4 Pot Vented Disc Brake Kit
Discussion
Hi Bernard
They are early TR4 steering arms, part nos 127830 (RH) and 127831 (LH), according to my receipt. Shorter, which should quicken the rack slightly and also, more importantly for me, they raise the track rod and reduce the angle difference vs the suspension wishbones.
I have a spare one so here's some pics of the taper....
Shot alongside an original Taimar/3000M steering arm
Open end of taper - they're the same to my eye, but the close pic up makes it slightly less obvious
Other end of taper - again looks the same to my eye
Casting number - hard to read sadly with my bad eyesight
<added> Side comparison, for info - height change 1/2", length reduction 6" (turn centre to taper centre) down to to 4 1/2"
Hope these help. Rimmer Bros don't seem to have both sides available now, but @Adrian probably has them or similar if you need them
cheers
Nick
They are early TR4 steering arms, part nos 127830 (RH) and 127831 (LH), according to my receipt. Shorter, which should quicken the rack slightly and also, more importantly for me, they raise the track rod and reduce the angle difference vs the suspension wishbones.
I have a spare one so here's some pics of the taper....
Shot alongside an original Taimar/3000M steering arm
Open end of taper - they're the same to my eye, but the close pic up makes it slightly less obvious
Other end of taper - again looks the same to my eye
Casting number - hard to read sadly with my bad eyesight
<added> Side comparison, for info - height change 1/2", length reduction 6" (turn centre to taper centre) down to to 4 1/2"
Hope these help. Rimmer Bros don't seem to have both sides available now, but @Adrian probably has them or similar if you need them
cheers
Nick
Edited by status on Sunday 24th May 15:19
Its interesting to read all of this..
I was pretty sure that the Thurner chassis was noted for Bump steer and then Mike Bigland engineered it all out using a new chassis with TR6 uprights and careful geometry calcs???
I must have been mistaken!!
N
I was pretty sure that the Thurner chassis was noted for Bump steer and then Mike Bigland engineered it all out using a new chassis with TR6 uprights and careful geometry calcs???
I must have been mistaken!!
N
Edited by Dollyman1850 on Sunday 24th May 18:54
Dollyman1850 said:
Its interesting to read all of this..
I was pretty sure that the thornier chassis was noted for Bump steer and then Mike Bigland engineered it all out using a new chassis with TR6 uprights and careful geometry calks???
I must have been mistaken!!
N
That's interesting to hear, and I'm now going to go back and scrutinise my calculations thoroughly!I was pretty sure that the thornier chassis was noted for Bump steer and then Mike Bigland engineered it all out using a new chassis with TR6 uprights and careful geometry calks???
I must have been mistaken!!
N
All the reading I've done on suspension design and setup suggests that bump steer is something that should be minimised, and looking at the Taimar setup I can't see how that is the case. This seems to summarise reasonably well.
What I need is to have my car fully built up, to see the steering arm angles on the fully weighted car and take some more accurate measurements to confirm whether the arms I have bought are better or not.
If they're not an improvement then I'll be refitting the original arms again.
cheers
Nick
Here's a picture during rough set up, the chassis is set at the correct height to the floor (For my car) and the centres of the hubs are at centre of wheel heights.
It gives a better view of the angles the steering arms are at running height.
Please be advised, dont try this at home unless you have calibrated blocks of wood and ASME chalk lines.
It also shows the revised brake caliper bracket better, as per OP question.
It gives a better view of the angles the steering arms are at running height.
Please be advised, dont try this at home unless you have calibrated blocks of wood and ASME chalk lines.
It also shows the revised brake caliper bracket better, as per OP question.
Edited by GAjon on Tuesday 26th May 21:18
Slow M said:
status, thanks!
Neil, rumour has it, that when Triumph's supplies of the TR4 units dried up, the (ir)responsible person, for ordering parts stocks, at TVR, simply ordered the TR6 units, without consulting the chassis engineer.
Best regards,
Bernard.
Must be the same person changing the handbrakes Neil, rumour has it, that when Triumph's supplies of the TR4 units dried up, the (ir)responsible person, for ordering parts stocks, at TVR, simply ordered the TR6 units, without consulting the chassis engineer.
Best regards,
Bernard.
N
I would recommend making a gauge and testing bump steer if in doubt. I had a good book by Fred Puhn (http://www.amazon.co.uk/How-Make-your-Handle-HP46/dp/0912656468) which got me going on this topic many years ago.
My Griff was out by miles when I measured it, my rack was too high by default no idea whether that's normal for TVR.
Note that you need to care about - both the height of the rack - and the distance between the joints. Both have an effect and one cannot cure the effect of the other.
For bonus points you can adjust the Ackerman effect by moving the rack forward or backward.
My Griff was out by miles when I measured it, my rack was too high by default no idea whether that's normal for TVR.
Note that you need to care about - both the height of the rack - and the distance between the joints. Both have an effect and one cannot cure the effect of the other.
For bonus points you can adjust the Ackerman effect by moving the rack forward or backward.
kabaman said:
I would recommend making a gauge and testing bump steer if in doubt. I had a good book by Fred Puhn (http://www.amazon.co.uk/How-Make-your-Handle-HP46/dp/0912656468) which got me going on this topic many years ago.
My Griff was out by miles when I measured it, my rack was too high by default no idea whether that's normal for TVR.
Note that you need to care about - both the height of the rack - and the distance between the joints. Both have an effect and one cannot cure the effect of the other.
For bonus points you can adjust the Ackerman effect by moving the rack forward or backward.
The more I read, the more I notice, that people indicate, that Ackerman effect is not to be worried about, on racing cars. So, the more track oriented the toy is, the less you have to worry about it. My Griff was out by miles when I measured it, my rack was too high by default no idea whether that's normal for TVR.
Note that you need to care about - both the height of the rack - and the distance between the joints. Both have an effect and one cannot cure the effect of the other.
For bonus points you can adjust the Ackerman effect by moving the rack forward or backward.
Best regards,
Bernard.
I'll be honest I don't know how important ackerman is - and it's not easily adjustable/to experiment with by default.
You can think of it as affecting the radii of the two front wheel in relation to the arc the car wants to turn on (two arcs of front wheels). You can also think of it as adjustable toe in/out with turning the steering wheel, this dynamic case should have an effect on high speed stability even if it didn't change cornering.
The simplistic way I think of it is that at low speeds the slip angles of both tyres are zero so the ackerman should produce the idealised two arcs. At high speed the weight is on the outside tyre - the slip angle is much greater on that - so you want less ackerman (less inside wheel turning). So you need two different behaviors - at least for a road car.
If anyone has any info on this and recommendations based upon experimentation with an old TVR I'd love to hear.
N
You can think of it as affecting the radii of the two front wheel in relation to the arc the car wants to turn on (two arcs of front wheels). You can also think of it as adjustable toe in/out with turning the steering wheel, this dynamic case should have an effect on high speed stability even if it didn't change cornering.
The simplistic way I think of it is that at low speeds the slip angles of both tyres are zero so the ackerman should produce the idealised two arcs. At high speed the weight is on the outside tyre - the slip angle is much greater on that - so you want less ackerman (less inside wheel turning). So you need two different behaviors - at least for a road car.
If anyone has any info on this and recommendations based upon experimentation with an old TVR I'd love to hear.
N
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