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Author: Subject: scratch build exoskeleton thread
scudderfish

posted on 23/3/15 at 09:38 PM Reply With Quote
Why not just ditch the brake servo? I reckon most of the cars on here don't have one.
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peter030371

posted on 24/3/15 at 08:23 AM Reply With Quote
quote:
Originally posted by scudderfish
Why not just ditch the brake servo? I reckon most of the cars on here don't have one.


What he said

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drt

posted on 24/3/15 at 02:52 PM Reply With Quote
I can see your point(s)
:p

I had the argument with myself, and several people...
If you do not instal a servo you have 2 choices (obvious sorry)
1) huge travel and low (required) pedal force
2) huge pedal force and small travel
Even if you would vary the master cilinder piston diameter

I have a autograss buggy thing, and although it only weighs 390kg you really have to STOMP it
if you want some stopping power... so much so that I am not able to heel-toe in it.

I know most -if not all- kitcars,locost do not have a servo...
So hom much pedal force do you have to exercise ?

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peter030371

posted on 24/3/15 at 04:30 PM Reply With Quote
My previous experience of a non-servo'd Striker (circa 530Kg plus me and the passenger) over 18 years of use is that a firm pedal pressure is required but I could heel and toe and I could lock the wheels if i got a little carried away/ over excited on the track The feedback was very good without a servo and I would have hated to have lost that 'feel'.

My current Striker still has not got an engine or brake fluid so no idea if that is worse or better

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drt

posted on 24/3/15 at 06:37 PM Reply With Quote
Doing the maths comes up with 35.77Kg of foot pressure during 1G braking (idealized)
Sounds like a lot ?

piston diameter 0,048 m
Displacement brake pad 0,002 m
vehicle weight 500 kg
Braking 9,81 m/s^s
Braking torque, ideal brake distri, 1 wheel 927,936 Nm
Brake friction coeff 0,35
Saab 93 brake master cil bore 0,0238 m
pedal ratio 4,89
Mean brake disc radius 0,19 m
n number braking surfaces 2
Brake pad surface 0,005 m^2


Brake pad force 6976,962406 N
Pressure on brake piston 963904,5614 pascal (N/m^2)
force needed on master cilinder 1715,291053 N
Displaced volume brake caliper 3,61911E-06 m^3
Needed master cilinder displacement 0,813501871 cm
pedal displacement @ foot 3,97712026 cm
Pedal force @ master cilinder 174,8512796 kg
Pedal Force @ foot 35,76503446 Kg

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coozer

posted on 24/3/15 at 06:56 PM Reply With Quote
Good work, just a quickie, how you going to route gear cables, water pipes and whatever round the fuel tank? Over, under or to the side?

Are you running the water pipes down the centre? That's assuming the rads going to the front?

Steve





1972 V8 Jago

Midlana when I find the space...

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drt

posted on 24/3/15 at 07:26 PM Reply With Quote
quote:
Originally posted by coozer
Good work, just a quickie, how you going to route gear cables, water pipes and whatever round the fuel tank? Over, under or to the side?

Are you running the water pipes down the centre? That's assuming the rads going to the front?

Steve


Gear cables are going over, electrics to the side (away from exhaust) and water... wel
I was planning on sticking a rad in a pontoon... and the intercooler on the other side.
Thus choosing mass centralization over ideal weight distribution.

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scudderfish

posted on 24/3/15 at 07:38 PM Reply With Quote
quote:
Originally posted by drt
Doing the maths comes up with 35.77Kg of foot pressure during 1G braking (idealized)
Sounds like a lot ?

piston diameter 0,048 m
Displacement brake pad 0,002 m
vehicle weight 500 kg
Braking 9,81 m/s^s
Braking torque, ideal brake distri, 1 wheel 927,936 Nm
Brake friction coeff 0,35
Saab 93 brake master cil bore 0,0238 m
pedal ratio 4,89
Mean brake disc radius 0,19 m
n number braking surfaces 2
Brake pad surface 0,005 m^2


Brake pad force 6976,962406 N
Pressure on brake piston 963904,5614 pascal (N/m^2)
force needed on master cilinder 1715,291053 N
Displaced volume brake caliper 3,61911E-06 m^3
Needed master cilinder displacement 0,813501871 cm
pedal displacement @ foot 3,97712026 cm
Pedal force @ master cilinder 174,8512796 kg
Pedal Force @ foot 35,76503446 Kg


Assuming you weigh circa 70-80kg, that is about the force you feel on the sole of your foot when you are standing up.

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drt

posted on 24/3/15 at 07:51 PM Reply With Quote
Assuming you weigh circa 70-80kg, that is about the force you feel on the sole of your foot when you are standing up.


I'll take that as a very optimistic compliment ^^

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drt

posted on 27/3/15 at 11:53 AM Reply With Quote
So, I'm dumping the servo
thanks for the tips!

Now, this is the master servo.
How would you link that up? As the shaft does not describe a straight movement (due to pedal... etc etc you know)
A shaft with a 'spherical' end (ball) could work, but i'm scared about radial force on the plunger.
Because the saab converts the movement before the servo to straight (linear).


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peter030371

posted on 27/3/15 at 12:29 PM Reply With Quote
They normally have a clevis pin on the end but not sure how you would fit one to that master cylinder.
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drt

posted on 3/7/15 at 08:22 PM Reply With Quote
During these last months I have been busy with our uni's ecomarathon team pushing 700 hours since February... besides normal classes...
Not a lot of time for personal indulgences


Machining the brake shaft so it works without the servo


finished product


A lot more room now XD






In the meantime trying to get the molds done... this is the airscoop




And this the bottem of what is going to be the bonnet mold


An overview, Thinking of housing the rads and IC over there ... mass centralisation and shorter water/air lines


Because of my geometry, this is the only spot the rack could be in :s




Bonnet mold almost there


And a delivery of brake stuff

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drt

posted on 14/7/15 at 01:48 AM Reply With Quote
I've been waiting for news from RD for weeks
So, I'm doing detail work... front lights tonight





And the girlfriends car needs attention...

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drt

posted on 15/7/15 at 12:01 AM Reply With Quote
Today... a day of angry phone calls
...rear lights
...and setting up the rotaxmax for a week @ Spa (promised the misses 'spa' don't think she really gets it though XD)


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drt

posted on 11/8/15 at 11:13 AM Reply With Quote

So a whole week at the Spa Karting 25į-30įC and mostly dry.
Now she needs a top end rebuild, anyone knows somewhere I can get rotaxmax parts cheap ? Over here it's 500 smackeroonies... because you can only let it be done.


Build a small furnace... I got her up to over 1000įC, now i can cast my own ally parts.
First use was to make a ring for my girlfriend (had to make up for the Spa thing)... :p Silver is surprisingly easy to work with! and under the current raw silver price it was very cheap ^^


I have been waiting months for Rally design parts... really wondering if I would still place my orders there, the costumer service is a trainwreck.
Anyone having problems ?
To top it all I ran out of Argon, and over here all building sector and related companies are closed for a 3week builders holiday... no gas for me then.
Easing the pain with turning a gearknob



Thinking about using the Saab mirror glas in a DIY side mirror... because they are heated making life so much better when it's cold or starts to rain...
if they only weren't so vast.


Engine is in for the xxxxtime

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drt

posted on 11/8/15 at 11:25 AM Reply With Quote
Oh, I have been meaning to ask.
The original atom uses separate front parklights/daytimerunninglights...
Looking at the model they are crystalight ?
If so, they only sell reversing lights... who would be way too bright/diffuse to pass an iva :s
Anyone knows what they are ?

see->

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drt

posted on 11/1/16 at 11:16 PM Reply With Quote
It's been a while




testing the look in real life for the first time... before starting making the molds and ultimate products




vast amounts of resin, glass- and carbon weaves arriving along with corque sandwich material... postman sure loves me :p


sanding all the wood models for the last time before the varnish coat(seallent)


making parts for new steering arms... as the original ones had dreadful Ackermann, even without the change in wb and track




For a long time I was planning on using an LED as an reserve fuel warning light, just by adding resistors so that when the float reaches zero (aka lowest resistance) the power in the circuit would be +- 5v... a very simple, light and elegant solution... but turns out LED's aren't as picky as I thought... the lit up as soon as 1.5v getting ever brighter,
too bad... have to stick in a gauge


And then this disaster, I was planning on using the Saabs fuel pump as a piggy-back on my tank... turns out a Saab has just the one pump in the tank.
Thus it has internal passages to avoid air bubbles (it's a rotary pump, can't suck air) These are impossible to close of, so can't use the pump outside the tank... need to use the whole original plastic nightmare or buy a specific new one.
Keeping it locost by reworking the tank so to use the original.
This needs a bigger hole and bigger lowest fuel gathering compartment.



needed to go to, because of packaging the fuel nozzle is moving to the other side


To add to all that, I've just ordered jet cutted parts the week before; So I'll make the pump fitting the old fashioned way


The lid


the new set up, not very pleased with this


My tank is much higher than a Saab one, so this had to be lowered to

Now I'm waiting for some quite days to do all the composite work in one go

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drt

posted on 14/1/16 at 12:59 AM Reply With Quote
took her out to clean the hangar

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peter030371

posted on 14/1/16 at 08:11 AM Reply With Quote
Looking good, we have all sat in our chassis at some point and gone 'brum brum'
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drt

posted on 14/1/16 at 01:20 PM Reply With Quote


Getting very eager to get to do it for real

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jimmyjoebob

posted on 14/1/16 at 05:28 PM Reply With Quote
Build looks great - what make are the seats you are using and how much do they weigh?





If at first you don't succeed, hide all evidence you ever tried!

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drt

posted on 1/2/16 at 11:26 PM Reply With Quote
quote:
Originally posted by jimmyjoebob
Build looks great - what make are the seats you are using and how much do they weigh?



Sorry for the late reply.
I got the seats here;
,2 x BLACK BUCKET SEATS. PLASTIC 4x4 kitcar, beach buggy, Boat.
Very good service ! very good seats... I must warn that they are BIG...
much much bigger than the GFRP's I had (kitspares type ones).
But fit me very nicely !
But you'll need some space in your vehicle.
I didn't weigh them yet, the fabricator states 7.5kg a pop.

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drt

posted on 17/2/16 at 12:20 AM Reply With Quote

repositioned the gear selector again, somewhat higher and more back... much more ergonomic and now with a tiny throw


postman came by


I couldn't help myself XD


love the sound dampening qualities


I don't believe you guys have this in the uk ? Cheap as chips! and works so good... it could strip the grease of a steam engine


the end of another late night


spot the pun... it was only a matter of time this washed up


After a lot of careful cutting and consulting the cad model...


exhaust completed... now only wait for 2 Vbands to come in and weld it all up

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drt

posted on 17/2/16 at 10:17 AM Reply With Quote
tips on how to polish the dull stainless pieces to suit the mirror finish of the damper, please do not hesitate
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drt

posted on 4/3/16 at 01:24 AM Reply With Quote

Who needs a lasercutter when you have a nice angle grinder








The new gearselector in place, I'll be adding some structure to it later to give it lateral stiffness... and remove the now obsolete parts

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