Sumo Front Suspension
Pete Gregory
with the front wishbones then I would like to know. First, the Transit
track rod end on the top wishbone is stopping the unweighted suspension
arms dropping fully down to the shocker limit, therefore, putting the
ball joint under too much stress( in my opinion- not Dens).
Second, the top wishbone with its increased castor
offset now catches the coil over spring and sits on that too when un
weighted.
Third, the bottom ball joint outer steel flange is
hard up against the brake disc even at 1 1/2 degrees of camber .(These
are correct Ford parts not Pilgrim supplied)
Forth, the top transit track rod end is only screwed
into the wishbone captive nut 3/4 the way in order to get the correct
camber attitude. Pilgrim advise me that 'it will be ok when the weight
of the engine is applied' as if the suspension never fully unweights
during driving!!!!!!! obviously they never drive over hump back bridges
in Sussex.
The only option now is to cut off the end of the lower ball joint to
stop disc foul, and to extend the top wish bone to clear the spring
whilst putting an angle on the captive nut to alleviate the stress on
the top ball joint
Any other contructive suggestions would be helpful
Cheers Pete
Andrew W. Macfadyen
your report of the makers statement about suspension never "unweighting" (by
which I take they mean going to full rebound) as it suggests a real lack of
any knowledge of vehicle dynamics. If it is any consolation the very few
cases of ball joints "popping" out I have encountered have always happened a
low speed.
The only suggestion I can make short of getting an engineers report and
putting it in the hands of a good lawyer is to fit shorter shocks; contact
Spax they should either be able to find something to suit or shorten a set
specially. I don't know the design of the top wishbones but you may have to
modify them or fabricate new ones which clear the spring. The reduced castor
angle shouldn't be too much of a problem as long as you use radial tyres on
wheels without excessive offset.
It may be easier to fabricate a new wishbone rather than re-model the
existing one, you seem fairly clued up but if you need advice on the design
of the welds or other design matters I would be willing to help .
Andrew W. MacFadyen
B.Eng.Hon Mech. Eng.
Nick Cooper
the car and no problems until MOT needed doing. The front wheels on both
sides have worn through the inner wings on the back of the arches... Its
wearing thru when hard braking / cornering with a lot of lock.... I've heard
of early cortina suspension kits when braking hard, catching the sump on the
floor.
As an aside, check out my Cobra site at:
http://ds.dial.pipex.com/town/lane/xkn82/index.shtml
Cheers
Nick Cooper
John Rutter
<pe...@osscon.demon.co.uk> writes
...first three points snipped...
> Forth, the top transit track rod end is only screwed
>into the wishbone captive nut 3/4 the way in order to get the correct
>camber attitude. Pilgrim advise me that 'it will be ok when the weight
>of the engine is applied' as if the suspension never fully unweights
>during driving!!!!!!! obviously they never drive over hump back bridges
I thought a general rule for determining how much thread should be
engaged on components such as this was 'one-and-half-times-diameter', so
a 12mm diameter bolt should be engaged for 18mm thread length.
Must say, your description of the 'engineering' on this kit does much to
back up a lot of general opinions of these particular kits. I hope they
are not really as bad as some people would have you believe...
--
John Rutter, a.k.a. "Rut The Nut", J...@mconsult.demon.co.uk
Racing a Hawk HF3000 Stratos Replica kit car, see http://www.olb.co.uk
Follow the Auto Italia series on the Granada 'Men and Motors'
cable/satellite TV programme. midnight on Thursdays.
Andrew W. Macfadyen
stops, it years since I worked on a Cortina front suspension but I seem to
remember the bumpstops are long and soft it should be possible to fabricate a
block which lowers them . Spax also make a selection bumps stops designed to
fit on to the shock absorber piston rod but these can only be fitted to certain
types of damper.
I would also advise fitting shorter but stiffer springs all round as the
suspension should never bottom out durring normal braking and cornering. The
steering lock could also be restricted if required by the simple method used by
Chapman on the baby Elan --- fitting a collar at each end of the rack but this
would require machine shop facilities to turn the parts to the correct dia.
Andrew W. Macfadyen
PJ wrote:
> In article <35E26C29...@post.almac.co.uk>, Andrew W. Macfadyen
> <URL:mailto:am...@post.almac.co.uk> wrote:
> >
> > What you describe sounds highly dangerous, what is even more worrying is
> > your report of the makers statement about suspension never "unweighting"
> > (by which I take they mean going to full rebound) as it suggests a real
> > lack of any knowledge of vehicle dynamics.
>
> I don't think the maker did make a statement about the suspension never
> "unweighting" - they only implied something along those lines. Looking back
> at the notes I made (which are certainly not verbatim) shortly after I
> queried the front suspension design, I think they said something along the
> lines of 'such a situation doesn't arise "very often"'. Make your own mind up
> about the relevance of such a response, although for me, it would prompt the
> questions, "how often is 'not very often' in their mind, and what happens
> when it becomes too often?"
>
> > Andrew W. MacFadyen
> > B.Eng.Hon Mech. Eng.
>
> Den's very proud of his BSc...
>
> PJ.
> --
> _
> / \
> |___| Acorn RiscPC600 - StrongARM powered
> \___/
> \_|_
> \
Andrew W. Macfadyen
is in the reigion of 350 MPa ( about 52 Ksi) -- (ignoring bending stress and
stress concentration factors which will also contibute it) the normal yeild stress
for high strength steels for is taken as 340 MPa although drop forged steels can
go higher --- use a good quality TRE and you MIGHT just get away with it provided
the dampers are in good nick.
Pete Gregory
admit that I have never stripped one down. Im not quite sure which part of the ball
joint you were calculating but I seem to recall it almost impossible to calculate
shear strengths on unknown materials. These are NON FORD parts so I should imagine
that some poor family in asia Knocking these components out buy the ton in their
kitchen so I think in the trade it is termed as monkey metal.Thanks for your interest
and solutions. Im afraid I took the angle grinder to my wishbone tonight and inserted
new longer sections in. This I calculated would have to increase the O/A length of the
wishbone by a minimum of 19mm (which would also include packing shocker, top & bottom
wishbones backwards and forwards as required to get clearence). After putting a 5
degree crank on the captive nut in the end of the wishbone Ive cracked it!!!!! The TRE
is up to its maximum angle at full drop but not under stress, and ive got just enough
clearence over the shocker and the TRE screws in with even thread either side of the
nut showing. 6 hours work for just one side. Good job its bank holiday weekend coming
up!!! Now back to the powder coaters with them.
Gregs.
Sarclad International
Pete Gregory wrote in message <35E5E0E0...@osscon.demon.co.uk>...
>As far as I am aware, the ball is only swaged into the socket of the TRE
but i must
snip , snip,...
I have a Sierra based Sumo (1995 vintage) and haven't noticed the
problems mentioned with regard to top wishbones catching on springs
and bottom pivots contacting the disk rotors.
I have it on good authority that these problems occur with Ford Cortina
front
suspension in exactly the same circumstances i.e. when the suspension is
fully unloaded (full droop) albeit when heavy duty (estate?) springs are
used
- I would guess that Mr Designer at Ford didn't see it as a problem!
I haven't had the suspension on my Cobra reach full droop at all in 18
months
of driving and I guess it should only happen on extremely rare occasions
i.e. when taking hump back bridges far too fast! The damping generally slows
the takeoff of the car anyway - you will find more of a problem with the
suspension
bottoming (esp. at the back) when you land!
I had to dismantle a track rod end when I built my car (it is used to
regrind the
taper in the steering arm) and it really took some doing - I ended up sawing
off
all of the metal swaging - I am confident that they will only fail either
through faulty
manufacture or long after the rest of the car has fallen apart !
I am not sure that modifyng wishbones is a good idea unless you have
absolute
confidence in the guy welding them up.
Contact me if anybody wants any further info on the Sumo
Richard Alderton
co...@richald.force9.net
Andrew W. Macfadyen
which end the lock-nut is fitted but if you can taper it down with the angle grinder
towards the ball end it would reduce and stress concentrations the point on the threaded
shank of the TRE where it screws into the boss. --- in case like that taking metal away
from a sharp can make a component stronger.
P
Andrew W. Macfadyen
Sarclad International wrote:
> Pete Gregory wrote in message <35E5E0E0...@osscon.demon.co.uk>...
> >As far as I am aware, the ball is only swaged into the socket of the TRE
> but i must
>
> snip , snip,...
>
> I have a Sierra based Sumo (1995 vintage) and haven't noticed the
> problems mentioned with regard to top wishbones catching on springs
> and bottom pivots contacting the disk rotors.
>
> I have it on good authority that these problems occur with Ford Cortina
> front
> suspension in exactly the same circumstances i.e. when the suspension is
> fully unloaded (full droop) albeit when heavy duty (estate?) springs are
> used
>
The springs have nothing to do with it all MK3/4/5 Cortinas have long soft
springs which have a considerable pre-load, the suspension movement is limited
by the damper. In any case the Cortina top ball joint is designed for use in
wishbone and has a very large factor of safety -- its OK to use a TRE as a top
(i.e. not carrying spring loads) ball joint provided you take care to make sure
it is not carrying pullout loads. I have seen ball joints and track rods ends
pop out on a number of vehicles over the years.
Full drop situations occur quite frequently --- the B road I take travelling
home for example has several humps where a car will take off it is travelling
too fast, it frequently catches out strangers to the area.
Any problem on landing should be handled by the bump stops which is quite a
different can of worms, the correct way to check the bump stop setting is to
remove the springs and lower the car on to its wheels -- if any part of the car
touches the ground or fowls the tyres you have a problem.
The root problem is that the Cortina suspension is not the best base for a kit
car, but it is (was) just about the only double wishbone set up around in the
scrap yards so builders are forced to use it. The rear suspension is also
problematic on a Cortina donor , I had a friend who built a Cortina based
Spartan and encountered a large number of snags with the rear --- one can see
why often Jag rear ends are used.
As for modifying wishbones or making new ones it isn't a problem -- a
properly design top wishbone (i.e. one that isn't functioning as a suspension
stop) should only be subject to tensile and compressive stress -- if you want
to see just how little metal is required just look at Chapmans design for the
Elan (particularly the +2S).
With mild steel welded joints if properly designed and the correct size of rods
is used aren't a problem --- the key being if a slag inclusion or crack is
suspected you grind it out and start again.
David Lodge
>I had a friend who built a Cortina based
>Spartan and encountered a large number of snags with the rear --- one can see
>why often Jag rear ends are used.
Speaking as a Spartan owner, I've had some problems with the
suspension both front and read in terms of getting the right springs ,
shocks, void bush replacement thingys and the like, not to mention
bits of the kit getting in the way e.g. handbrake cables, exhaust pipe
etc.
Now the front of the car often (but not always) pulls to the left on
braking so I suspect that the front suspension rubbers have had it.
-------------------------------------------------------------------
#include<disclaimer.h> Opinions are mine and not those of Logica
David Lodge, DD Tel: +44 (0)171 446 4191
CommerciaL Evaluation Facility (CLEF), or: +44 (0)171 637 9111
Logica UK Ltd, Fax: +44 (0)1932 869119
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KT11 3LG http://public.logica.com/~lodged
John Rutter
<p...@tarags.demon.co.uk> writes
>> Must say, your description of the 'engineering' on this kit does much to
>> back up a lot of general opinions of these particular kits. I hope they
>> are not really as bad as some people would have you believe...
>
I have heard various people using derogatory terms such as 'cheap and
nasty' when describing these kits. Maybe 'cheap and cheerful' would be a
kinder description. After all, a lot of them have been sold so there is
a market for this level of car.
I'm not trying to get into a slagging-off match here, but would like to
know if there are any *real* problems with these kits, or if it is just
people being 'picky'. If things need to be improved, then owners should
eb able to pass feedback to the manufacturer in the hope that changes
will be made.
>
>
>> John Rutter, a.k.a. "Rut The Nut", J...@mconsult.demon.co.uk
>> Racing a Hawk HF3000 Stratos Replica kit car, see http://www.olb.co.uk
>
> Ahh, that was you in Autosport the other week was it? Started me thinking
>I'd like to have a go...
Yep, that was me (in the Orange car, number 77).
The Auto Italia series allows kits that use Italian donor cars
(engine/transmission), as well as the expected 'anything Italian'
classifications. Quite a variety in performance, with reverse grids used
to give the smaller cars a chance of higher finishing positions. At
Brands Hatch the other week I started 28th out of 29 cars. That meant
for a lot of overtaking to get to the front! I had a great time battling
with Chris Snowdon (the red Strat in the Autosport picture) and made it
up to third position - not that I knew that at the time. Then I half-
spun the car and Chris got by, with me finishing in fourth place
overall.
I certainly recommend this series, but only if your car is slower than
mine! Besides Stratos Replicas, there is a Minari being raced by Jim
Price. This car uses Alfa 33 donor parts. Of course, if you have the
cash to spare, you could go for a Ferrari Can Am replica. That would
probably be allowed by the organisers - certainly if it had an Italian
engine (Ferrari V8 being a reasonable choice, or perhaps a decent Alfa
V6). If someone would care to build me one of those, I could always race
it for you!!! ;-)
As per my sig below, the series is being televised on cable and
satellite. Trouble is, the programme production has lagged behind the
broadcast dates. This meant that the first programme was shown two weeks
in a row, and has been replaced for the last two weeks with rallying.
Not all bad from my view though, since I was interviewed in that first
programme and my car was given quite a lot of coverage :-)
I also notice that the programme preceding the (planned) Auto Italia
race is called 'Kits n Cruisin', on at 11:30 Thursday evenings. Seems
that most of the kit coverage there was filmed at Stoneleigh earlier in
the year. Details available on http://www.gsb.co.uk (if my memory is
working properly today).
I guess any further discussion on my antics, or TV coverage, deserves a
new thread - leaving this one for any further Sumo comments...
Regards,