stressy
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| posted on 17/3/04 at 08:59 AM |
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Weight of Dedion assy
This is a repeat of a post i put in running gear, apologies if this causes any confusion.
Having read a few posts on the whole live axle / de dion / irs topic i have a query. Has anybody managed to actually get weights of components to be
able to quantitatively compare them. How much heavier/lighter is dedion compared to live axle etc?
Cheers chaps.
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Surrey Dave
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| posted on 17/3/04 at 10:30 AM |
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Good Question
I have the live axle setup , and apart from the diff the axle casing is surprisingly light, i moved a Sierra back end out of my garage lastweek
(diff,shafts ,drums,backplates) and it all seemed very heavy, thats without a dedion tube , I would be interested in the figures, although the crucial
point as far as the car is concerned is unsprung wieght not just the total weight.
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craig1410
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| posted on 17/3/04 at 01:05 PM |
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Hi,
I have weighed the various components of my Sierra based de-dion setup but the figures are at home. I'll look them out tonight and report back
then.
Cheers,
Craig.
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dozracing
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| posted on 17/3/04 at 01:19 PM |
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The point really is the overall weight and unsprung mass trade off.
The IRS setup makes the chassis heavy as well as adding lots of moving components which all have weight.
The live axle (Escort) being shorter and having a little diff, if fairly light, but, it all has to move up and down (increased unsprung mass).
Crucially the over riding decision for us to move away from Escort components was availability.
De Dion axle is lighter (less unsprung) than a live axle, but the cars weight is probably up as the transimission system is longer and the diff for
sure is more of a monster unit than the escort. DeDion does need much in the way of structure on the chassis and as such makes the chassis lighter
than the IRS.
Overall we ended up thinking the DeDion was the best compromise all round. It has its arguable advantages/disadvantages over IRS in terms of
performance.
Its more genuine in my mind as its the Lotus 7 system and also used on the more modern Caterhams.
Kind regards,
Darren
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stressy
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| posted on 17/3/04 at 01:37 PM |
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alright guys, cheers for the responses.
I drive a live axled car and i know that the live axle part is quite light in comparison to the irs equipment and i agree with Dozracing that the key
advantage of de dion over irs is the achievable advantage of chassis specific stiffness,the very reason caterham use that design.
With respect to my car i have found that the % of unsprung being so high makes it difficult to correctly set the rear damping rate, causing issues in
road use local to me (rough as), Therefore my plan is to evolve a reduced unsprung mass system and i am tying to find out how much can be achieved
using the "common" ford derived parts as opposed to looking further afield. My gut feeling says dedion will increase the weight of mycar
but in order to see significant improvement ford parts may not be the way to go for reducng the % unsprung.
Cheers again and i will be very interested to see the figures for the sierra bits craig..
Chris
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NS Dev
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| posted on 28/3/04 at 11:50 AM |
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My opinion (for what it's worth) is that as Dozracing says, the principle of keeping the back wheels connected by something is not at all a bad
one, as it maintains good geometry at the rear. In fact, apart from unsprung weight, the live axle has much to commend it! But, the ratio of axle
weight to car weight does make the damping difficult, so personally in an ideal world I would use de-dion, as GTS do. It is the best compromise, being
no heavier than wishbone IRS, but keeping the benefits of a solid axle, while reducing unsprung weight dramatically.
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craig1410
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| posted on 28/3/04 at 12:08 PM |
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Hi,
Sorry I forgot all about posting the weights. Here are a whole bunch of weights which may be of interest:
Bare De-dion axle (MK Engineering design) = 11Kg
Sierra rear driveshafts (Lobro) with hubs and carriers = 24Kg's
Sierra Differential (Lobro type) = 27.5Kg
Rover LT77 Gearbox = 47Kg
Front suspension (Both wishbones, Cortina upright, disc, hub and GTS shock/spring unit) = 15Kg each side
Escort steering rack = 5Kg
Sierra steering rack = 5Kg
Sierra steering column = 5Kg
GTS rear shocker unit = 2Kg
Front cortina calipers = 9Kg per pair
My McSorley 7+4 chassis with 16swg steel floor and using 2mm thick tube and no other non-welded components = 69Kgs
The above weights were all taken by standing on bathroom scales holding onto the various components and subtracting my own weight. Accuracy is
probably around +/- 2 or 3 %.
Cheers,
Craig.
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Peteff
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| posted on 28/3/04 at 05:45 PM |
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Did you allow for your weight loss during the exercise caused by all the lifting and stepping on and off or did you weigh yourself before and after
and average it out? You ought to have videoed the process so you could release it as The Craig + Mcsorley Workout. Jane Fonda eat your heart out!!!
Lose weight and come out fitter and build a car in one easy (not) session. Money back or a free Hernia operation, consult your psychiatrist before
starting this program and remember your home may be at risk if you go out and leave the door open.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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craig1410
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| posted on 28/3/04 at 06:20 PM |
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Yes, I would have given you similar figures for the V8 engine but the bathroom scales have strangely stopped working!
It'll be interesting to see how the weight of my de-dion axle compares with the one from GTS. I'd guess it will be within a few Kg's
either way but I don't know what gauge metal GTS use.
The chassis was weighed at the front then the back by lifting it just a fraction off the axle stands each time. The individual weights were 41Kg rear
and 28Kg front. Now that the floor is fitted it is a bit more difficult to just lift it in the middle and walk around with it like I used to...
(making Brrmm Brmm noises of course!)
As you can see the diff, driveshafts, hubs and hub carriers are a very large proportion (82%) of the total "axle" weight. I can't
help wondering what scope there would be for someone to manufacture light weight versions of these components as I'm sure they will be
over-engineered for Locost use. It also demonstrates that you could probably make the de-dion axle assembly considerably stronger (and thus heavier),
if there was any doubt over its original integrity, without making the overall axle all that much heavier.
Cheers,
Craig.
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britishtrident
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| posted on 4/4/04 at 03:29 PM |
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Just to point out an Escort English axle is a good whack lighter than the Salsbury Escort type, the Cortina 2 litre has heavier shafts and tubes and
is a lot heavier still.
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stressy
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| posted on 4/4/04 at 05:04 PM |
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A while ago on the forum a capri rear loadin(salisbury?) type axle including brakes was quoted to weight 47kg. This is what i have in my car, fitted
with the 1600 small diameter drums. I weighed an escort front loading axle(mr timken i assume) from a 1600gt and it weighed a little under 50 kg also.
the capri axle of course doesnot have all the gubbins attached that the cortina does.
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