I only want to display 'position' in animation while tend <= 12:
This is the trial:

restart:with(plots):
for tend from 0 to 50
while (tend <= 12) do
pos:=animate(textplot3d,[[-1.8,0,alpha*tend, 'position']], tend=0..50,frames=150);
od;
display(pos);

I receive error messages:
error, (in plots/animate) 0=0..50 is an invalid animation range

Then I try:

restart:with(plots):
while (tend <= 12) do

I have an animated spacecurve with arrow:

restart:with(plots):

p4:=animate(arrow,[<cos(tend),sin(tend),0.9 tend>,<-cos(tend),-sin(tend),0>,color=red],tend=0..50,axes=boxed,frames=150);

I succeed in putting text at basis of arrow:

l3:=animate(textplot3d,[[cos(tend),sin(tend), 0.9 tend, 'basis'],color=black,align={BELOW},font=[TIMES,ROMAN,14]],tend=0..50,frames=150);

I like tot put text at the end of the arrow. This is my 'progress':