Sentence examples for were difficult to maintain from inspiring English sources

Aircraft made of wood and fabric were difficult to maintain and subject to rapid deterioration when left out in the elements.

On the other hand, high steam pressures were needed to make the engine light enough for use in a road vehicle; suitable engines required expensive construction and were difficult to maintain.

But those valves were difficult to maintain.

While constant voltage was used successfully for electropolymerizing pyrrole, deposition voltages are affected by the number of electrodes addressed and were difficult to maintain using the MX300 in the absence of a reference electrode.

In these cultures, MCs were difficult to maintain for more than two weeks, they did not undergo mitosis and the low number of MCs restricted the opportunities for analysis [7], [18], [51].

Micro-aerophilic conditions for isolation of Campylobacter jejuni were difficult to maintain and results for this organism are omitted.

It's difficult to maintain continuity".

(Was this because the initial energy was difficult to maintain?

But such investment will be difficult to maintain.

It was a difficult project to get started and has been difficult to maintain.

Ground with a steep pitch is subject to erosion, and it can be difficult to maintain.