A  DISCUSSION  BY  MEMBERS  OF  AMERICAN   ÍNSTITUTE  OF

                            ELECTRICAL  ENGINEERS.
 

    Mĸ. Hlood:   I would like to ask  the maximum ac-

ccleration you get thcre in eilher potintls pcr ton or feet

pcr second

    Mr.  Sfrague:   I  cannot  answer  definítely as to

prcsent  practicc,  not  having bccu therc for  nionths.  I

havc socn a numbcr of rccorris showing an average  mile-

scconri rate Up to time of cut-off, autl for the first seven-

tenths  of speed, bcforc workĩug on tlic motor curve,  a

onc and a half nrile-secoutl ratc.

    Mn. Iĩi.ood:   Do you get as high as 100 pounds?

    Mr. Si'Kague: Yes, we do that quitc easily.

    Mn. l'.i.oon:   I know you can, but  I was  wondering

if you did.

    M R.  Sprague :   Ycs.  I  tlrink  so, hut  I   haven't

the rccords wiĩh mc.  I tlriul- vory likoly therc are some

gentlemen  in  the room who havc bccn makíiig  tcsts

on  the road  who  can answer that question  bettcr than

I  ..'iu.   Wc have  gone up to thc slippĩng point of the

whecls,  wlrieh would  be 300 pounris  for cach ton on thc

drivers with normal coiĸiîtion of track.  We rio not  force

ilie maohincs to quite that extent.  lîcing a  two-motor

equipment  with rioublc  trticks,  wc average 61 per  cent.

011 tho drivcrs, and that does not vary with thc loacl morc

thau about 3 per ccnt. eiihcr  way.  I'iftccn pcr cent. a<l-

licsion givos 300 pouncls to the ton if cverything  was 011

ihc drivers.  We can certainly work ĩo ovcr one hunrirctl

anri fifty pounds actual ptill.

    Mĸ. Bi.Ood:   I notiec sonie of thc bcst tcsts  in brak-

ing givc a maximum about 200 pounds.

    Mĸ.  Sí'kague :  Of eourse, in braking you have every

whccl in  operalion, and also all  your  weight.   If  you

should work up to the slipping point, we would have 180

pounds, provided  the track is  in good condition.   We

<lo not work quite so high, for that would leave no margin.

    A  MemũER:   What would happcn if the pilot motor

jamhed  or Imrnt out so that thc controller would not

respond ?

    Mii. Sprague:  That  could  not woll happen on all

thc cars  at once.   There is 110 possiblc cxcuse for small

motors being made so that they are not reliable.  This

particular controller will handle two fifty H. P.  motors,

each of wliich is guarantecd to work up  to 100 H. P. It is

not a very large piece  of apparatus—Ín fact, about  the size

oí an orriinary street car controllcr.

    To operate one of these reqtiires an eighth of a horse

power pilot. This pilot rtins cold.  bccause it only  operates

spasnioilically.  It has only a fraction  of the duty a fan

motor of thc same rated capacity has.

    But let us assume the possiblc conditiou of a  jambed
 

controller.  Nothing disastrous wĩll happen.  If we wish

t" Open  ilic circuît, we  can do  it  instantly  on  thc

reverser without regartl to  ihc maĩn controller, and, hav-

ing oticc opened, it is impossible for that  particular rc-

verscr to conic back until its conirollcr has  bcen rcturncd

lo any determinate position ii  ts sel for.  The revcrser

eircuit passcs  through split paths.   Tlic initial  palh  îs

tiirough a eontact  carricd 011 thc niaiu  controllcr, which.

whcn tho controller has advanced  one step, is  entirely

cul niit. but a supplcmcntal circuit riepeiitlonl  on ihe cur-

rent  iu  ihc  revcrscr  circuit  itsclf  has  meanwhile  been

maric, wliich niaintains that circuit alllĸiugh the original

paih  is  opcn.   If tlris  supplenienlal  contact  for anv

reason opens,  therc is no  method  of again makîng the

main eircuit 011 that car tuitil th:u main controller comes

tt> auy requĩred position,  goncrally  the coast or first con-

lact position.  Of  coursc, if thcre aro tiircc or four cars

in a train, onc ecjuípmcnt can be eulirely cut out, aml the

schedule s]>cccl madc by forcing thc balancc of the motors.

It is  a matter to which wc pay litllo attentĩon in practicc.

This possibility  was  onc of  ihc first  things which t>c-

curred lo us, but it was met by affording two absolutcly

inclcpentlciit  methods  of opcning thc main circnit, one

prefcrably power ririven, and thc olhcr automatic, thc op-

erative rclay  cireuits  of  which are  clcctrically intercon-

ncctc<l so that when once  the main  eirctiit is opcned  ii

caniiol bc agaîn  closed except inĸlcr perfectly safe con-

ditions.  It would,  of eourse, be a serious objection if pro-

vĩsion hari not been macle for tlris vcry possibility.

    A Member:  Would thc fact iliat  a controllcr was

not working bc  known, antl can it bc  rcctifĩcd wlrilc 011

the roari?

    Mĸ. Sprague:  Yes,  but  orclinarily lĩttlc  attention

woukl be paítl to it  until  arriving  at  llic yartls.  Tbe

guartls antl  niotormen vcry soon get usctl  to thc equip-

ment.  If the coutroller docs not movc, thcy know some-

thing is up, and when thcy pass the dcspatcher they re-

port  that 011 a certain car the controllcr is not opcrating.

Thc train does not stop; it  goes on,  When the car is  in

operation, ouc can open and close thc niain circirit brcakers

wĩthout any other  cffect than simply throwing adriitîoual

load  011 the balauce of the equipment, thc cotintcr-electro

motivc íorcc of course protccting llie machincs.

    A Member:  There is one point that Mr. Spraguc

has not touchcd on, I tlrink. and that is the cost of mainte-

nanccaiitl opcration of this intricate automatic mechanism.

and the cost  not only at the  end of one year. but at the

end of tcn years.

    Mr. Sprague:  Wherein lies  the  so-called ĩntricacy