Breakdown of Ich hatte die Maschine selbst gebaut, obwohl ich viele Zweifel hatte.
ich
I
haben
to have
viel
much / a lot
bauen
to build
Questions & Answers about Ich hatte die Maschine selbst gebaut, obwohl ich viele Zweifel hatte.
Could I say selber gebaut instead of selbst gebaut?
Yes! Both selbst and selber act as emphatic intensifiers here, meaning "myself" (as in "I did it myself, without help"). selbst is the standard word used in writing and careful speech, while selber is more colloquial and mostly used in everyday spoken German.
Why is selbst placed after die Maschine? Could I say Ich selbst hatte...?
You can put it right after Ich, but it changes the focus slightly. Saying Ich selbst hatte die Maschine gebaut puts heavy emphasis on who did it ("I myself built it, not someone else"). Placing selbst after the direct object (die Maschine), as in this sentence, focuses more on the action of doing it on your own.
Why does the sentence use hatte ... gebaut instead of habe ... gebaut?
This is the Plusquamperfekt (Past Perfect) tense. Just like in English ("had built"), it is used to show that an action was completed further back in the past, usually before another past event. If it were habe ... gebaut (Perfekt tense), it would just mean "I built" or "I have built".
Why is the second hatte at the very end of the sentence?