arzajac
735 posts
Jan 29, 2012
5:50 AM
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I found Big Rivers on sale at a local store. The price made the choice between a Big River and a better harp not an option. So I tried to figure out a way to improve what I had.
I check the airtightness of a harp by removing the covers and putting my thumb over a draw hole slot and my index finger over the blow slot. I then pucker/cheek some air through the hole and feel how much suction or pressure I can build up. I do this with any type of harp. This one was pretty leaky out of the box as Big Rivers tend to be.
I shoved some BluTak (I found some white "Blue Tak" in case you are wondering) in the trenches in the times of the comb. I made sure that the top was level since too much would make it leak more. I did both the draw and blow sides.
I got the right amount in there and smoothed/polished it with my finger tip. Once I put on the reedplates and tightened the screws, I took them off again and could see where there was too much and where there was not enough by what had squished through. I adjusted the amounts and smoothed it off again.
I checked the airtightness again and there was a significant improvement. This took me about 45 minutes the first time, but I can do it in about 20 minutes now after some practice. I think the improvement makes it worth the time. Definitely an upgrade. It makes it easier to play and less likely to squeal.
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Last Edited by on Jan 29, 2012 5:54 AM
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Kingley
1740 posts
Jan 29, 2012
6:17 AM
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Arzajac - That's a nice solution to airtightness. I remember a few years back guys on Harp L were using Micropore tape to make gaskets for plastic combed harps.
In the UK, I've just found out you can buy 5 Big Rivers for the price of 2 Crossovers. That's a pretty good bargain.
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KeithE
199 posts
Jan 29, 2012
8:13 AM
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Search google images for "harpwrench SP20 Customizing tip" - he used the cord from some hearing protectors there. The image on photo bucket has been deleted otherwise I would just refer to the thread. Would this work on the big rivers too? I wonder how it would compare in terms of time to rework and quality of results?
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jiceblues
63 posts
Jan 29, 2012
10:54 AM
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I can't find it .
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Pistolcat
137 posts
Jan 29, 2012
11:09 AM
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I'm going to try that arzajac. I was just thinking to myself earlier that my new harps (a SP20 B and MBD Bb, new version) were both really nice after basic gapping but that the sp20 leaked a bit too much and squealed a little too readily when OB:d.
One of these days I should put some time on playing instead. Or keep tweaking the harps until they play themselves :)
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Pistolkatt - Pistolkatts youtube
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harpwrench
564 posts
Jan 29, 2012
12:01 PM
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Spiers Harmonicas
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jiceblues
64 posts
Jan 29, 2012
2:10 PM
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THANK YOU !
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isaacullah
1763 posts
Jan 29, 2012
7:18 PM
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Great innovative idea arzajac! I've often wondered if one could use some paint-on liquid latex to coat all the surfaces of the comb that mate with the reedplate. If you could put on a nice, thin, and really even coat, that would make a pretty sweet gasket!
Great idea to use the Blu-Tak, though!
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Jehosaphat
159 posts
Jan 29, 2012
7:59 PM
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Way back when i used to play M/Bs I would buy a tin of 'rubber' paint on sealer that is used to waterproof concrete fishponds.Totally non toxic and no lingering smell.
Nice thin coat let it dry and it made a fantastic flexible gasket.Plus it sealed the wood as well.
Those M/Bs were Airtight.
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HawkeyeKane
681 posts
Jan 30, 2012
7:25 AM
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That IS a great idea! But I'm unfamiliar with the exact product of Blu-Tak. Is this just some kind of adhesive putty? I'm wondering if silicone caulk might also suit this purpose...because evening out the tops of the trenches would be a cinch with the help of a straight-edge trimming tool. I'm gonna try cracking open some of my other cheapy plastic combed harps like Jambones and LoDucas to see if this is an improvement that can be applied to those as well.
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Hawkeye Kane
Last Edited by on Jan 30, 2012 8:53 AM
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STME58
71 posts
Jan 30, 2012
8:35 AM
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I find this whole topic a bit frustrating. Here we are all trying to figgure out how to fix something that should have been made right before it was sold to us. A good molding house would pay attention to their molding parameters and make that comb come out of the mold flat. Instead they are running it as fast as they can because they are paid by the piece and no one seems to care about the customers experience with the product as long as you get the shipments out on time.
That comb probably costs less than 30 cents and it would only add a couple of cents per part more to mold it flat! It might even cost less in the long run as you might get more parts out of the mold before it wore out.
Well enough ranting. Thanks for the good ideas on how to get things working.
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unkyjack
1 post
Jan 30, 2012
3:22 PM
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I'm a beginning harp player and recently bought a Big River in the key of A for the same reason as arzajac -- it was available online at a great price. Mine needed work, too. So far, I've re-gapped it and that's helped somewhat, but it still sounds "leaky."
I'll definitely give these tips a try.
Thanks for sharing the info.
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GMaj7
14 posts
Jan 31, 2012
10:54 AM
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Interesting thread. The gaps are part of the ABS molding process. By keeping the walls of the piece a consistent thickness throughout, it dries and hardens at the same rate and doesn't warp. That's why the stock comb has the grooves in between the slots.
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Greg Jones
16:23 Custom Harmonicas
greg@1623customharmonicas.com
1623customharmonicas.com
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groyster1
1731 posts
Jan 31, 2012
11:26 AM
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I saw where someone said tightening the screws help with the leak issue,but that can make it worse...the big rivers sound okay and have good volume but they are still leaky
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jiceblues
66 posts
Feb 01, 2012
5:44 AM
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You can put a flat sanded BH comb...
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HawkeyeKane
691 posts
Feb 01, 2012
6:32 AM
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I have to say...now that I've played on one of Chris Reynolds' aluminum MS combs...I may just keep getting them until all of them have been swapped out.
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Hawkeye Kane
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STME58
72 posts
Feb 01, 2012
6:18 PM
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Greg,
I see you know something about molding. I was not suggesting that the design was off, but rather that the mold is probably being run too fast without adequate concern for the molding parameters so that pats come out warped. I expect the first shots out of the mold that Hohner evaluated before it went into production were not warped.
Getting some of these low cost molders to do things right is like getting you kids to clean their room, if you do not watch closely, shortcuts will be taken.
Last Edited by on Feb 01, 2012 6:19 PM
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