Deeiceb, O. J.
2 The alleged defective condition of the brake seems to be abandoned on this appeal, and the sole question with reference to the machine is whether or not defendant was negligent in not informing plaintiff of the dangers incident to its use. Counsel contend that, by reason of plaintiff’s youth and inexperience, it was defendant’s duty to warn him of the dangers of the brake. The rule upon which they rely has no application to the case, for the reason that the danger was so obvious and patent that his employer was under no obligation to inform him of it. The danger from the use of a machine with revolving iron rollers placed within three-fourths of an inch of each other is so apparent that any boy of fifteen years of age would see it. When one, without objection or promise of repair, works for three years with a machine which is dangerous, and which he knew, or by the exercise of ordinary care ought to have known, was dangerous, he waives the defect, and, if injured, cannot, ordinarily recover. Muldowny v. Railroad Co., 39 Iowa, 615, and cases cited. Again, the duty of the master to instruct and warn the servant only arises as to dangers which the master knows or has reason to believe the servant is ignorant of.' It does not arise as to dangers known to the servant, or that are so open and obvious as that, by the exercise of ordinary care^ he would know of them. Yeager v. Railway Co., 93 Iowa, 1; Newbury v. Manufacturing Co., 100 Iowa, 441. It is clear that plaintiff cannot recover for any negligence in the use of the brake.
*793 II. As to the alleged defective castor in the trow which plaintiff was using at the time of the accident, we are of ■opinion that there was not sufficient evidence, either of defect in the trow; or of the defect, if there was one, being the cause of the injury, to take the case to the jury. There is evidence, it is true, that some trow was out of repair a year before the accident, but no proof that this was the trow which plaintiff was using at the time he was injured. Again, the evidence shows that the trow stopped because of some obstruction on the floor. Plaintiff’s case in these particulars is based almost wholly upon surmise and speculation. In this respect it is quite like Sorenson v. Pulp Co., 56 Wis. 338 (14 N. W. Rep. 446). Moreover, if the trow which ■caused the accident was defective, and had been so for more than a year, plaintiff knew of it; or, if he did not know of it, it was due to his own negligence and want of observation.
4 III. The court refused to allow plaintiff to state whether or not defendant ever told him how to operate the brake, and warned him of the exposed gearings. This ruling was correct. Plaintiff was not injured by the gearing; and the evidence shows that plaintiff, after three years of experience, knew exactly how to operate the machine. Again, if there was error, it was without prejudice, for the reasons stated in the first division of this opinion.
Other rulings on the admission and rejection of evidence are complained of. As a rule, they were correct. Where incorrect they were clearly without prejudice. Prom our point of view, the injury received by plaintiff was clearly an accident, for which no one is responsible. In its facts it is quite like the following: Tinkham v. Sawyer, 153 Mass. 485 (27 N. E. Rep. 6); Buckley v. Manufacturing Co., 113 N. Y. App. 540 (21 N. E. Rep. 717); Young v. Mattress Co., 79 Iowa, 415; McKee v. Railroad Co., 83 Iowa, 616. The ruling of the court directing a verdict for defendant was clearly correct, and the judgment is arrirmeb.