took some material off
Discussion
Took some material of these,
don't know the english word.
saves weight on the front suspension.
What do you think...take more off?
[URL=http://img155.imageshack.us/i/149n.jpg/]
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And yes of course we did
"a technical analises at the university"
before starting
don't know the english word.
saves weight on the front suspension.
What do you think...take more off?
[URL=http://img155.imageshack.us/i/149n.jpg/]
[/URL]Uploaded with [URL=http://imageshack.us]ImageShack.us[/URL]
And yes of course we did
"a technical analises at the university"
before starting
Edited by donkeasy on Friday 25th June 21:23
738 driver said:
Having driven a couple of examples on UK minor roads (uneven) I thought the steering became quite nervous as speed increased. Hence the idea of gaining more precise authority by extending the arm's.......more appropriate than a larger steering wheel perhaps?
How much did you extend it by? could give the car bump steer though and make it more nervous although careful positioning of the rack could sort that.Must admit I never found mine nervous at high speed.
Still on with my own build so not carried out the mod as yet Andy.
Seems when you hit a bump/series of them at speed those big 18's want to do their own thing and point the car anywhere but straight! So the idea was to create a longer lever to help control them rather than the tyres controlling you.......make it a little more user friendly on uneven roads I suppose.
Seems when you hit a bump/series of them at speed those big 18's want to do their own thing and point the car anywhere but straight! So the idea was to create a longer lever to help control them rather than the tyres controlling you.......make it a little more user friendly on uneven roads I suppose.
YIIHAA said:
To have the effect you want you'd have to shorten the arms. Longer arms give a greater steering angle for a given steering wheel position.
Are you sure.... think Leverage.... Longer arm from centre of KPI means more rack movement for same steering angle on outside wheel, so easier to turn, but you end up with less lock and a bigger turning circle.Also as well as Bump steer (which can be dialed out with some time and effort), you are changing the Ackerman angle (Angle difference between inside and out-side wheels on turn in). I have no idea how that changes the feel of the car....
donkeasy said:
Took some material of these,
don't know the english word.
saves weight on the front suspension.
What do you think...take more off?
..........
And yes of course we did
"a technical analises at the university"
before starting
It worries me when someone takes an existing part, machines lumps out of it, claims to have done the analysis then asks "Should I take some more off".don't know the english word.
saves weight on the front suspension.
What do you think...take more off?
..........
And yes of course we did
"a technical analises at the university"
before starting
If the analysis was done properly (I don't know where you would find the correct base data to use) then the correct amount has been removed, no more, no less.
How much weight has actually been saved and what impact will it have on the vehicle performance.
Steve
I remember a similar discussion on these arms some time ago when aluminium replacement parts were proposed. I think the Ultima factory took a pretty dim view of it (rightly so too) as these are highly stressed items. I personally would be very careful modifying them in this way, as a failure here would result in a big accident...
I understand the calcs you could perform to work out normal stresses, but what would happen if you hit a curb at speed? Suddenly you are above normal steering loads and a failure could result.
I'm all in favour of modifying and improving things, but I would use high strength steel such an EN24 or titanium if I was doing this mod. As far as I am aware, the factory arms are mild steel, which has a yield of around 300MPa. A high strength steel (EN24 or S99) or titanium is around 1000 to 1200MPa, which would give you an extra reserve factor of 3-4.
Cheers
Mart
Edited to add:
Looking again at the pictures, I would also say that the strengthening web you have left would had been more effective if it was on the faces against and away from the hub (i.e. at 90 deg from where it is), as this is the direction of load. Did you perform an FEA analysis on the part during your calcs? Don't want to critisise, but again, this is a critical component.
I understand the calcs you could perform to work out normal stresses, but what would happen if you hit a curb at speed? Suddenly you are above normal steering loads and a failure could result.
I'm all in favour of modifying and improving things, but I would use high strength steel such an EN24 or titanium if I was doing this mod. As far as I am aware, the factory arms are mild steel, which has a yield of around 300MPa. A high strength steel (EN24 or S99) or titanium is around 1000 to 1200MPa, which would give you an extra reserve factor of 3-4.
Cheers
Mart
Edited to add:
Looking again at the pictures, I would also say that the strengthening web you have left would had been more effective if it was on the faces against and away from the hub (i.e. at 90 deg from where it is), as this is the direction of load. Did you perform an FEA analysis on the part during your calcs? Don't want to critisise, but again, this is a critical component.
Edited by Davrianman on Monday 28th June 00:35
I have been working with a small group of people to design a entry level race car.
Having just gone through the process of designing uprights from scratch for our race car, the biggest problem area we found was not outright strength of the upright. That was fairly easy to get right. The problem area that we have encountered was trying to achieve the required amount of stiffness in the steering arm.
Think of the car as a 300kg formula ford with some wings.
Test criteria
4g bump
2g acceleration/braking/lateral load
Less than 0.1 degrees of deflection at this load.
Like I said. Getting something stiff enough was the main problem.
http://www.racemagazine.com.au/index.php?option=co...
Ryan
Having just gone through the process of designing uprights from scratch for our race car, the biggest problem area we found was not outright strength of the upright. That was fairly easy to get right. The problem area that we have encountered was trying to achieve the required amount of stiffness in the steering arm.
Think of the car as a 300kg formula ford with some wings.
Test criteria
4g bump
2g acceleration/braking/lateral load
Less than 0.1 degrees of deflection at this load.
Like I said. Getting something stiff enough was the main problem.
http://www.racemagazine.com.au/index.php?option=co...
Ryan
thx for your concerns, and thoughts.
"Shall I take more off", is of course meant as a teaser.
In my opinion the part is, due to productioncosts,
left with too much material, so we all could affort the car, thx TED.
And of course I am over-engineering, because the part was okee.
As you know the thing is bolted on to the hub.
Between the bolts there was no problem, to take even more material off.
But I liked the way it looked now, so I stopped.
The other part/side, stikking out, is not made thinner.
Only took of the material, that did not bring much.
"Shall I take more off", is of course meant as a teaser.
In my opinion the part is, due to productioncosts,
left with too much material, so we all could affort the car, thx TED.
And of course I am over-engineering, because the part was okee.
As you know the thing is bolted on to the hub.
Between the bolts there was no problem, to take even more material off.
But I liked the way it looked now, so I stopped.
The other part/side, stikking out, is not made thinner.
Only took of the material, that did not bring much.
Edited by donkeasy on Monday 28th June 11:27
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