The Classic Machinery Network

Hello,new member so thanks to the administrator.I have recently acquired a thwaites Alldig,I have seen posts from around 2009 about these but nothing recent,does anyone here have one or know anything about them?..Mine is a later model 1988/9 with Perkins engine,it's to use and ongoing restoration.My current problem is the backactor slews left fine but going right slows down and stops about halfway,I've checked the hoses..Does one ram push and the other pull?..any input appreciated!

Hi Paul and welcome to CMN I am no hydraulic expert but start with the simple things, is there sufficient hydraulic oil in the machine, is the connection to the operating spool valve okay? Make sure there are no airlocks in the system, does the rest of the machine operate okay? I am sure that other people on here like Fred Evans can offer you some good advice.

Jeremy

You seem to have got the ram end disconnected. Do the rams operate in and out with no load? I can't really see but are the ram double acting with 2 feeds each?

essexpete wrote:You seem to have got the ram end disconnected. Do the ram operated in and out with no load? I can't really see but are the ram double acting with 2 feeds each?

Pete it does look like there are two feeds to each ram so double acting rams.

Jeremy

Hi Paul,
I don't know the Thwaites Alldig but here's a thought. If as Jeremy says the rams are double acting and if the engine is under load when trying to slew to the defective side the problem could be the seals in one of the rams.
I have come across a problem a few times on dump trucks when double acting rams operate in pairs where pressure passes the seal in one ram and pressurises the wrong side of the piston in the other ram.
When the pressures each side of the piston equalise in the good ram the check valve in the spool block closes and the system locks up.
If this is the case the ram which stops half way will be the good one.
Fred

Thanks everyone...I disconnected the rams so I could see what was going on..the left ram powers out and back,the right ram does not move at all..I swopped the pipes over at the feed end and the the rams reversed and the one that did not move did!...lol complicated.So they are double acting rams I think..it is a bit low on oil but evrything works apart from this problem..there are 2 connection at top of the rams and one at the bottom end.i have add a couple mor pics...if the problem is as Fred says can the rams be tested?...many thanks again!

northyorkspaul wrote:Thanks everyone...I disconnected the rams so I could see what was going on..the left ram powers out and back,the right ram does not move at all..I swopped the pipes over at the feed end and the the rams reversed and the one that did not move did!...lol complicated.So they are double acting rams I think..it is a bit low on oil but evrything works apart from this problem..there are 2 connection at top of the rams and one at the bottom end.i have add a couple mor pics...if the problem is as Fred says can the rams be tested?...many thanks again!

Can I just make sure I am reading this correctly? Did you swap both ends of one ram around with both end of the other if that makes sense?

Are there just two feed pipes from the spool that then tee off to the opposite end of the next door ram?

thanks...as you will have gathered I am not esp hydraulic savvy...I will give a full explanation of the connections when I look again...there are 2 pipes from the lever end spool...

So you transferred the fault by swapping the pipes over? I would plump for the oil supply feed being the problem and not an internal problem with the ram seals, I was thinking it was a ram problem and the end had come off and was blocking the port, had this happen to me