Bell crank bushes and front damper works

corazon

Well-Known Member
#21
Nice, have you driven the car since fitting?
The 3mm isn't all that satisfying to look at is it, what kind of force do you reckon will be on it?
I'm thinking perhaps another 3mm under the joint attaching to the top one to form a shackle. You could weld a threaded spacer block between them for the rod.
Did you ever see Simon's welded versions?
 

cobraboy

Well-Known Member
#22
No Jim, not driven yet.
In making a shackle I think it will put the bar too close to the tyre, the pics are taken at full droop, the bar gets closer under compression.
TBH I am not as concerned with beauty as I am with a solution to a problem here.
I am convinced the force is one of extension onto the bar, if it breaks the 3mm I will think again, I bet it wont !

I am not on FB or whatever Simon is on, shame he no longer posts on here.
 

cobraboy

Well-Known Member
#23
First test run out, conditions far from ideal, cold weather, cold tyres, damp patches. Car behaved much better under braking, did not dart to the nearside, I think I am on the cusp of solving a problem that has dogged me since the build.
Adjustable front to rear brake bias valve is needed now to balance braking and then I think car will be coming together.
 

Gargo

Active Member
#24
Good good.
Interesting comment about the car darting under braking. Our car 'darts' on initial braking, during weight transfer. I've just accepted this as an effect of the wider, lower profile tyres on an uneven surface. Are you suggesting this reduces this on the car?

Can I ask if the 'first run out' was for both the Nylon and the top arm link fitted? I.e. Did you drive the car with only the Nylon fitted?
I ask as on first thoughts the braking loads would not be deforming the top mounts laterally, but again maybe they do. With the steering linking to the hub at the same point, any geometry deflection here will have an effect.

It's such a simple add-on.
 

cobraboy

Well-Known Member
#25
I did drive the car with nylon bushes only and the car pulled sharply left as before.
The run with the braces was brief, I had waited for the roads to dry and a storm was coming. Ten minutes after I got back it hammered down.
What I gleaned was the car pulled up much straighter, the effect from the braces was dramatic in the little time available to test.
The rear of the car is over braked, I either need to improve the front, or reduce the rear, when the car is balanced I can fine tune the front braces if they show any signs of flexing.
The top of the pillar moving around under braking is the cause of the darting issue. It cannot be moving in the solid pivot mounts so the bell crank arm itself must be flexing.
It is likely that I will have to make a set of modified lower arms with rod ends to eliminate movement there as well
I have now been lucky to have received info of two other designs of brace, so I may end up using elements of all three.
 
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cobraboy

Well-Known Member
#26
Dry and sunny here so..............
Road cold and tyres cold, so not really a fair test but, braking hard from 70 mph car was very controllable nothing like the wayward beast from before.
When at a walking pace stabbing the brake hard to pull the front down, before, the steering wheel would snatch left, now even not holding the wheel it stays straight.
Really gave the front suspension some abuse with the brakes, bouncing the car as hard and violently as possible in order to try and break the brace. Have examined it on return and cannot see any deformation or cracking of paint.
I need to make another video of the near side front wheel under braking to see from the outside the results, I have one of the original set up.

So psssst glug glug it's beer o'clock here :)
 

sdibbers

Well-Known Member
#27
Interesting the brace had such a dramatic affect on braking stability. It certainly seems to zero in on deflection in the top control arm. Just as an aside, have to magnafluxed the arm to check for micro cracks? Doesn't sound like a good thing that its changed by this so much.
 

harveyp6

Well-Known Member
#28
I'm struggling to see how that extra link between the top balljoint nut and the nut on the end of the bellcrank can acheive anything unless the bellcrank itself is flexing and I doubt that. Those two points are fixed ends of the bellcrank and all the link does is triangulate it, which if it is having an effect, must mean the bellcrank is flexing between those two points. If the bush in the outer end of the bellcrank is flexing and moving backwards, or the bulkhead is moving backwards, the extra link will just go backwards with the bellcrank surely?
 

cobraboy

Well-Known Member
#29
I would prefer to think the bell crank is not flexing too, but I am afraid it looks like it is. I agree that if the whole bell crank assembly was moving on either its bushes or by twisting the firewall then the brace would be ineffective.

I agree Magnafluxing would be a good idea.
The difference with the brace is night and day.
Mal Clark has told me they flex and has pictures of a friends Rover on a rally stage with crazy camber angles due to flexing bell cranks.

Guys I am no expert, I just try stuff and see if it works, I have been battling this for what.. 2 years ? I am so grateful to those who have gone before and are generous with their knowledge.
 
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Demetris

Well-Known Member
#30
The area of the wheel at about 2 o'clock seems to go inward as the front turns out.
That certainly looks nasty, and in my opinion the forces during this test isn't anything great.
Perhaps there is a problem with this bell crank, as Steven suggests.
I am also wondering that if this is a typical behaviour of a bell crank, why it doesn't happen equally on the other side?
 

cobraboy

Well-Known Member
#31
The off side does exhibit toe out but to a much lesser degree.
I think the nearside is greater because once the tyre starts to turn it gets pulled further round by the road as it is out of line. And as there are more links in the steering and a weedy idler on the near side it all adds up to a wheel not as well supported as the off side.
 

Gargo

Active Member
#32
Boy, that's dramatic. This is great (discussing it, not the deflection). Please please please, keep trying stuff and keep us informed.

I've just watched this in Youtube using the newly found controls, comma and full stop.
The first (,) nudges you back a frame in the video. The second (.) nudges you forward one frame.

At 37secs:
You can see toe-out deflection starts before the car dips; therefore as the brakes are applied.
The deflection stops as the wheel stops rotating; i.e. as the brakes stop.
.
IMHO this confirms brake force is what is causing the deflection, this eliminates a geometry problem (bump steer).

Interestingly, if you look at the side-view at 10secs I think there is visible rearward movement of the wheel, relative to the arch, just as the air valve passes 9o'clock, until the wheel stops turning. If the top arm is deflecting laterally This could be as the wheel toes out the wheel is effectively moving backwards as it and the pillar rotate to cause the toe out. Blimmy, does that make sense....

Is the right-hand or offside wheel, doing the same thing?

G.
P.s. Put the audio on that other thread :D
 

harveyp6

Well-Known Member
#33
Boy, that's dramatic. This is great (discussing it, not the deflection). Please please please, keep trying stuff and keep us informed.


The first (,) nudges you back a frame in the video. The second (.) nudges you forward one frame.

At 37secs:
You can see toe-out deflection starts before the car dips; therefore as the brakes are applied.
The deflection stops as the wheel stops rotating; i.e. as the brakes stop.
.
IMHO this confirms brake force is what is causing the deflection, this eliminates a geometry problem (bump steer).

Interestingly, if you look at the side-view at 10secs I think there is visible rearward movement of the wheel, relative to the arch, just as the air valve passes 9o'clock, until the wheel stops turning. If the top arm is deflecting laterally This could be as the wheel toes out the wheel is effectively moving backwards as it and the pillar rotate to cause the toe out. Blimmy, does that make sense....
I had seen vids of this and didn't know about the frame by frame option, but I had always thought it was brake related rather than suspension movement related, the problem being that applying the brakes also makes the suspension dive, but if we agree it's brakes, then compressing the suspension without using the brakes (just by weighting the front) shouldn't cause the wheel to toe out, especially if the wheel is chocked in place to stop any rearward motion.
 

Gargo

Active Member
#34
I think Harvey may have it.....
or the bulkhead is moving
I've been under the car and if the top of the pillar deflects sideways then the steering geometry should not be affected. However fore-aft deflection will have an effect. You have stiffened the top arm, by attaching the outboard mount to the top of the pillar; which has reduced the effect.
I would have a look at the defection in the bulkhead, as Harvey has already suggested.
I think the addon link is putting more of the braking force into the outboard mount and thereby causing less deflection overall.

I believe you when you say the problem has improved, but I think it is fore aft deflection you should be chasing not lateral. Well probably both.

Different behavior one side to the other would point to play or a breakage. Maybe a cracked bulkhead?

g.
 

sdibbers

Well-Known Member
#35
Interestingly, if you look at the side-view at 10secs I think there is visible rearward movement of the wheel, relative to the arch, just as the air valve passes 9o'clock, until the wheel stops turning. If the top arm is deflecting laterally This could be as the wheel toes out the wheel is effectively moving backwards as it and the pillar rotate to cause the toe out. Blimmy, does that make sense....
I was thinking the same thing. WHat sort of bushes do you have on the lower control arms? The rearwards movement of the wheel would suggest that they could be deflecting, although you say the brace is mitigating the movement now. I'd be tempted to try one of the home crack detection kits on the bell crank, it worries me it was fixed by the brace.
 

cobraboy

Well-Known Member
#36
Ta for the forensic Gargo ;)
OK bump steer has been eliminated ! My long suffering senior management partner videoed the wheels from the front the other day, there were no dampers fitted and myself was stood on the slam panel bouncing the car throughout its suspension travel, there was zero deflection on the road wheels.
The OSF does deflect a little under braking as outlined previously.
Don't know what you mean about audio ?
Yes I think the wheel moves rearward in the arch hence the comment about putting rod ends on the inner ends of the lower arms.

Ta M
 

cobraboy

Well-Known Member
#37
I had seen vids of this and didn't know about the frame by frame option, but I had always thought it was brake related rather than suspension movement related, the problem being that applying the brakes also makes the suspension dive, but if we agree it's brakes, then compressing the suspension without using the brakes (just by weighting the front) shouldn't cause the wheel to toe out, especially if the wheel is chocked in place to stop any rearward motion.
H
During compressing the suspension without braking the wheels stay true.
 

cobraboy

Well-Known Member
#38
I was thinking the same thing. WHat sort of bushes do you have on the lower control arms? The rearwards movement of the wheel would suggest that they could be deflecting, although you say the brace is mitigating the movement now. I'd be tempted to try one of the home crack detection kits on the bell crank, it worries me it was fixed by the brace.
Steven
I went from OEM rubber to poly on those bushes and then quickly back to new OEM rubber.
The reason is the angle of the bush, particularly the rear strut arm. When loaded due the the angle of the bolt the arm can move rearward. When I fitted poly the arm did move rearward and started to chew up the shoulder on the poly bush ! so I went back to rubber.
I had previously made nylon bushes for those two arms, but alas they don't line up when you solid bush them.
So I thought OK I need compliance but I need to stop the strut arm walking sideward - I'll make a nylon buffer to sit between the arm and the chassis on the rearward side - - - made no difference at all !

BTW I had a full head of hair when I started this.

Favourite saying at work when things go to shoite.................. If it was easy they'd all be doing it !
 
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cobraboy

Well-Known Member
#39
OK so rather than crack test the original bell crank arms that I have been torturing recently I found some more, here they are all prepped and ready to go on.
Shame the weather is not Rover friendly now. Hopefully though this will be a major leap forward with these fitted and the new braces.
IMG_2123.JPG
 
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