Brrr!
Posted by sara (betsie's mom) on 06 Feb 2007 at 05:46 pm | Tagged as: General
Hard to believe the groundhog was serious about spring coming soon
when it’s 10 degrees (F) in Virginia….
I didn’t put Betsie into indoor storage because we haven’t really had
any rain or snow around here. I do check now and then and make sure
she’s still receiving power… but she’s been in Pause mode since late
November.
Do you know what caused your blades to break? Do you have rocks or other hard items in your hard? It’s rare to see this for a Robomower, but I’ve seen several Lawnbott blades break. I’m curious as to why.
Love your site!
http://forums.robomower.biz (Open forum for all robotic automatic lawnmowers)
http://www.lawnbotts.com (A nice place to purchase robotic lawnmowers)
I’ll ditto the above question… here in TN our grass was growing in January this year, so during a warm time I sent Oscar Mow Mow out for a touch up. Unfortunately Oscar didn’t make it too far before his blade broke. I put him back on pause and ordered a new blade. When it came I installed it but I didn’t send Oscar back out into the yard again until last week. Would you believe he broke a blade again yesterday (yes.. the blade only had a week of use when it broke- sigh)!
Both of my breaks were identical and virtually the same as the picture of Betsie’s breaks. I identified the first break as being caused by a decent size piece of gravel that was thrown into the yard from our driveway (my fault, I missed it when I checked the yard), but I haven’t for certain yet found anything that caused yesterday’s break (in fact I haven’t even found the blade fragment yet!) Both of my blades seemed to snap off at the small hole about an inch from the end of the blade (I assume those are drilled to balance the blade?). I’m not an engineer, but I wonder if the manufacturer could change the hole location (lower on the blade where the blade speed/vibration stress is less) and/or changing the balancing method (edge removal instead of a hole) to help these not break so readily. The end of the blade is under a lot of stress (it’s traveling nearly a mile every second while cutting: 1/2 ft. * pi * 3000RPM comes in around 4700 ft/sec) so any hole in that area of thin of metal is going to be a candidate for developing a stress fracture and eventually breaking along that fracture.
I’ve only owned Oscar since September and have already went through 2 blades. Although I already disclaimed that I’m not an engineer, I am inclined to believe that some improvement could be done with this aspect of the Lawnbotts.
There’s a lot of variables that go into the design blade… weight, speed, vibration, battery life, material properties… Typically, an engineer thinks that a design can always be improved upon. Whether they can justify the trade-off to cost, etc is another question… especially if they’re making money off broken blades. 🙂
I know that before Betsie’s broke they had been bent and re-straightened multiple times over the summer. I figured that this weakened the metal enough for it to eventually snap off. I’m thinking the culprit was some tree roots along the side of the house.
First, a correction to my earlier message… that’s 4700 ft/min, not ft/sec… I don’t know what I was thinking. Still, it’s coming close to 60 mi/hr.
You are correct- I did greatly oversimplify the engineering involved in order to make my point about perceived design flaws. Personally, I’m a software developer… and we can’t do faster, better, and cheaper all at the same time either. There are always compromises somewhere.
Still, I wish the blade could be improved, but as you said there isn’t really an incentive to do so if the company will lose money in the process. I notice that some dealers have caught on as well… charging $40 for a blade!
I still haven’t found the last blade fragment or what caused it to break. In fact, the only anomoly I’ve found so far is a mole hill that got shaved off (pesky moles… no matter how hard I try I can’t get rid of them).
I think KA is a better company than to rip us off on badly designed blades… but I did have the same line of thought as you (why redesign it when we’re making a profit on replacements!)
I’ll suggest you drop a note to the KA people using their web contact form. They definitely read the emails, and you might get a reply.
http://www.lawnbott.com/contactus.aspx
I wrote KA a couple weeks ago regarding the blades. Their web form cuts off the text after 200 or so characters, so they had to respond via email to get the rest of my message. Indeed, they did seem interested, but I have not heard back since resending by email the full content of my message. Time will tell.
In the meantime Oscar seems to be exhibiting a software glitch. He has stopped mowing zone 3 automatically… although he is set to leave his wire for zone 3 after 9 minutes of following his wire, he just follows all the way around to his charger (14 minutes) where he waits a couple hours and then proceeds to do the next scheduled zone. I have to manually release him in zone 3. Twice he has also done this with zone 2 (which is set at 2 minutes 20 seconds). The glitch seems random with zone 2, but always happens with zone 3. I am writing KA about this today. Has anyone else seen this with their Lawnbotts?
I just wrote KA again asking if there was any update on my earlier blade inquiry. Here is the official response:
“We did get in touch with Zucchetti and they had originally put the holes it the blades to attach a plastic piece that would help prevent deep cuts from the blade if it were to ever cut someone’s. But with the plastic pieces the run time on the unit was dramatically reduced down to less than an hour. They have started producing the blades without the holes and they should be available soon. “