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suspension pushrod angle in plan view?


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#51 NeilR

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Posted 21 October 2014 - 12:35

agree on the testing. Mentioned this to Monash a few years ago - hard to have good performance if your driver does not know the car



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#52 RogerGraham

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Posted 21 October 2014 - 12:52

That's not so bad is it?  Seems like a good way to quickly learn an awful lot about CAD/FEA-versus-real-world (hopefully!).  Of course, it depends how much time they have overall.

 

Edit: this was in reply to kikiturbo2


Edited by RogerGraham, 21 October 2014 - 12:52.


#53 Fat Boy

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Posted 21 October 2014 - 16:22

In my opinion, the best way to learn a lot about FEA is to get a stack of 1/8" balsa wood and some Crazy glue. Make a scale model. Twist it. Glue a new 'tube' in. Twist it, again. Glue in a paper shear panel. Twist, again. You'll learn more in a couple hours than you will in days of FEA work.

 

The inclination of FSAE students to change things just for the sake of changing it is pretty astounding. They generally just want to make it 'theirs' as opposed to making it fast. That's really the biggest reason why FSAE isn't really racing. It's an engineering comptetition, but it's _a long way_ from racing. The kids don't understand that.

 

The funniest part of it is that if you ask nearly any team in the paddock what the balance of their car is, and they'll say understeer. Let's think about this. Most cars have the same tires front and rear. They usually come in about 40-45% front weight. They've got a wheelbase/track ratio of maybe 1.1 or so. These cars _are not_ understeering. They're just driven poorly. If these kids would learn how to drive, they would end up much, much more successful in the competition rather than redesigning the car. It's amazing they are so rudderless that they can't appreciate this.



#54 Kelpiecross

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Posted 22 October 2014 - 03:35


I think it would be interesting for the FSAE competition to be open to more people than just uni students. Maybe classes for professional builders of racing cars, car manufacturers, general public "amateur" builders and an "outright" class for the best car from all groups.
I am not too sure who would be most likely to win.

#55 gruntguru

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Posted 22 October 2014 - 06:13

Anything is possible with sufficient manpower and budget, but the world's top FSAE teams would be very hard to beat.



#56 NeilR

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Posted 22 October 2014 - 11:43

I agree, there are some very fine minds in the FSAE teams.

Fat Boy I'm not sure about crazy glue - never used it, but I have done exactly that with Balsa and a flexible glue from a hot glue gun. Was very helpful.


Edited by NeilR, 22 October 2014 - 11:43.


#57 Fat Boy

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Posted 22 October 2014 - 16:39

Hot glue works just as well.

 

There are many great minds in FSAE. There are _very few_ racers. Those two are not necessarily the same thing.



#58 kikiturbo2

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Posted 23 October 2014 - 00:07

I did not want to push this discussion into FSAE bashing.. :)  FSAE is not a pure racing competition but an engineering comp... however, your points are very valid.. and main one is that quite a lot of those young engineers will first think how to make things differently and only much later stop to think why it was allready done in a certain way.



#59 Greg Locock

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Posted 23 October 2014 - 01:02

If you look at the scoring for FSAE it is primarliy an engineering competition, the race-driver circuit-driving stuff is a fairly small component. 

 

Design Event150

Cost & Manufacturing Analysis Event100

Presentation Event75

Acceleration Event75

Skidpad Event50

Autocross Event150

Fuel Economy Event100

Endurance Event300

Total Points Possible1,000



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#60 kikiturbo2

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Posted 23 October 2014 - 01:37

oh, only about 57.5%... :)



#61 Greg Locock

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Posted 23 October 2014 - 01:51

It'd be fun to see a race driver doeing fuel consumption and endurance testing. We usually get housewives to do those!



#62 kikiturbo2

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Posted 23 October 2014 - 03:02

HA! I once took part in some tire launch for continental and had the pleasure of doing tire testing on a fully instrumented car... basically 3 different compounds with diffferent carcas construction on the same car... Now, the performnace/handling test was revealing and fun of course.. but I was shocked how difficult the fuel consumption test was... sticking to prescribed speeds on a winding road was tedious at best. :)  I see now why everyone is working on a driverless car.. :)



#63 Kelpiecross

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Posted 23 October 2014 - 03:26

Anything is possible with sufficient manpower and budget, but the world's top FSAE teams would be very hard to beat.


I suspect the finishing order probably usually would be: F1 (or similar) team, car company, "amateur" and them uni team.

#64 Fat Boy

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Posted 23 October 2014 - 04:15

It'd be fun to see a race driver doeing fuel consumption and endurance testing. We usually get housewives to do those!

 

You see a race drivers doing a fuel consumption runs during damned near every race you watch that involves pit stops. You may not realize it, but you're watching it and it's completely underappreciated. A really good driver can save nearly 10% on fuel consumption and lose no more than 1-1.5% lap time (depends on the track).



#65 gruntguru

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Posted 23 October 2014 - 06:51

I suspect the finishing order probably usually would be: F1 (or similar) team, car company, "amateur" and them uni team.

With identical manpower and budget and FSAE competition rules the amatuer and the car company would have no chance in their first year against an established top-line FSAE team. The car company would catch up with a couple of years experience and the amatuers wouldn't get there - ever.

 

Edit. Probably a bit hard on the car company.


Edited by gruntguru, 23 October 2014 - 06:53.


#66 silente

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Posted 23 October 2014 - 07:38

It could be interested to involve some of the people of this forum and of others (since some of you guys actively discuss also elsewhere) and try to at least design a FSAE car or something like Niels has done.

 

Take a set of rules, extimate a budget and start from there. It could be pretty exciting and very very good to learn.

 

I work since three years for a big OEM and i did for more than 8 years motorsport. But still, the period when i learned the most was the time i spent on FSAE. And, anyway, this experience has opened my mind: i was then able to approach projects and to tackle problems in a completely new way. This has allowed me to learn in a different way afterwards. I can say that today i know much more about race cars as when i have worked on them! :D

 

Sadly, at least as far as i have seen, there are only a few people in a FSAE team that could use the same approach during their FSAE experience. I myself started to do things differently only afterwards, building up on the experience i have had in the mean time. This is limiting teams potential a lot. FSAE guys too often think to be smarter than they really are!

 

Anyway, it could be cool to design a cheap race car using a proper engineering approach. it would take a lot of time and a lot of headaches, but could be an amazingly cool learning experience. I could offer my experience with CAD (I use Catia V5 now and i have always worked mainly in the chassis/suspension area, although i once have designed a complete car for a small company), multibody (Adams) and generic vehicle dynamics and vehicle dynamics simulation, including driving simulation (http://drracing.wordpress.com/).


Edited by silente, 23 October 2014 - 07:50.


#67 kikiturbo2

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Posted 23 October 2014 - 13:41

here is mine.. :)

 

lower-mounts.jpg

 

_MG_2248.jpg



#68 Fat Boy

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Posted 23 October 2014 - 16:05

A lot of racing _is_ just extended FSAE racing, at least in terms of the people. In the 80's and 90's the guys on the teams came up through Formula Ford (specifically English FFord) in the 60's and the 70's. It's the same thing going on now. 20-30 years ago, we were all racing FSAE. Europe was a little later to the party, but in 10 years it's be dominated by the old FSAE'ers. too.



#69 NeilR

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Posted 04 November 2014 - 12:03

Kiki it looks nice - better welding than mine. I went to the national hillclimb champs on the weekend to cover it for race magazine ... after seeing Malcolm Oastlers car I believe that I could use mine for an off-road buggy. His car will be around 100kg lighter than mine and uses a turbocharged hayabusa engine with twice the power! BTW he won.



#70 Kelpiecross

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Posted 05 November 2014 - 04:21


Surely not 100kg lighter? Is it spaceframe?

#71 kikiturbo2

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Posted 05 November 2014 - 22:22

Kiki it looks nice - better welding than mine. I went to the national hillclimb champs on the weekend to cover it for race magazine ... after seeing Malcolm Oastlers car I believe that I could use mine for an off-road buggy. His car will be around 100kg lighter than mine and uses a turbocharged hayabusa engine with twice the power! BTW he won.

 

Thanks Neil..

as for weight.. I too have overbuilt the chassis... for two reasons.. first I had some major ideas on high stiffness... so that dictated most of the things.. and also, I have no deathwish... so the structure is pretty major.. Having said that, everything else is done for maximum lightness so I am expecting a light car.. when I get some time to finish it..



#72 NeilR

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Posted 06 November 2014 - 07:33

Kiki what are you building it for?

Kelpie, yes 100kg is correct. Malcolm used a CF tub and spaceframe rear for an all up weight of around 230kg (maybe less). Tub weighed 25kg.



#73 kikiturbo2

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Posted 06 November 2014 - 09:51

what for? for fun I guess.. :)

 

Idea was to do a single seater Atom like car, lighter with no aero and maximum connection between driver and road.. minimal mass, minimal inertia..Target weight is 350 kg wet and from what I see it is realistic but we'll see..

 

To be used on trackdays although I might hillclimb it... I am not looking to be super competitive. First mistake I did was believing I could register it, so I designed the suspension to have road level of travel and steering angle... If anything the whole project is educational, I want to learn first hand how certain suspension geometry characteristics translate into driving feel and performance.



#74 NeilR

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Posted 06 November 2014 - 10:37

yes me too, hence the quickly adjustable suspension.



#75 Kelpiecross

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Posted 06 November 2014 - 12:55

Kiki what are you building it for?
Kelpie, yes 100kg is correct. Malcolm used a CF tub and spaceframe rear for an all up weight of around 230kg (maybe less). Tub weighed 25kg.


That really is light - some motorcycles weigh more than that. It would be interesting to see some photos of the chassis etc.

#76 RogerGraham

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Posted 06 November 2014 - 13:41

 

Idea was to do a single seater Atom like car, lighter with no aero and maximum connection between driver and road.. minimal mass, minimal inertia..

 

Cheapy, is that you?!



#77 kikiturbo2

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Posted 06 November 2014 - 14:11

No,... but I miss him too... :) (from the forums.. hahahaa )


Edited by kikiturbo2, 06 November 2014 - 14:11.


#78 gruntguru

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Posted 18 November 2014 - 03:02

That really is light - some motorcycles weigh more than that. It would be interesting to see some photos of the chassis etc.

 

FSAE cars have been as low as 120 kg (not legal I believe). Legal cars at 143kg (combustion) and 177kg (electric).

 

230kg including turbo Hyabusa is astonishing!



#79 Kelpiecross

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Posted 18 November 2014 - 10:10

FSAE cars have been as low as 120 kg (not legal I believe). Legal cars at 143kg (combustion) and 177kg (electric).
 
230kg including turbo Hyabusa is astonishing!


A standard Hayabusa 'bike weighs about 230kg - so the car weight is a bit astonishing.

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#80 Fat Boy

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Posted 18 November 2014 - 17:47

In the dark ages there was no minimum weight in FSAE. 120 kg is plausible for something that was little more than a race kart. I doubt if anything that light was every particularly successful, however. The game is not won by the lightest, but by the first to cross the finish line.



#81 gruntguru

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Posted 19 November 2014 - 07:21

The 177kg electric figure I quoted was for TU Delft which is one of the more successful teams in FSAE these days. Electric FSAE vehicles often trounce their combustion competition.

 

For some idea of the performance - ETH Zurich hods the world record for EV acceleration from 0 - 100kph.  1.785 seconds. (1.6g average)



#82 NeilR

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Posted 19 November 2014 - 21:11

This is Malcolm's car - please note the 230kg weight was not confirmed by him - I will contact him and check.

_DSC0341_zps7a68b7dd.jpg

_DSC0487_zps8e7f38ff.jpg


Edited by NeilR, 19 November 2014 - 21:11.


#83 desmo

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Posted 19 November 2014 - 22:03

Very, very neat.  Is the little green thing a diff? Love the simplicity of the monoshock and the apparent lack of radiators, which I guess are optional for a hillclimb event. I'd like to see more.



#84 kikiturbo2

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Posted 19 November 2014 - 22:13

the green thing is a CV... the little black thing above it is the diff.. :)

 

really nice car..



#85 NeilR

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Posted 07 December 2014 - 07:31

Front end coming together:

 

WP_20141205_005_zps4d90a179.jpg



#86 NeilR

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Posted 19 July 2015 - 11:20

Some feedback - realigning the rear dampers and rear suspension to go on:

20150717_121000_zpswxkwy9vw.jpg

20150717_120949_zpsu6vppq1z.jpg



#87 Lee Nicolle

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Posted 21 July 2015 - 06:10

A standard Hayabusa 'bike weighs about 230kg - so the car weight is a bit astonishing.

230 kg or lbs. Even in lbs that sounds heavy though including trans and drives maybe ok



#88 MatsNorway

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Posted 21 July 2015 - 09:08

The entire bike comes in at 230kg.. And it might not be a light bike by todays standard it still is decent for a 1300cc bike with 180bhp made for about 10 years ago?

 

The most aggressive motorbikes (Ducati Desmosedici RR) has up to 200hp and comes in at 170kg.



#89 carlt

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Posted 25 July 2015 - 20:41

Some feedback - realigning the rear dampers and rear suspension to go on:

20150717_121000_zpswxkwy9vw.jpg

20150717_120949_zpsu6vppq1z.jpg

Thats what I suggested as best compromise with what you've got, still think so , plenty ways to brace/feed loads from the crank pivot into chassis



#90 NeilR

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Posted 26 July 2015 - 11:04

I've raised the damper 30-40mm as I realised that it was too low - I had not taken into account compression of the damper to normal ride. I'm also a little confused with the kinematics of the bellcrank - I'd like a slight rising rate to help with the aero load. Also the longitudinal angle seems too low to worry about at this stage


Edited by NeilR, 26 July 2015 - 12:55.


#91 gruntguru

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Posted 26 July 2015 - 23:05

A good way to visualise lever ratios is to forget the angles - just imagine the axis of the pushrod or damper as it passes the axis of the bellcrank/rocker. The distance of closest approach (90 deg) is the effective lever arm at that moment. For rising rate you need this distance to be decreasing (pushrod) and/or increasing (damper).

 

It is probably stating the obvious to say that the former is achieved by being over-centre and the latter through being before centre. The degree of rising rate can be adjusted by rotating the rocker at ride height (extending the pushrod or damper whilst shortening the other) although this will disrupt any travel limits designed in eg damper limits.

 

Bump stops are a popular route to "rising rate" but not as progressive as "designed in" geometry.


Edited by gruntguru, 26 July 2015 - 23:06.


#92 desmo

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Posted 27 July 2015 - 02:13

I've noticed, just by looking, that F1 cars sometimes can have either rising or falling rates in their rocker ratios. This ignores 3rd spring/damper and ARB effects on wheel rates, but still I wouldn't just assume that one or the other was optimal.



#93 gruntguru

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Posted 27 July 2015 - 05:21

One would expect racecars with significant aero downforce (especially underbody aero) would benefit from rising rate in heave - better mechanical grip at low speed (soft rate) and tight control of ground clearance at high speed (high DF >> stiff rate)



#94 Lee Nicolle

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Posted 27 July 2015 - 08:13

It'd be fun to see a race driver doeing fuel consumption and endurance testing. We usually get housewives to do those!

A racer friend did Bridge Rock tyre testing for a couple of years. Several set course to be driven in a timely [and timed] manner. In various different models with different tyres, compounds and treads. Some did not make it!

I have seen him doing housework however,,, and his then wife racing!



#95 NeilR

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Posted 27 July 2015 - 10:37

At the new damper height the rocker angle is approx 15deg before perpendicular, so some rising rate. The bellcrank is an alloy block supported by bearings with bolted-on, laser-cut steel side plates. What I might do is male up a couple of side plates with fairly long (curved) slots, which will allow me to get the car on its wheels and quickly adjust the ratio of pushrod/damper movement. I have a lot of work coming up in the next 3-4 weeks and may not get to model it as I would like in that time.


Edited by NeilR, 27 July 2015 - 10:38.


#96 gruntguru

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Posted 27 July 2015 - 23:12

Sounds like a good idea.

Better still - model the upright/damper motion ratio - that is the one that really matters.



#97 NeilR

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Posted 29 July 2015 - 13:01

Yes, very true re upright/damper MR. Around 35-30 years ago Peter Hollinger made a hillclimb car that had separated the spring/damper - used a torsion bar. Clever idea.

 

 

 

e80a5e2b15753110849005f3490c3653.jpg



#98 NeilR

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Posted 03 August 2015 - 11:06

Starting point 1, with thanks to Steve Webb.

 

Social%20Climber%20rear%20susp_zps4hhrky

 

SC1%20wheel%20travel%20vs%20MR_zpsctj4mf

 

SC1%20wheel%20travel%20vs%20shock%20trav

 

SC1%20wheel%20travel%20vs%20stiffness_zp


Edited by NeilR, 03 August 2015 - 11:07.


#99 gruntguru

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Posted 04 August 2015 - 08:04

Looks like a starting point you could actually run with. The highest wheel rate is double the lowest and 60% higher than at static ride height.

 

One of the things limiting how far you can go with rising rate is the damping. Because the dampers are fixed at the same MR as the springs, and damping is (usually) non-linear (falling rate), it is possible to end up either over damped at static ride height or under-damped at full bump - should you go too far with kinematic rising rate.



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#100 NeilR

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Posted 04 August 2015 - 09:34

Thank you for that, I had wondered if that was the case for ages. Did not have much time to answer last time. So with the confirmation about over dampers at static and under at upper reaches of suspension travel, what are the factors that would influence the decision making to err towards one or the other? I imagine the % of the run spent at one condition e.g. if the majority of the run was high speed/large spring compression then you would focus on that and the opposite true. What if mixed...look at sector times and see where most time is lost? Handling feedback from driver?


Edited by NeilR, 06 August 2015 - 09:02.