BH86 / BH860 Boom valve 'speed' adjustment

[Outlawmoon]

Morning All -
This question is in regards to an Asung BH860 or what Branson calls a BH86.

The backhoe works in all respects..... I am looking for a possible way to slow down the boom downward motion. Currently if you push the valve in to pushing the boom down it drops VERY fast. I have to be very careful how far I push the valve lever to control how fast the boom drops. I'm not talking about an inch of movement here, maybe a 1/4 of an inch between a controlled push downward to an all out drop or powered slam....

I will say that I have not yet disassembled the housing to see if there is an adjustment in/on this valve. Looking at the manuals I don't see and adjustment but I do not have a maintenance manual, only a parts and operators manual.

To be clear, this condition has been with this backhoe since I purchased it.

So, if anyone out there knows how to slow the boom downward plunge feel free to drop me a line.

Thanks!!

Outlawmoon

 

[ptsg]

Either a in line flow control valve on the return side of the cylinder when lowering the boom or a Double pilot check valve should solve that issue.

The flow control is adjustable, you would adjust to your needs when lowering while it also gives you full speed when lifting the boom. This requires attention when installing because it's directional. One way it controls the flow, the other way it's fully opened.

The double pilot check valve will lock the cylinder in place and will only move if you pull/push the handle. It won't let the boom "runaway" with it's own weight after you moved the control lever. This will also prevent leakdown of the boom, unless the cylinder is back internally.

 

[ericm979]

In a way it's comforting to hear that the jerky boom problem wasn't just my BH760. I put in two one way flow controls on the boom cylinder as it's jerky in both directions. They are set up to restrict flow out of the cylinder, to prevent cavitation (not that I was sure that'd be a problem).

When I get a chance I'll post the parts I used. The lines are JIC so the valves with adaptors bolt right in. The curl circuit needs one too, it tends to speed up at the end of the curl up travel and flip dirt out of the bucket. Its not as bad as the boom was though.

 

[Outlawmoon]

Thanks guys..... I would have really thought that there would be an adjustment to the flow rate in/on the valve itself.

I'll wait to hear back from Eric979 on those flow control parts.

 

[ericm979]

Here's the parts list from Surpluscenter:

2 9-7960-4 1/4 NPT 5 GPM PRINCE WFC-400 IN-LINE FLOW CONTROL
2 9-2404-6-4 JIC 6M x 1/4 NPTM CONNECTOR
2 9-6505-6-4 JIC 6F TO 1/4 NPTM SWIVEL

and here's a pic

 

[ptsg]

Nice and clean install. :thumbsup:

I think the "problem" is due to the geometry of the curved boom. Curved booms are very sensitive on the max height position do to the way the cylinder has to be placed.

 

[Outlawmoon]

Thanks Ericm979 - I'm getting those flow controls on order today!

 

[ericm979]

I wish I could say the clean install was due to my planning but it's just the lazy way to do it. Also it puts the restrictors where you can reach them from the operator's station for fine tuning. As I put hours on the BH I found I could back them off a little. Hopefully the restrictors are light enough that they don't stress the fittings on the cylinder and crack them. They look fairly strong.

When running the un modified BH it feels like the boom cylinder's valve is oversized. The sweet spot in the travel is very narrow. The other valves don't have that feeling nearly so much. A cylinder geometry problem would make sense.

 

[ptsg]

I suppose you could also use those blank fittings, where your drill a tiny hole to restrict the flow. Those would make the setup more compact but it's harder to adjust and you can't really revert your setting. While the flow controls, as you said, you can adjust any time.

 

[Outlawmoon]

I know what you mean Eric...I've put more than my share of things together and sometimes they just happen to work out really clean on the first try.... When I was younger I just put something together and fiddled with it until it worked the way I wanted it to. Once that happened half the time I would have to remake it so it was clean. As I got older though I spent more time thinking over what I was doing so I only had to build/buy/rewire the item once instead of two or three times.

Of course I still have those occasions when I just slap something together because I need it right now or it's a one-time thing....

I think the cylinder is sized for the down force when digging - that makes it 'jumpy' when there is no load.... It's really the rate of flow that is the issue. Maybe a premade restrictor should have been installed by the factory instead of having to go this route with the adjustable restrictors…. What are your restrictors currently set to? That would give me a starting point.

I'll probably shape a piece of hard nylon to slip under the restrictors and then zip tie it all down to alleviate stress on the cylinder connection...just my first thought on it anyway.

PTSG - I have done that in the past and it was on my mind to possibly do that this time but I thought I'd ask around first. And you know you are exactly right that finding just the right sized hole is a crap shoot. Once you get too big you have to start over again.

Thanks guys for you help and insights!!