A Tribute to an Engineering Educator 'Thirty Years Building of a Laboratory'

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MECHANICS AND MECHANICAL ENGINEERING 151

A Tribute to an Engineering Educator

'Thirty Years Building of a Laboratory'

An Introduction by H. B. Pacejka and C. Bogerman

S i n c e h i s i n a u g u r a t i o n i n 1950 as p r o f e s s o r i n V e h i c l e E n g i n e e r i n g a t t h e D e l f t U n i v e r s i t y o f T e c h n o l o g y p r o f e s s o r Van E l d i k Thieme has d e v o t e d h i m s e l f t o s e t t i n g up a l a b o r a t o r y e q u i p p e d f o r r e s e a r c h i n v e h i c l e e n g i n e e r i n g . A l o n g w i t h t t i e s e developments and o f t e n due t o t h e i n t r o d u c t i o n o f n o v e l , sometimes u n i q u e a p p a r a t u s and t e s t i n g f a c i l i t i e s , new areas o f r e s e a r c h have been i n i t i a t e d and s t i m u l a t e d t h r o u g h h i s e f f o r t s . T h a t h i s a c t i v i t i e s were t y p i c a l l y ahead o f t i m e u s i n g up t o d a t e t e c h n o l o g y may be i l l u s t r a t e d w i t h h i s p a p e r : 'Research on m a s s - s p r i n g systems' p u b l i s h e d on t h e o c c a s i o n o f t h e 8 t h FISITA C o n f e r e n c e h e l d i n 1960 i n The Hague, t h e N e t h e r l a n d s .

S t a r t i n g under p r i m i t i v e c i r c u m s t a n c e s based on a l o n g h i s t o r y o f e d u c a t i o n i n r a i l w a y v e h i c l e e n g i n e e r i n g , n o t a b l y steam l o c o m o t i v e s . Van E l d i k Thieme soon expanded h i s area o f a c t i v i t i e s and i n c l u d e d t h e r a p i d l y g r o w i n g f i e l d o f r o a d v e h i c l e e n g i n e e r i n g .

T h i s s p e c i a l i s s u e o f t h e D e l f t P r o g r e s s R e p o r t a t t e m p t s t o p r o v i d e an i m p r e s s i o n r e p r e s e n t a t i v e f o r t h e work w h i c h l e d t o t h e p r e s e n t p o t e n t i a l i n knowledge and f a c i l i t i e s . A l a r g e number o f r e s e a r c h a s s o c i a t e s and s t u d e n t s p l a y e d an e s s e n t i a l r o l e i n v a r i o u s developments and p r o j e c t s . A l t h o u g h acknowledgement o f t h e i r e f f o r t w o u l d be i n p l a c e a t an o c c a s i o n l i k e t h e p r e s e n t one we w i l l n o t honour i n d i v i d u a l s b u t c o n s i d e r t h e achievements a r e s u l t o f a c o l l e c t i v e e f f o r t t h r o u g h t h e y e a r s . S u f f i c e i t t o say t h a t t h e a c t i v e encouragement and p e r s i s t a n t guidance o f Van E l d i k Thieme b o r e f r u i t f u l r e s u l t s .

T h i s i n t r o d u c t i o n i s i n p a r t i c u l a r d e v o t e d t o t h e l a b o r a t o r y ^s i t e x i s t s todöy w i t h t h e v a r i o u s p i e c e s o f equipment and w i t h t h e r e s e a r c h w h i c h c o u l d n o t and can n o t be c o n d u c t e d w i t h o u t t h e s e f a c i l i t i e s . The s\±isequent a r t i c l e s g i v e an a c c o u n t o f r e s e a r c h t o p i c s and i n n o v a t i v e developments r e p o r t e d by t h e p r e s e n t s c i e n t i f i c s t a f f .

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152 7 ( 1 9 8 2 ) DELFT PROGRESS REPORT

S i n c e t h e s t a r t o f a c t i v i t i e s i n t h e e a r l y f i f t i e s and t h e e s t a b l i s h m e n t o f t h e D e l f t V e h i c l e Research L a b o r a t o r y a t i t s p r e s e n t l o c a t i o n i n 1959 t h e judgement, a n a l y s i s and improvement o f v e h i c l e p e r f o r m a n c e c h a r a c t e r i s t i c s have become o f i n c r e a s i n g i m p o r t a n c e s p e c i f i c a l l y r e g a r d i n g dynamic p r o p e r t i e s , r o a d h o l d i n g , b r a k i n g , c o m f o r t , energy e f f i c i e n c y a l s o i n c o n n e c t i o n w i t h c o n s t r u c t i o n o f roads and r a i l w a y t r a c k s .

The l a b o r a t o r y t o o k up t h e c h a l l e n g e t o b u i l d up a p o t e n t i a l o f f a c i l i t i e s and knowledge making i t p o s s i b l e t o c o n d u c t b o t h t h e o r e t i c a l and e x p e r i m e n t a l r e s e a r c h w h i c h answer r e q u i r e m e n t s r e g a r d i n g c r e a t i v i t y , q u a l i t y and a p p l i c a b i l i t y , a t t h e same t i m e t r y i n g t o be u n i q u e i n i t s a c h i e v e m e n t s .

Over t h e y e a r s a g r e a t niimber o f r e s e a r c h p r o j e c t s i n t h e a r e a s m e n t i o n e d above have been c a r r i e d o u t f o r t h e advancement o f t h e s c i e n t i f i c s t a t e o f knowledge, f o r t h e p u r p o s e o f e d u c a t i o n and f o r t h e a s s i s t a n c e o f i n d u s t r y , s o c i e t y and g o v e r n m e n t a l a g e n c i e s .

Three a r e a s o f r e s e a r c h have emerged as t h e main themes o f i n t e r e s t i n w h i c h t h e l a b o r a t o r y i s a c t i v e l y engaged:

- A c t i v e v e h i c l e s a f e t y - V i b r a t i o n s and c o m f o r t - New v e h i c l e c o n f i g u r a t i o n s

The f i r s t and t h e second theme r e q u i r e d u t i l i z a t i o n o f t e s t s t a n d s and s p e c i a l equipment. An o u t l i n e w i l l now be g i v e n o f v a r i o u s i n s t a l l a t i o n s a v a i l a b l e and o f r e s e a r c h p r o j e c t s c o n d u c t e d i n c o n n e c t i o n w i t h t h e s e f a c i l i t i e s . R e f e r e n c e w i l l be made t o c o n t r i b u t i o n s p r e s e n t e d i n t h e r e m a i n d e r o f t h i s i s s u e when a p p r o p r i a t e .

The a r e a o f aotix>e vehloZe safety i n c l u d e s s t u d i e s i n v e h i c l e c o n t r o l i n l o n g i -t u d i n a l ( d r i v i n g , b r a k i n g ) and l a -t e r a l ( s -t e e r i n g ) d i r e c -t i o n s i n w h i c h -t h e human d r i v e r i s a c t i v e l y i n v o l v e d . I t has soon been r e c o g n i z e d t h a t t h e t y r e p l a y s an e s s e n t i a l r o l e because i t b a s i c a l l y c o n s t i t u t e s t h e s o l e component w h i c h g e n e r a t e s and t r a n s m i t s t h e f r i c t i o n a l f o r c e s n e c e s s a r y t o a c c e l e r a t e o r d e c e l e r a t e t h e v e h i c l e i n t h e d e s i r e d d i r e c t i o n o r t o w i t h s t a n d d i s t u r b i n g e x t e r n a l f o r c e s . For t h i s r e a s o n , t h e l a b o r a t o r y has p a i d c o n s i d e r a b l e a t t e n t i o n t o t h e s t u d y o f t y r e b e h a v i o u r . F o r t h e i n v e s t i g a t i o n s i t i s e s s e n t i a l t o have a v a i l a b l e e q u i p -ment c a p a b l e o f m e a s u r i n g f o r c e s and mo-ments g e n e r a t e d b y t h e p n e u m a t i c t y r e . A number o f l a b o r a t o r y t e s t i n g r i g s have been d e s i g n e d and c o n s t r u c t e d w h i c h p r o v i d e t h e p o s s i b i l i t y t o e x p e r i m e n t a l l y assess c h a r a c t e r i s t i c s , b o t h s t a t i o n a r y and dynamic, under w e l l c o n t r o l l e d l a b o r a t o r y c o n d i t i o n s .

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mounted i n a s l e d g e moving o v e r t h e t y r e t o be t e s t e d w h i c h i s l o a d e d a g a i n s t t h e g l a s s p l a t e and w h i c h i s s e t a t a g i v e n s l i p and p o s s i b l y a camber a n g l e .

F i g . 1 Slow s]peed tyve test stand

The t y r e t o t a l f o r c e s and moments a r e measured t h r o u g h a m e a s u r i n g hub e q u i p p e d w i t h s t r a i n gages. The d i s t r i b u t i o n o f t h e s e f o r c e s i n t h e c o n t a c t p a t c h can be measured w i t h t h e a i d o f s p e c i a l f o r c e t r a n s d u c e r s i n s e r t e d i n a s t e e l p l a t e mounted i n t h e same s l e d g e b e h i n d t h e g l a s s p l a t e . A v i e w t h r o u g h t h e g l a s s p l a t e f r o m above p r o v i d e s an e x c e l l e n t i m p r e s s i o n o f t h e s l i d i n g p r o c e s s w h i c h t a k e s p l a c e i n (a p a r t o f ) t h e c o n t a c t p a t c h o f t h e s l i p p i n g o r d r i f t i n g t y r e , t h e l a t t e r b e i n g b r o u g h t a b o u t t h r o u g h t h e a c t i o n o f a b r a k i n g c o u p l e o r b y s e t t i n g t h e t y r e a t a s l i p a n g l e .

I n v e s t i g a t i o n s a t h i g h e r speeds o f r i o n n i n g may be c a r r i e d o u t on t h e drum t e s t s t a n d . The two c o - a x i a l drums possess a d i a m e t e r o f 2.5 m and may r u n a t speeds as h i g h as 300 km/h. The p a i r o f drums a r e l a i d o u t t o s u i t i n v e s t i g a t i o n s on c o m p l e t e f r o n t o r r e a r a x l e s . The t e s t s t a n d was d e s i g n e d t o meet l o a d s and

speeds e n c o u n t e r e d when t e s t i n g a i r c r a f t l a n d i n g g e a r s . The m a j o r i t y o f e x p e r i m e n t s however, c o n c e r n e d t h e t e s t i n g o f t y r e s . A s p e c i a l l y d e s i g n e d r i g i s p l a c e d over one o f t h e drums ( F i g , 2 ) . W i t h t h i s r i g t h e o r i e n t a t i o n and l o a d i n g o f t h e t y r e i s c o n t r o l l e d . A g a i n t h e s t r a i n gage based m e a s u r i n g hub, d e s i g n e d b y l a b o r a t o r y s t a f f and f i r s t used i n 1966, p r o v i d e s t h e e l e c t r i c a l s i g n a l s o f f o r c e s and moments c r e a t e d t h r o u g h t h e v a r y i n g i n p u t m o t i o n o f t h e w h e e l , t h a t i s o f t h e r i g .

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15^+ 7 ( 1 9 8 2 ) DELFT PROGRESS REPORT

F i g . 2 High syeed dvwn test stand with tyve test rig

The r e s u l t o f t h e s e i n v e s t i g a t i o n s may be g i v e n i n t h e f o r m o f s o - c a l l e d t y r e c h a r a c t e r i s t i c s used f o r comparison between d i f f e r e n t t y r e makes o r t e s t con-d i t i o n s , b u t a l s o f o r s u p p l y i n g con-d a t a n e c e s s a r y i n t h e o r e t i c a l a n a l y s e s o f v e h i c l e c o r n e r i n g p e r f o r m a n c e and s t a b i l i t y p r o p e r t i e s . A d i s a d v a n t a g e o f u s i n g t h e driom t e s t s t a n d i s t h e f a c t t h a t t h e s u r f a c e i s c u r v e d . A l s o , t h e s u r f a c e m a t e r i a l i s s t e e l ( p o s s i b l y p r o v i d e d w i t h s p e c i a l s u r f a c e e l e m e n t s o r e.g. s a f e t y w a l k p a p e r ) and can o n l y be used under d r y c o n d i t i o n s . E s p e c i a l l y t h e l a t t e r r e s t r i c t i o n w i l l g i v e r i s e t o c o n s i d e r a b l e d i f f e r e n c e s w i t h r e s p e c t t o r e a l i s t i c c o n d i t i o n s met on t h e r o a d . F o r c o m p a r a t i v e e v a l u a t i o n o f b o t h r o a d t e x t u r e s and t y r e c o n s t r u c t i o n s and t r e a d d e p t h s b u t a l s o f o r t h e assessment o f r e a l i s t i c t y r e c h a r a c t e r i s t i c s used i n v e h i c l e dynamics s t u d i e s , t h e l a b o r a t o r y has t o i t s d i s p o s a l t h r e e t e s t v e h i c l e s . The f i r s t f a c i l i t y i s a t r a i l e r p r o v i d e d w i t h an i n s t r u m e n t e d , f u l l y a u t o m a t i s e d t e s t s e c t i o n f o r t h e t e s t i n g o f passenger c a r t y r e s and m o t o r - c y c l e t y r e s under b r a k i n g , s i d e s l i p and camber c o n d i t i o n s ( c f . F i g . 3 ) . Water may be s p r a y e d i n f r o n t o f t h e t e s t t y r e . The v e h i c l e i s l i m i t e d t o a speed o f 100 km/h. The second f a c i l i t y o f much s i m p l e r d e s i g n and w i t h l i m i t e d p o s s i b i l i t i e s i s t h e one-wheel t r a i l e r . T h i s t r a i l e r can accommodate a t r u c k t y r e f o r t h e measurement o f s k i d r e s i s t a n c e w h i l e b r a k i n g . F i g u r e 4 shows a t y p i c a l r e s u l t i n d i c a t i n g t h e maximum b r a k i n g f o r c e a t a r a t i o t o t h e wheel l o a d a t t a i n e d a t optimum wheel s l i p , and a t t h e r i g h t , t h e l o c k e d w h e e l v a l u e o f t h e same l o n g i t u d i n a l f o r c e a t 100% wheel s l i p , b o t h as a f u n c t i o n o f speed o f t r a v e l and f o r d i f f e r e n t v a l u e s o f t r e a d d e p t h . C o n s i d e r a b l e d i f f e r e n c e s between c a r t y r e s and t r u c k t y r e s show up.

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T MECHANICS AND M E C m N I C A L ENGINEERING 155

F i g . 3 Outdoor tyre testing trailer towed hy a truck

m m Omm 12mm -6 Omm 7 m m Omm 12mm Omm 20 AO 60 80 100 k m / h 0 20 40 60 80 10Ü k m / h

F i g . 4 Brake force ratios at optimum braking and at wheel look for oar-tyres

and for truck tyres at different tread depths

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156 7 Cl 982) DELFT PROGRESS REPORT

The t h i r d t y r e t e s t v e h i c l e i s based on a C i t r o e n Break. The two b a s i c i m p r o v e -ments on t h e o l d e r f a c i l i t i e s a r e : more compact, l i g h t w e i g h t and easy t o h a n d l e d e s i g n k e e p i n g a b r e a s t w i t h t h e l a t e s t developments i n t e c h n o l o g y and s e c o n d l y t h e p o s s i b i l i t y o f b e i n g a b l e t o c a r r y o u t t e s t s a t t y p i c a l highway speeds. F i g u r e 5 g i v e s t h e l a y - o u t o f t h i s f r o n t - w h e e l - d r i v e s t a t i o n c a r w h i c h has been m o d i f i e d so as t o house t h e m e a s u r i n g system. B e s i d e s t h e t e s t wheel a dummy wheel has been i n s t a l l e d i n t h e v e h i c l e . When m e a s u r i n g l a t e r a l f o r c e c h a r a c -t e r i s -t i c s , -t h i s dummy wheel compensa-tes -t h e s i d e f o r c e d e v e l o p e d b y -t h e -t e s -t w h e e l . The l a t e r a l s t a b i l i t y o f t h e v e h i c l e i s t h e r e b y p r e s e r v e d . The p r i m e f e a t u r e o f t h e m e a s u r i n g system i s a compact and l i g h t w e i g h t m e a s u r i n g hub based on p i e z o - e l e c t r i c a l f o r c e t r a n s d u c e r s . I n comparison w i t h t h e o l d e r much h e a v i e r hub based on s t r a i n gages t h i s new D e l f t development combines a c c u r a t e m e a s u r i n g and t e s t i n g a t d y n a m i c a l l y r e a l i s t i c c o n d i t i o n s .

The need f o r t y r e e x p e r i m e n t a l d a t a f o r t h e p u r p o s e o f t h e o r e t i c a l m o d e l l i n g o f v e h i c l e systems has been e x t e n d e d t o t h e dynamic p r o p e r t i e s o f t h e r o l l i n g and s l i p p i n g t y r e . The s t u d y o f s e l f - e x c i t e d wheel shimmy, f r o n t wheel v i b r a t i o n s i n d u c e d b y i m b a l a n c e , n o n - u n i f o r m i t i e s o f t h e t y r e and r o a d unevenness demanded dynamic t y r e t e s t i n g . For t h i s p u r p o s e p r o v i s i o n s have been made t o o s c i l l a t e t h e r i g w h i c h c o n t a i n s t h e m e a s u r i n g hvb w i t h t y r e r o l l i n g on t h e drum. The wheel can be o s c i l l a t e d a b o u t a v e r t i c a l a x i s up t o about 8 Hz. F o r c e and moment f r e q u e n c y r e s p o n s e c h a r a c t e r i s t i c s have been assessed and used i n t h e a n a l y s i s o f wheel s u s p e n s i o n and s t e e r i n g dynamics. A new l i g h t w e i g h t wheel o s c i l l a t i o n t e s t s t a n d f o r h i g h e r maximum t e s t f r e q u e n c i e s and c o m p l e t e a n t i - s y m m e t r i c e x c i t a t i o n c a p a b i l i t i e s i s b e i n g d e v e l o p e d . B e s i d e s , t h e s y m m e t r i c t y r e r e s p o n s e , i . e . t h e v e r t i c a l and f o r e and a f t f o r c e response t o v e r t i c a l wheel a x l e motions', wheel o u t o f roundness and roadunevenness i s needed. A s p e c i a l f a c i l i t y has been c o n s t r u c t e d a l s o e q u i p p e d w i t h p i e z o f o r c e t r a n s d u c e r s and c a p a b l e o f t e s t i n g t y r e s a t f r e q u e n c i e s up t o a b o u t 25 Hz. A l s o t h e s e symmetric response d a t a have been used f o r f r o n t wheel a n a l y s i s .

The a r t i c l e on r e s e a r c h i n t y r e m.echanics and v e h i c l e dynamics b y P a c e j k a g i v e s more i n f o r m a t i o n on t h e a p p l i c a t i o n o f e x p e r i m e n t a l response c h a r a c t e r i s t i c s i n t h e t h e o r e t i c a l m o d e l l i n g p r o c e s s .

I n t h e a r t i c l e "Recent developments i n t y r e t e s t i n g " b y Zwaan a d e t a i l e d t r e a t m e n t o f t h e n e w l y d e v e l o p e d m e a s u r i n g huh i n s t a l l e d i n t h e h i g h speed t y r e t e s t v e h i c l e and i n t h e o u t d o o r m o t o r c y c l e t y r e t e s t i n s t a l l a t i o n i s g i v e n .

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The a r t i c l e " S l i d i n g and r o l l i n g - f r i c t i o n o f t y r e - r o a d and w h e e l - r a i l c o n t a c t s " by Savkoor d e s c r i b e s f u n d a m e n t a l t h e o r e t i c a l and e x p e r i m e n t a l r e s e a r c h i n t y r e f r i c t i o n and s t i f f n e s s i n c l u d i n g a s p e c t s o f r a i l w a y w h e e l s .

Brakes and b r a k i n g p e r f o r m a n c e o f r o a d and r a i l v e h i c l e s c o n s t i t u t e a n o t h e r i m p o r t a n t a s p e c t o f r e s e a r c h i n a c t i v e s a f e t y . I n v e s t i g a t i o n s i n v o l v e e x p e r i m e n -t a l and -t h e o r e -t i c a l r e s e a r c h i n -t h e p r o p e r a c -t i o n o f -t h e b r a k e i -t s e l f (-tempera- (tempera-t u r e , wear, f r i c (tempera-t i o n , v i b r a (tempera-t i o n s ) and o f (tempera-t h e b r a k i n g p r o p e r (tempera-t i e s o f (tempera-t h e c o m p l e (tempera-t e v e h i c l e ( s t o p p i n g d i s t a n c e , d i r e c t i o n a l s t a b i l i t y ; a n t i - l o c k systems, b r a k e p r o p o r t i o n i n g , r e t a r d e r s ) . Three t e s t s t a n d s a r e a v a i l a b l e i n t h e l a b o r a t o r y f o r t h e e x p e r i m e n t a l t e s t i n g o f b r a k e s and o f v e h i c l e s ( t r u c k s ) d u r i n g b r a k i n g . ' Two o f t h e t e s t machines a r e c a p a b l e o f m e a s u r i n g t h e b e h a v i o u r o f an i n d i v i d u a l b r a k e and a r e d e s i g n e d as i n e r t i a dynamometers.

The s m a l l e s t one can h a n d l e b r a k e s o f t h e s i z e f o u n d on passenger c a r s and l i g h t 2 t r u c k s ( F i g . 6 ) . The maximum moment o f i n e r t i a o f t h e f l y w h e e l s i s 72.9 kgm and t h e maximum t o r q u e o f t h e t e s t b r a k e under s t o p t e s t c o n d i t i o n s comes t o 3920 Nm (400 k g f . m ) . VThen t e s t i n g a b r a k e on t h e machine t h e energy d i s s i p a t e d i s u s u a l l y made e q u a l t o t h a t d i s s i p a t e d b y t h e same b r a k e on t h e v e h i c l e . I n p e r f o r m i n g s t o p t e s t s a s u i t a b l e f l y w h e e l c o m b i n a t i o n i s b r a k e d f r o m a r e l e v a n t r.p.m. t o a h a l t . C o n s t a n t speed t e s t i n g s i m u l a t e s t h e d e s c e n t o f a g r a d i e n t and i n t h i s case t h e d r i v i n g motor s u p p l i e s t h e energy i n p u t t o t h e b r a k e .

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T h i s t e s t s t a n d has been i n use f o r many y e a r s i n t e s t i n g numerous drum and d i s k b r a k e s , o f t e n f o r t h e p u r p o s e o f a c q u a i n t i n g s t u d e n t s w i t h l a b o r a t o r y t e s t work. I n c o m b i n a t i o n w i t h t h e analogue computer o f t h e l a b o r a t o r y i t s e r v e d i n t h e e v a l u a t i o n and development o f a n t i - s k i d d e v i c e s . F o r t h e s e t e s t s a pneuma-t i c a l l y a c pneuma-t u a pneuma-t e d f r i c pneuma-t i o n c l u pneuma-t c h was mounpneuma-ted bepneuma-tween pneuma-t h e f l y w h e e l s h a f pneuma-t and pneuma-t h e b r a k e . More r e c e n t l y , a c o n t i n u o u s l y v a r i a b l e t r a n s m i s s i o n and energy s t o r a g e f l y w h e e l was a t t a c h e d t o s t u d y m i c r o computer c o n t r o l o f a r e g e n e r a t i v e b r a k i n g system. These v a r i o u s uses i l l u s t r a t e t h e v e r s a t i l i t y o f t h i s machine d e s i g n e d more t h a n 25 y e a r s ago.

A few y e a r s l a t e r t h e r e a l i s a t i o n o f an i n e r t i a dynamometer o f much l a r g e r c a p a c i t y t h e n t h e one d e s c r i b e d above came o u t ( F i g . 7 ) . Brakes o f heavy r o a d v e h i c l e s , r a i l w a y v e h i c l e s o r a i r p l a n e s can be accommodated. The maximum moment

2

o f i n e r t i a o f t h e f l y w h e e l s i s 5694 kgm . The maximum s t o p t e s t t o r q u e o f r a i l -way t y p e t e s t b r a k e s i s 73.5 kNm and o f a u t o m o b i l e t y p e : 35.3 kNm.

A f t e r a p e r i o d o f t e s t work p r i m a r i l y c o n c e r n i n g f r i c t i o n and wear i n b o t h r a i l w a y and a u t o m o t i v e b r a k e s , t h i s machine was used f o r many y e a r s i n t h e i n -v e s t i g a t i o n o f t y r e l o o s e n i n g , h e a t c r a c k i n g and t h e r m a l d e f o r m a t i o n phenomena i n r a i l w a y w h e e l s . The use o f c o m p o s i t i o n b r a k e shoes was an i m p o r t a n t a s p e c t o f t h i s s t u d y . Most o f t h e s e i n v e s t i g a t i o n s were c a r r i e d o u t i n c o o p e r a t i o n w i t h European r a i l w a y companies. F i g u r e 8 shows t h e f o r m a t i o n o f a h e a t c r a c k .

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F i g . 8 Heat oraoks created during testing on the large brake test stand

P r e s e n t l y t h e equipment i s b e i n g used i n c l a r i f y i n g treadunevenness ( p o l y g o n i -s a t i o n ) o c c u r r i n g -sometime-s on b l o c k b r a k e d r a i l w a y w h e e l -s . T h i -s unevenne-s-s c r e a t e s a n o i s e p r o b l e m , i n s e r v i c e .

Because o f t h e f a c t t h a t t h e e a r l i e r m e n t i o n e d drum t e s t s t a n d was i n a l m o s t c o n s t a n t use f o r t y r e t e s t i n g ' p u r p o s e s and was n o t v e r y w e l l s u i t e d f o r b r a k e t e s t i n g , s i x y e a r s ago i t was d e c i d e d t o b u i l d a new one. The new drum dynamo-m e t e r has been d e s i g n e d t o c a r r y o u t e x p e r i dynamo-m e n t s on a s i n g l e a x l e o f heavy r o a d v e h i c l e s . E x p e r i m e n t s can be c a r r i e d o u t such as s t o p t e s t s , d r a g t e s t s o r o t h e r t e s t s i n w h i c h s i m u l a t i o n o f t h e r o a d s u r f a c e by means o f one o f b o t h o f i t s 1.5 m d i a m e t e r drums a r e a p p r o p r i a t e (max. v e h i c l e speed 140 km/h, maximum a x l e l o a d 120 k N ) . ( F i g . 9 )

The drums may be j o i n e d o r s e p e r a t e d b y means o f a pneumatic f r i c t i o n c l u t c h . Each drum i s p e r m a n e n t l y c o n n e c t e d t o a f l y w h e e l s h a f t t h r o u g h a l a r g e f i x e d r a t i o gearbox. Three f l y w h e e l s o f d i f f e r e n t moments o f i n e r t i a may be c o u p l e d t o t h e s h a f t i n any d e s i r e d c o m b i n a t i o n . One o f t h e f l y w h e e l s h a f t s can be d r i v e n by an e l e c t r i c m o t o r t h r o u g h a f o u r speed gearbox and an e l e c t r o m a g -n e t i c c l u t c h . Each drum s h a f t i s s u p p o r t e d i -n t w o b e a r i -n g s mou-nted o-n l o a d e e l s , c o n t a i n i n g f o u r p i e z o - e l e c t r i c t h r e e component f o r c e m e a s u r i n g e l e m e n t s . The

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e l e m e n t s a r e c o n n e c t e d t o s p e c i a l a m p l i f i e r s i n such a way t h a t t h e v e r t i c a l , l o n g i t u d i n a l and l a t e r a l f o r c e s between v e h i c l e wheel and drum can be d i r e c t l y measured and r e c o r d e d .

F i g . 9 Drum test stand suited for testing the braking performance of

commercial vehicles

A f t e r p r e l i m i n a r y e x p e r i m e n t s , i n v e s t i g a t i o n s o f t h e b r a k e f o r c e d i s t r i b u t i o n o f t r a c t o r s e m i t r a i l e r c o m b i n a t i o n s were c a r r i e d o u t i n c l o s e c o o p e r a t i o n w i t h t h e ' R i j k s d i e n s t voor h e t Wegverkeer'.Now t h i s u n i q u e t e s t machine i s used i n s t u d y i n g t h e b e h a v i o u r o f h y d r a u l i c r e t a r d e r s f o r t r u c k s and b u s s e s , p a r t i c u l a r -l y t h e a n t i - s k i d c h a r a c t e r i s t i c s o f t h e s e d e v i c e s .

The theme Vibrations and comfort comprises t h e s t u d y o f m e c h a n i c a l v i b r a t i o n s w h i c h a r e o f t e n d e t r i m e n t a l t o t h e f a t i g u e l i f e o f v e h i c l e s t r u c t u r e s , t o t h e s a t i s f a c t o r y p e r f o r m a n c e o f components and t o t h e c o m f o r t o f t h e o c c u p a n t s o f t h e v e h i c l e .

V i b r a t i o n s may o c c u r t h r o u g h t h e presence o f e x t e r n a l s o u r c e s , e.g. r o a d and r a i l i r r e g u l a r i t i e s , t y r e o u t o f roundness and i m b a l a n c e , o r due t o o s c i l l a t o r y i n s t a b i l i t y o f t h e v e h i c l e , e.g. bogy ( t r u c k ) h u n t i n g o f r a i l w a y v e h i c l e s , wheel shimmy o f pneumatic t y r e d v e h i c l e s and weave i n s t a b i l i t y o f m o t o r c y c l e m o t i o n . A number o f a r t i c l e s i n t h i s i s s u e o u t l i n e r e s e a r c h i n t h i s a r e a . We r e f e r t o Ryba's a r t i c l e w h i c h t r e a t s t h e more o r l e s s v e r t i c a l r i d e p r o b l e m a r e a o f r o a d

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T _{MECHANICS AND MECHANICAL ENGINEERING} 161

v e h i c l e s ; K e i z e r g i v e s a s u r v e y o f a c t i v i t i e s c o n c e r n i n g r u n n i n g q u a l i t l y ' and s e l f - e x c i t e d o s c i l l a t i o n s o c c u r r i n g w i t h r a i l w a y v e h i c l e s ; P a c e j k a d e a l s w i t h f r o n t w h e e l v i b r a t i o n s and Hofkamp d i s c u s s e s t h e d e v e l o p m e n t and u s e o f c r i t e r i a c o n c e r n i n g c o m f o r t o f o c c u p a n t s . S e v e r a l f a c i l i t i e s f o r t h e h y d r a u l i c a l l y e x c i t a t i o n o f v e h i c l e s and v e h i c l e com-p o n e n t s a r e a v a i l a b l e . A s e t o f f i v e H y d r o com-p u l s a c t u a t o r s ( 1 0 0 0 0 N and 2 5 0 0 0 N, 0.1 m) and two l o n g s t r o k e p e r m a n e n t l y b u i l t i n c y l i n d e r s ( 3 0 0 0 0 N, 0.34 m) f o r r i d e m o t i o n s i m u l a t i o n s . R e f e r e n c e i s made t o R y b a ' s a r t i c l e f o r r e l e v a n t e x a m p l e p r o j e c t d e s c r i p t i o n s .

F i g . 10 Hydi'auliQ actuator facility

T h e s h o c k a b s o r b e r a n d s p r i n g t e s t i n g m a c h i n e f o r m s one o f t h e , o l d e s t a n d f i r s t i n s t a l l e d t e s t b e n c h e s s t i l l p r e s e n t a n d i n u s e i n t h e l a b o r a t o r y . A g r e a t number o f d y n a m i c c h a r a c t e r i s t i c s o f t h e s e c o m p o n e n t s h a v e b e e n a s s e s s e d a n d u s e d i n c o m p a r a t i v e s t u d i e s and f o r t h e p u r p o s e o f v e h i c l e m o d e l l i n g a n d d e s i g n o p t i m i z a t i o n o f t h e c o m p o n e n t s t e s t e d ( c f . F i g . 1 1 ) . A number o f a d v a n c e d and u n i q u e m e a s u r i n g a n d e v a l u a t i o n a p p a r a t u s h a s b e e n d e v e l o p e d i n t h e f i e l d o f v i b r a t i o n s and c o m f o r t . We r e f e r t o t h e a r t i c l e s o f De V r i e s a n d Hofkamp o f t h e d e s c r i p t i o n o f d e v e l o p m e n t s i n r a i l and r o a d c o n t a c t -l e s s p r o f i -l e m e a s u r i n g d e v i c e s a n d t h e r i d e c o m f o r t i n d e x e r .

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F i g . 11 The old shook absorber and spring testing maohine

S e l e c t e d R e f e r e n c e s

E l d i k Thieme, H.C.A. v a n . E x p e r i m e n t a l and T h e o r e t i c a l Research o n M a s s - S p r i n g systems b y t h e V e h i c l e Research L a b o r a t o r y o f t h e T e c h n o l o g i c a l U n i v e r s i t y o f D e l f t , FISITA Congress

1960, Scheveningen, H o l l a n d .

E l d i k Thieme, H.C.A. v a n . Passenger r i d i n g c o m f o r t c r i t e r i a and methods o f

a n a l y s i n g r i d e and v i b r a t i o n d a t a , SAE 295 A, J a n . 1 9 6 1 . E l d i k Thieme, H.C.A. v a n The t i r e as a v e h i c l e component. C h a p t e r 7 o f S.K. and P a c e j k a , H.B. C l a r k ' s Mechanics o f Pneumatic T i r e s , N.B.X. Monograph

122, Washington D.C, 1 9 7 1 .

E l d i k Thieme, H.C.A. v a n . P r a c t i c a l c o m f o r t measurements and c r i t e r i a i n t r a f f i c ( i n D u t c h ) . L e c t u r e h e l d f o r t h e B e l g i a n I n s t i t u t i o n f o r A u t o m o b i l e E n g i n e e r s . B r u s s e l s , Nov. 1 9 7 8 .

D i j k s , A. De a a n d r i j v i n g van de nieuwe r o l p r o e f s t a n d van h e t L a b o r a t o r i u m v o o r V o e r t u i g t e c h n i e k , A a n d r i j f t e c h n i e k , 1 ( 1 9 7 8 ) no. 8.

D i j k s , A. R o l l i n g r e s i s t a n c e measurements w i t h a p i e z o - e l e c t r i c m e a s u r i n g system, SAE t e c h n i c a l paper n r . 8 1 0 1 6 7 . E l d i k Thieme, H.C.A. v a n . Measurements o f t i r e p r o p e r t i e s . I n : Mechanics o f A.J. D i j k s and S. Bobo pneiamatic t i r e s (S.K. C l a r k e d . ) , Washington 1 9 8 1 .