Mushroom Inserts
Andybarbet - 2/1/05 at 07:04 PM
Apologies for sounding thick but what is the advantage of going for the mushroom inserts to fit the siearra front hub - with the offset hole for top
ball joint ? (Luego sell them offset)
A couple of places sell them with the hole in the centre and they are a lot cheaper, as they are easier to make.
I presumed it gave you more adjustment but read a thread somewhere saying there's no real advantage.
Cheers.....Andy
marc n - 2/1/05 at 07:37 PM
the ones with the holes off centre help with sva and also help dial out discrepancies in the sierra castings
regards
marc
DEAN C. - 2/1/05 at 08:00 PM
Marc is the expert but you really do need offset inserts.
This allows you to get equal castor angles on both sides.this allows for any variations in bracket mountings,ford castings and wishbone
tolerances,plus as Marc says you can put full castor(about 5 deg.) to give max "self centre" steering for SVA.
DEAN C. - 2/1/05 at 09:04 PM
Hi,after a conversation with Martin Keenan he has told me the main reason for the offset mushrooms is for the trailing angle,seeing as the hubs were
designed for macpherson struts and not wishbones.
This almost corrects the positioning of the hub,although he has said the hole ideally should be even nearer to the edge of the mushroom if it were
possible.
So you really do need them!
DEAN .........
gazza285 - 2/1/05 at 09:14 PM
It all depends on your top wishbones at the end of the day, if you are making your own the position of the top ball joint can be made to suit the
Sierra upright.
Mark Allanson - 2/1/05 at 09:49 PM
I am using Cortina uprights so it is really only a point of interest to me, but can someone explain this to me.
The castor angle will remain unchanged whichever position the insert is placed, all you will alter is the KPI, and the displacement of the stub axle
from the line between the upper and lower balljoints. Does this give you self centring? Does the migration of the axle line from the balljoints axis
alter the handling in an adverse way?
JoelP - 2/1/05 at 10:59 PM
apparently it contributes to self centering via drag, that the contact patch is behind the axis of steering. not sure quantitatively how much it
provides though.
gazza285 - 2/1/05 at 11:18 PM
It doesn't change the KPI either for the same reason it doesn't change castor.
Mark Allanson - 3/1/05 at 12:00 AM
quote:
Originally posted by gazza285
It doesn't change the KPI either for the same reason it doesn't change castor.
It obviously does affect the KPI, as you are changing the axis of the upper balljoint in relation to the lower one. Unless you only locate the insert
in the dead ahead or dead astern position. Any change in the insert to axis at 90° to the direction of travel will change the KPI
phelpsa - 3/1/05 at 12:03 AM
quote:
Originally posted by gazza285
It doesn't change the KPI either for the same reason it doesn't change castor.
I think your thinking that when the top moves to the right, the bottom moves to the left, which isn't true. If that was the case then the kpi
would dtay the same.
Adam
gazza285 - 3/1/05 at 12:24 AM
The top ball joint does not move as it is fixed to the top wishbone, not the upright.
The KPI is fixed wherever the offset mushroom is as the joint itself does not move.
Mark Allanson - 3/1/05 at 12:28 AM
quote:
Originally posted by gazza285
The top ball joint does not move as it is fixed to the top wishbone, not the upright.
The KPI is fixed wherever the offset mushroom is as the joint itself does not move.
If you alter the position of the insert at 90° to the direction of travel, this will alter the camber, and when you compensate for this, the top
balljoint will be altered in relation to the upper wishbone, thus changing the KPI
gazza285 - 3/1/05 at 12:33 AM
But the swivel point is in the same place! The swivel point is on the top wishbone, not the upright.
Mark Allanson - 3/1/05 at 12:39 AM
Yes, the swivell point is still on the upper wishbone, but it is in a differend place on the upper wishbone, due to the fact that you would have had
to wind in the top balljoint to get the camber right after moving the insert
[Edited on 3/1/05 by Mark Allanson]
gazza285 - 3/1/05 at 12:52 AM
But the KPI is a line between the centre of the top ball joint and the bottom ball joint. How can an offset mushroom move the swivel points? The
joints themselves do not move so the king pin inclination does not move either
Mark Allanson - 3/1/05 at 01:02 AM
quote:
Originally posted by gazza285
But the KPI is a line between the centre of the top ball joint and the bottom ball joint. How can an offset mushroom move the swivel points? The
joints themselves do not move so the king pin inclination does not move either
I am not explaining myself very clearly.
If the insert hole on the LH side was at the 9 O'clock position when viewed from behind, with the suspension fully set up, and then you moved it
to the 3 O'clock position, the camber would be changed by a factor of the distance between the offset of the balljoint hole from the centre of
the insert time 2.
To get your camber back to what it should be, you would have to wind in the upper balljoint back into the upper wishbone to compensate. The upper
balljoint would now be a few mm inboard from its previous position, but the lower balljoint would be unchanged, hence the change in KPI. The caster
would be unchanged
gazza285 - 3/1/05 at 01:04 AM
What you are saying is "when you compensate for this" I am saying "when you design proper wishbones for Sierra uprights"
gazza285 - 3/1/05 at 01:06 AM
Which I think was my original point
Mark Allanson - 3/1/05 at 01:08 AM
quote:
Originally posted by gazza285
What you are saying is "when you compensate for this" I am saying "when you design proper wishbones for Sierra uprights"
It doesn't matter what design upper wishbones you have, if you have offset inserts, and alter the position, you will have a change in camber,
which, when corrected will give a change in KPI
gazza285 - 3/1/05 at 01:19 AM
quote:
Originally posted by Mark Allanson
quote:
Originally posted by gazza285
What you are saying is "when you compensate for this" I am saying "when you design proper wishbones for Sierra uprights"
It doesn't matter what design upper wishbones you have, if you have offset inserts, and alter the position, you will have a change in camber,
which, when corrected will give a change in KPI
When corrected? Why not just make it right in the first place? Mark, I'm not having a go or anything, but why not get the wishbones right in the
first place. I know the Sierra uprights are not as geometrically correct as the Cortina ones, but it is only a slight modification to get them to
work.
[Edited on 3/1/05 by gazza285]
Mark Allanson - 3/1/05 at 01:29 AM
Jeez, I have the imprints of bricks on my forehead.
No welder in the world could make the wishbones so perfect that there would be no need for any post build suspension setup.
When you have finished your car, you need to fine tune the suspension, thats why it is adjustable.
If you use the offset inserts to adjust ANYTHING, your KPI will alter after you have corrected the camber change due to any alterations to the said
inserts.
gazza285 - 3/1/05 at 01:47 AM
"I am using Cortina uprights so it is really only a point of interest to me, but can someone explain this to me.
The castor angle will remain unchanged whichever position the insert is placed, all you will alter is the KPI, and the displacement of the stub axle
from the line between the upper and lower balljoints. Does this give you self centring? Does the migration of the axle line from the balljoints axis
alter the handling in an adverse way? "
This is what started me going in the first place
Rorty - 3/1/05 at 02:46 AM
I’ve attached a quick and crude drawing of a Sierra type “upright” with an offset type mushroom to illustrate the effects of rotating the mushroom.
The blue circle on the end of the stub axle represents the true camber and castor.
The pink circle on the end of the stub axle shows what happens when the hole in the mushroom is rotated towards the FRONT of the car by 2 degrees: the
stub axle moves towards the REAR of the car, thus increasing drag.
The red circle on the end of the stub axle shows what happens when the hole in the mushroom is rotated towards the wheel by 2 degrees: the stub axle
leans in at the top, thereby increasing negative camber.
The wishbones and balljoints have remained fixed throughout the procedure, therefore the KPI (the axis between the two balljoints) has not altered.
Only the scrub radius has changed in that plane.
The best option would be to install one of the mushrooms with a centrally located tapered hole and then design and fabricate (or purchase) the
wishbones to suit the geometry of the Sierra “upright”. Otherwise, any attempt to alter, say, camber, will result in unfavourable changes in other
areas.
What I didn't fully describe above, is the consequences of altering any changes to camber made by an offset type mushroom. Any attempt to CORRECT
mushroom-induced camber by altering the top balljoint position WOULD result in KPI changes.
[Edited on 3/1/05 by Rorty]
Rescued attachment camber-castor01.gif
DEAN C. - 3/1/05 at 10:51 PM
Phew! Glad thats cleared up then!
DONALD - 7/9/05 at 04:02 PM
Has any one used Escort McPherson struts on a Locost Build is so what are the pitfalls, at what lencth are theu cut off and what mushrooms are used?
DONALD - 7/9/05 at 04:03 PM
Has any one used Escort McPherson struts on a Locost Build is so what are the pitfalls, at what lencth are theu cut off and what mushrooms are used?
MikeRJ - 7/9/05 at 04:22 PM
I presume you mean the Mk1/Mk2 Escort upright?
The Mchperson strut is actually part of the upright, unlike the Sierra so you would have to devise some way of clamping a mushroom insert in after you
have chopped off the strut tube. It would be far simpler to use the cheap/readily available Sierra uprights (or if you can find a set, the Cortina
ones).
DONALD - 7/9/05 at 06:23 PM
What I was thinking of doing was to turning inserts like the mushrooms from steel and tap a thread in to then and welding them into place permanently.
This would mean a central hole and permanent position. The question is then what does this do to the geometry of the suspension?
britishtrident - 7/9/05 at 07:40 PM
quote:
Originally posted by DONALD
What I was thinking of doing was to turning inserts like the mushrooms from steel and tap a thread in to then and welding them into place permanently.
This would mean a central hole and permanent position. The question is then what does this do to the geometry of the suspension?
The geometry shouldn't be to bad but -
It would only work if you used a rose joint.
Alternatively you could make a threaded adaptor to take early Metro/Late Mini balljoints and make upper wishbone end from a Mini lower wishbone.
NS Dev - 7/9/05 at 08:18 PM
quote:
Originally posted by DONALD
What I was thinking of doing was to turning inserts like the mushrooms from steel and tap a thread in to then and welding them into place permanently.
This would mean a central hole and permanent position. The question is then what does this do to the geometry of the suspension?
Sylva cars did this for many years, but reamed out the adaptor with a tapered reamer to suit a transit draglink end like we use in the top of a
cortina upright.
NS Dev - 7/9/05 at 08:21 PM
quote:
Originally posted by Mark Allanson
quote:
Originally posted by gazza285
What you are saying is "when you compensate for this" I am saying "when you design proper wishbones for Sierra uprights"
It doesn't matter what design upper wishbones you have, if you have offset inserts, and alter the position, you will have a change in camber,
which, when corrected will give a change in KPI
CORRECT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
what the hell was this all about!!!! Jeeezus chriiiiiiiisssssst!
If you get in that much of a muddle for god's sake don't build a bloody car or you'll kill somebody!!!!
Sorry Mark, I know you were being more "restrained" in your answers!
JoelP - 7/9/05 at 09:20 PM
the point i always make, is that castor doesnt change, only the drag.
NS Dev - 8/9/05 at 07:02 AM
drag = kpi? I've never heard the term before?
JoelP - 8/9/05 at 05:53 PM
as far as i can remember, drag is a made up word to represent the distance from the contact patch centre to the centre of the steering axis, on the
ground.
how real an effect it is is open to debate.
NS Dev - 8/9/05 at 09:16 PM
ahhhhhhhhhh, now that's different again!!!
That is scrub radius!
Changes the kickback at the steering wheel and the self centreing to some degree, but is fixed by wheel offset, nowt to do with the top balljoint
really.
Main influence on scrub radius is wheel offset used.
MikeRJ - 8/9/05 at 09:21 PM
quote:
Originally posted by NS Dev
ahhhhhhhhhh, now that's different again!!!
That is scrub radius!
It is if you are talking about how far outside or inside of the wheel that the line falls. Joels "drag" is the distance between the contact
patch and the line in a longitudinal direction. This is affected both by castor angle, and by how far away from the center line the stub axle is
mounted (which is what the mushroom changes). Don't know what the correct term for it is, if any.
Triton - 9/9/05 at 07:17 AM
The mushrooms need to be fully cooked or allsorts of weird things happen...
Why nobody has made them like the head bearing/rake adjuster on "tricky" bikes i don't know.......or have i just sparked an idea again
and missed out or talking complete rubbish again
Peteff - 9/9/05 at 09:44 AM
These ones?
Rescued attachment tricky bike.jpg
JoelP - 9/9/05 at 05:43 PM
mike has it right, though obviously nsdev is correct about scrub radius too.
The best way to describe it is by comparing it to shopping trolley wheels, which obviously self centre because the steering pivot is far in front of
the centre of the wheel. I believe alan b has used the term drag in the past too, though he might've just been refering to a good night out
MikeRJ - 9/9/05 at 09:33 PM
quote:
Originally posted by JoelP
I believe alan b has used the term drag in the past too, though he might've just been refering to a good night out
Maybe a w/e job
