Hi, New Owner Thwaites Nimbus 40M box

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robinwelch1000
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Hi, New Owner Thwaites Nimbus 40M box

Post #1 by robinwelch1000 » Tue Nov 10, 2020 7:09 pm

Hi All.

I'm new here and to Dumpers, I'm looking for some help with Nimbus 40M gearbox, gears very crunchy and I don't think clutch is fully working, any advice for a novice, pics available
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Jeremy Rowland
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Re: Hi, New Owner Thwaites Nimbus 40M box

Post #2 by Jeremy Rowland » Tue Nov 10, 2020 9:09 pm

Hi and welcome to the site :wave: I am guessing that the clutch is either mechanically activated by a rod? If so there should be some adjustment on it? If not then it must be hydraulically activated? If so there may be no adjustment possible which may mean replacing the clutch unless you have a master or slave cylinder fault, is the pedal spongy when you depress the clutch? There are plenty of dumper owners on here who can offer better advice than me.

Jeremy


essexpete
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Re: Hi, New Owner Thwaites Nimbus 40M box

Post #3 by essexpete » Tue Nov 10, 2020 9:19 pm

When you say crunchy do you mean from standing start or changing on the move?

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FOWLER MAN
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Re: Hi, New Owner Thwaites Nimbus 40M box

Post #4 by FOWLER MAN » Thu Nov 12, 2020 5:52 pm

Jeremy Rowland wrote:Hi and welcome to the site :wave: I am guessing that the clutch is either mechanically activated by a rod? If so there should be some adjustment on it? If not then it must be hydraulically activated? If so there may be no adjustment possible which may mean replacing the clutch unless you have a master or slave cylinder fault, is the pedal spongy when you depress the clutch? There are plenty of dumper owners on here who can offer better advice than me.

Jeremy


Hi Jeremy,
The dumper Robin has looks to me like an old Thwaites Nimbus. I haven't worked on one since the 1960s, but from memory, it will have the Thwaites rod operated "brake drum clutch."
The first thing to say is that the Newage box is a crash box with no synchromessh so a clean change on the move is difficult to acheive. Also it's worth checking the oil in the gearbox because water ingress was always a problem!!

If however it's difficult to get the gear to engage when stationary it does point to the clutch. First check out the linkage and clutch release bearing. If all is well adjust the linkage to give approx one and a half to two inches of free movement at the pedal.
To adjust the clutch tighten the square adjuster on the brake/ clutch drum back-plate all the way until tight. Get help to push the pedal to the fully disengaged position and hold it down. Then slack back the adjuster a few flats till the drum is just free to move.
Thwaites drum clutch below.
I hope this helps.

Fred
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Whitlock 505
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Re: Hi, New Owner Thwaites Nimbus 40M box

Post #5 by Whitlock 505 » Sun Nov 15, 2020 10:36 pm

Hi

I rebuilt a newage 40m gearbox and they are prone to the front bearing wearing out on the layshaft collapsing and causing difficulty in engaging gears, they have been replaced with a bronze bush which is available from L&SPLANT Engineers
Hope this might help if Fred's diagnosis does not prove to be the cause (bearing number 16 in the attached photo)


Ian
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