The Black and Decker GH1000 Type 2 string trimmer
A peek inside a Black and Decker string trimmer to determine why the string won't spin provides a good reason to look at its overall design.
By Paul Rako, Technical Editor -- EDN, March 18, 2010
After my disappointment with the performance of string trimmers with 0.040- and 0.065-in. strings, I bought a futuristic-looking Black and Decker model that used professional-size 0.080-in. line. Around the end of the two-year warranty period, the string stopped spinning, even though the motor was still turning. Prying into the interior, I saw that the drive belt had broken and the drive pulley had melted. I replaced the belt with a $7 belt from eReplacementparts.com. Although the company sells the aluminum drive pulley for only $1.42, it does not offer the plastic drive pulley. I spent an hour and still couldn’t figure out how to disassemble the drive pulley. I did make sure I got a spare belt; the new one won’t last long.
The manufacturer used several holes for fixturing during factory assembly. All the screws holding the case halves together are identical in length.
SIP Cinderson of Suzhou, China—near Shanghai—makes the universal brushed motor rated at 120V and 7.2A. It has a nominal power consumption of 874W, or about 1 hp.
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Inadequate structure between the motor and the drive pulley means that the cogged belt will run off the pulleys under heavy loads, such as when you are cutting thick weeds and grass.
The designers added a large flange on the driven pulley to keep the belt from flying off. They also lengthened the drive pulley to keep the belt engaged as it tries to run off the drive pulley.
Although the flange on the drive pulley prevents the belt from flying off, the side pressure creates enough friction to melt the plastic. The molten plastic solidified under the belt, eventually causing it to rip apart.
The designers covered a screw with a decal, making disassembly frustrating. Other than this problem, the design follows good Z-axis assembly practices. You can put every subassembly onto the bottom half of the case, then put on the top half and screw it together all from one direction, the Z axis.
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I have a 2008 model and the trimmer just stopped. I opened it up, per your directions (including finding the hidden screw under the decal) and found the shredded belt. I have a metal pulley already, but I will buy two belts as I have St. Augustine, which is a heavy grass to cut. Any suggestions on the trimmer line. I have substituted .095 which just fits, but the line breaks a lot. What can I do about the line situation?
Matthew Schwartz - 2011-7-8 15:40:17 PDT -
Note that new or refurb units use an aluminum pulley. I wrote this up on my blog. The eReplacement outfit I mentioned in the above tear-down had a picture of the replacement-- get this, you have to buy the whole motor assembly, another "gift" of bad design, but at least the pulley is aluminum. I just bought a whole refurb on Amazon, with free shipping it was cheaper than the replaceable motor. My blog has pics: edn.com/blog/Anablog/40870-The_Black_and_Decker_GH1000_string_trimmer_redeemed.php
Paul Rako - 2011-27-7 14:55:54 PDT -
Well, it was a year before my replacement belt broke, but I will admit to really abusing the thing, I was flailing moss on a concrete patio. It worked great for a while. I put the second belt on, but the plastic pulley has half the cogs melted off. I will be surprised if the replacement lasts through the summer. What pisses me off is that they could have connected the motor and driven pulley with a stiff aluminum structure or made the driven pulley from aluminum or both and this tool would work fine for a decade.
Paul Rako - 2011-3-4 22:17:29 PDT -
My experience exactly. The photos could be mine! B&D Customer Support has been very forthcoming. No explanation of why you can buy the little aluminum pulley but not bad (melted) plastic one.
John J. Kessler - 2010-12-9 16:21:00 PDT -
Thanks for the article. I had a problem with this same model which pointed to problems of QC. The string spool would almost immediately empty. Black and Decker replace it with a second unit which had the same problem. I traced the problem to the trimming blade which was installed backwards, so the string struck the blunt side of the blade instead of sharp edge. Reversing the blade solved the problem. I tried to contact their QC dept but never found a way. A link to QC would be a great link to include in the home pages to give feedback for improvements.
Gerald Lynas - 2010-14-4 12:18:00 PDT
