"The engine on the Dr.I was an almost exact copy of the Gnome rotary."
Fokker aircraft used Oberursel rotary engines. That company's earlier engines were indeed very closely based on the Gnome Mono, and were fitted to the Eindekker and early D-type biplanes - but the later Oberursel fitted to the Dr.1 Triplane was a copy of the Le Rhone.
Roland Garros was the first pilot to fit hardened-steel deflectors to the prop to enable him to fire through its arc without shooting it full of holes; his aircraft was a Morane-Saulnier Type L monoplane, not a Type N as often reported.
"not to turn off subject here but in WWI did they have a thing in the psitons (i cant remember what it was or where) but didnt it keep the bullets from hitting the propeller? and didnt the planes slow down (just a little not alot) when the guns firing?"
The diagram of the German gun-synchronisation posted by Ack-Ack shows the principles very well. The R.F.C. and R.N.A.S. used a similar system on the single forward-firing Vickers of the Sopwith One-and-a-Half-Strutter (the first British aircraft to be fitted with gun synchronisation). The mechanical linkage was soon replaced by a more reliable hydraulic one and the whole set-up was then developed and produced as the Constantinescu System ('C-C gear') suitable for either single- or twin-Vickers armament; with only slight modifications, it remained the standard equipment on all British aircraft that needed it until WW2, the last types to use it being the Fairey Swordfish and Gloster Gladiator.
And yes, pilots DID sometimes shoot their own propellers off when the gear malfunctioned; it happened at least once to Max Immelmann.
