saturday I took my Device to a 1/4 mile drag strip
Could not stop the tyres spinning at the start - their rules would not let me do a burnout
Bit disappointing - managed 13.45 seconds and 104 mph
Acceleration is definitely dropping off!
It takes 7.9 seconds and 1/8th mile to get to 96 mph - the next 5 seconds and 1/8th mile only add another 8 mph

Note this is the European/Kiwi style - we do not allow the 1 ft run up that seems to be allowed in the USA
 

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On Saturday I took my Device to a 1/4 mile drag strip
Could not stop the tyres spinning at the start - their rules would not let me do a burnout
Bit disappointing - managed 13.45 seconds and 104 mph
Acceleration is definitely dropping off!
It takes 7.9 seconds and 1/8th mile to get to 96 mph - the next 5 seconds and 1/8th mile only add another 8 mph
It's not just the slow acceleration in the second 1/8th that hurts: if you had hit the 1/8th at your usual 96 MPH and continued up to 104 MPH at constant acceleration, it would have taken only another 4.5 seconds for the second 1/8th (for a total of 12.4 seconds if the first 1/8th took 7.9 s), so presumably in this run the first 1/8th wasn't that fast due to the launch traction issue.
 

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On Saturday I took my Device to a 1/4 mile drag strip
Could not stop the tyres spinning at the start - their rules would not let me do a burnout
Bit disappointing - managed 13.45 seconds and 104 mph
Acceleration is definitely dropping off!
It takes 7.9 seconds and 1/8th mile to get to 96 mph - the next 5 seconds and 1/8th mile only add another 8 mph

Note this is the European/Kiwi style - we do not allow the 1 ft run up that seems to be allowed in the USA
Hi Duncan, I've personally never drag raced so I don't have experience with the rules but I've never been to a drag racing event that didn't allow a tire "warm-up" (burn out),.. In fact I'd say it seems like it's encouraged here in Oz at least.

Every hillclimb event I've ever raced in has always allowed a "single continuous forward moving tire warm-up" strictly within a set portion of the pre-start-line area. (Prior to getting to start line).

Was this rule applied to your vehicle only? Or was nobody allowed to warm-up tires pre run?

Thanks for sharing your Motorsport with us, helping us all stay motivated back in the garage. Cheers.
 

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Discussion Starter · #333 ·
Hi Duncan, I've personally never drag raced so I don't have experience with the rules but I've never been to a drag racing event that didn't allow a tire "warm-up" (burn out),.. In fact I'd say it seems like it's encouraged here in Oz at least.

Every hillclimb event I've ever raced in has always allowed a "single continuous forward moving tire warm-up" strictly within a set portion of the pre-start-line area. (Prior to getting to start line).

Was this rule applied to your vehicle only? Or was nobody allowed to warm-up tires pre run?

Thanks for sharing your Motorsport with us, helping us all stay motivated back in the garage. Cheers.
I do a burn out at our annual 1/8th mile drags
But this was with a different motor club and their rules are
(1) Only their club members get to do a burnout
(2) Only cars that do less than 12 seconds get to do a burnout

So no burn-out for me!
 

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Discussion Starter · #334 ·
On Saturday I did a "Bent Sprint" at Teretonga

That is a higher speed event and I needed to get an actual speed license
Great Fun
I was not that quick ended up 13th out of 16!!

I moved my camera downwards to try and see the speeds - not a great success but you can see sometimes -
Straight up and down is 100 kph


Still with the existing springs - I have a softer pair but not fitted them yet

The four full power runs ate my charge - not enough for a fifth run and the fourth run was slightly speed limited
 

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Discussion Starter · #335 ·
Spring is here - So I got an Autocross at Teretonga!

I have reduced my spring rates
Replaced the 100 lb/inch on the front with 80 ib/inch and put the 100 lb/inch on the back in place of the 125 lb/inch
And it felt GOOD!

I failed to get the video running on my first three runs -
shame as I got out of shape on one corner on the first run and then had a full spin on that corner on the next run - but no video!

 

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Great work Duncan. The uneducated think stiff suspension is a good thing. It does have it's positives but for grip softer is often better. Role some of the weight onto the outside tyres and let em do most of the work.
 

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Role some of the weight onto the outside tyres and let em do most of the work.
Body roll doesn't affect load distribution between inside and outside tires unless the centre of mass shifts (typically upward with jacking or outward due to a low roll centre). Whatever the amount of roll, in steady-state cornering the moment due to the track width and different in contact patch force must equal the moment due to the centre of mass height and the product of vehicle mass and lateral acceleration.

I agree that excessively stiff is bad for traction.
 

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Discussion Starter · #338 ·
Body roll doesn't affect load distribution between inside and outside tires unless the centre of mass shifts (typically upward with jacking or outward due to a low roll centre). Whatever the amount of roll, in steady-state cornering the moment due to the track width and different in contact patch force must equal the moment due to the centre of mass height and the product of vehicle mass and lateral acceleration.

I agree that excessively stiff is bad for traction.
I would go further
"jacking" where the roll makes the center of mass higher will have an effect
The "roll center" will have zero effect - !
 

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I would go further
"jacking" where the roll makes the center of mass higher will have an effect
I covered that:
Body roll doesn't affect load distribution between inside and outside tires unless the centre of mass shifts (typically upward with jacking ...
The centre of mass can also rise (or fall) due to dive or squat resulting from deceleration or acceleration.


The "roll center" will have zero effect - !
I won't try to explain the roll centre in this thread, because the rest of the automotive world understands it.
 
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