▁machine . ▁ ▁In ▁ 1 8 8 6 , ▁the ▁company ▁sold ▁its ▁first ▁combine ▁har v ester . ▁It ▁had ▁a ▁ ▁cutting ▁bar ▁and ▁was ▁pulled ▁by ▁an ▁ 1 8 - hor se ▁team . ▁The ▁largest ▁combine ▁Stock ton ▁W heel ▁Co . ▁manufact ured ▁had ▁a ▁ ▁cutting ▁bar . ▁In ▁comparison , ▁large ▁modern ▁comb ines ▁have ▁a ▁ ▁cutting ▁bar . ▁Some ▁of ▁the ▁Hol t ▁comb ines ▁needed ▁as ▁many ▁as ▁ 4 0 ▁horses ▁to ▁operate . ▁ ▁Hol t ▁adapted ▁the ▁combine ▁to ▁work ▁on ▁s lop es . ▁He ▁added ▁two ▁separate ▁wooden ▁frames ▁which ▁enabled ▁the ▁drive ▁whe els ▁to ▁be ▁raised ▁or ▁lower ed ▁independently . ▁This ▁allowed ▁the ▁combine ▁to ▁operate ▁on ▁s lop es ▁as ▁ste ep ▁as ▁ 3 0 ▁degrees ▁while ▁the ▁th res hing ▁machine ▁remained ▁level . ▁In ▁ 1 8 9 0 , ▁Hol t ▁built ▁his ▁first ▁experimental ▁steam ▁tra ction ▁engine , ▁nick named ▁" Old ▁B ets y ". ▁Bu ilt ▁on ▁a ▁ ▁frame , ▁it ▁developed ▁ ▁from ▁a ▁single ▁cyl inder ▁( , ▁). ▁The ▁fire box ▁could ▁burn ▁wood , ▁coal , ▁or ▁oil ▁as ▁fuel . ▁Car ry ing ▁ ▁of ▁water , ▁the ▁tra ction ▁engine ▁we ighed ▁ ▁and ▁rode ▁on ▁huge ▁metal ▁whe els . ▁Hol t ' s ▁tra ctors ▁were ▁popular ▁despite ▁their ▁weight ▁and ▁awk ward ▁size ▁because ▁they ▁could ▁har vest ▁large ▁fields ▁for ▁one - six