Bartacks made with straight stitch?

[Bill]

Advice frequently given to me is use the handwheel if the machines motor isn't up to the task. I dare say the gears etc are plenty beefy enough to cope with whatever fabric you're using as is the needle (depending on its size and type)
But yep, bar tacks aren't usually that long so try just using the handwheel for those bits.

[BrendaP]

I am confused. Do you mean back in "old times" they were handstitched?

Depends what you mean by 'old times".  200 years ago everything was hand stitched.

All of my 'how to' sewing books, except the one by Threads including a 2009 publication by Alison Smith, refer to bar tacks as several layers of thread covered with hand-made button hole stitch.  Bar tacking as a machine operation is relatively recent, certainly within the home sewing sector.