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Post by mightylad on Jun 2, 2012 17:42:49 GMT
I have the standard rack as supplied with the kit im not sure but i think the quick rack just reduces the steering input to the wheels i.e. Less turns of the steering wheel/faster steering response, i wouldn't have thought it changes the steering rack body itself (just the pinoion).
Spacers would be my choice but till now the washers have done the job just fine!!
Either way once you get on the open road you'll notice if you have bump steer... It makes the car dart all over the place at speed...
Ol
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Post by Steve on Jun 2, 2012 22:18:57 GMT
Regards to the quickrack question earlier, it was the strain on the mountings by the gearing up of the steering, plus super sticky tyres. However, I need to remember the weight on the front is nothing compared to a front engined Sierra  Washers will suffice nicely then I raised the nose of the rocket just, and it looks much better regards to angles. I've also done some bump steer research on the web, but not really any the wiser. |
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Post by mightylad on Jun 3, 2012 10:39:23 GMT
Coolio... I know where your coming from re: bolt strain, but as you point out the car is very light nosed so should be ok.. I too did a little bit of googling on the subject and found the best demonstration of bump steer on a YouTube video.. Try here www.dragtimes.com/video-viewer.php?v=gKJAukSZRT0Couple of 'noddy' vids on here but its all good... The first/top vid nicely shows bump steer - the wheels toe out when the suspension is compressed - not good at 70mph! Ol |
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Post by Steve on Jun 3, 2012 12:32:03 GMT
Ol, I notice your in Cheshire, If your ever over this way, feel free to call over. I'm in Merseyside. As yet, I've not been out in a rocket it would be very interesting considering what I'm building. I'd return the favour with brews and some wide band data logging if u required it I also have alloy welding facilities |
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Post by mightylad on Jun 3, 2012 13:09:26 GMT
Sounds like a plan Steve, just need some better weather! Its pretty rubbish outside at the mo...  Ol |
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Post by kiwicanfly on Jun 4, 2012 8:51:22 GMT
Quite a few posts above questioning the position of the rack and it's effect on bump steer.
Has anyone got any firm dimensions that the rack should be set to in order to eliminate bump steer?
Also is bump steer checked as part of the IVA testing?
New Zealand is real fussy on this, without this being measured and all but eliminated the car doesn't get a pass for the road.
Looking at the two pictures a few posts back from Ol and Ned it looks to me that Ned has no spacers but his lower wishbone angles down and Ol's has spacers but his wishbone is parallel to the ground. I figure that if both lower wishbones were set the same they would both need (or not need) the same amount of spacers.
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Post by Steve on Jun 4, 2012 9:03:12 GMT
Bump steer isn't checked as part of the IVA, however, the car is driven by the tester, and he/she gets a general feel and checks for steering self centering by performing 5-10 mph tight turns and releasing the steering. The self centering is then observed.
If the car had major bump steer, and it would have to be stupid, then it would be observed at the time the inspector drove it.
What Ol may have stumbled upon is a tuning tip, from his experiences. As from what I have read, wikipedia etc, is that some tuners will purposely generate/reduce bump steer, as it also affects roll steer. Which may be an advantage for some drivers.
Just adding fuel to the fire ;/
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Post by kiwicanfly on Jun 5, 2012 0:20:30 GMT
Bump steer isn't checked as part of the IVA, however, the car is driven by the tester, and he/she gets a general feel and checks for steering self centering by performing 5-10 mph tight turns and releasing the steering. The self centering is then observed. My uderstanding is that bump steer results in the car self-steering in some way when it hits a bump. Can this therefore be detected by simply doing tight slow turns? |
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Post by Steve on Jun 5, 2012 8:24:27 GMT
Maybe I should of explained better. Bump steer is not tested for at IVA however, if during the slow speed driving test a car displayed handling characteristics that were deemed dangerous, then it may be investigated more in depth.
It would have to be bad bump steer and probably a badly built, self designed vehicle, as the test area is flat, and the effect would not show up.
I would not worry.
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Post by mattsmev on Jun 12, 2012 10:39:33 GMT
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Post by Steve on Jun 22, 2012 15:05:52 GMT
Link works fine bud, good info. Thanks |
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Post by kiwicanfly on Jun 29, 2012 3:05:12 GMT
I am well interested to see if anyone has any actual figures for bump-steer measurements.
I have been doing some extensive solid modelling on the front suspension and am quite suprised how minor variations affect this significantly.
I will post some results in the technical section, probably next week.
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Post by mightylad on Jul 9, 2012 15:50:22 GMT
No measurements sadly, but from my previous Google around some people go to extremes of setting the rack height (using <250micron shims!) so I can imagine how minor variations affect the system.. I may have just been lucky with my x8 M12 washers under each rack mount!
hmm, interesting!
Ol
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Post by Steve on Jul 9, 2012 17:43:58 GMT
I think I'll be taking a closer look when I set the geometry later in the year, I'd like it at ride height with all running gear first, then maybe a carefully placed jack, and loosing the front dampers for calculations. I think
Some large thin repair washers may sit nice under the rack, and be cost effective.
I'm watching the budget right now, as I have to sell some more ZVH parts and boost controllers before u buy anything else. ;(
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Post by Steve on Jul 22, 2012 9:13:19 GMT
Little update, the engine was removed from my old drag/race car yesterday and is now being converted to rocket fitment.
It's a brand new build, but has been in storage for the last few years, so it's going to have a check over.
Pics to follow when I'm test fitting with the mtx75 transmission.
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The mobile version is somewhat shocking, and always asking for me to buy proboards for the iphone:(
If there is only one event you take your car to this year then believe me this is the one to go to. 