Rear Main Bearings

[Hedd_Jones]

I've been out in TH today. It needs some hard running to build up some compression which seems to have vanished after a head swap. The axle is noisy. I think the trouble is, the other two cars here have 3 speed boxes. So you struggle hearing anything else!

[David Stepney]

i have been out in FG today too. Went round Bala Lake to put some more miles on the new rear main and to reassure myself that all was well. Well that's my excuse and I'm sticking to it! (See my post in 'What have you done with your Seven Today') I have no experience of three speed gearboxes but I am reminded of a story that I once heard about Lea Francis who bought gearboxes from (I think) Moss Gears. On road test their drivers used to get alongside a tram, If they could hear the gearbox over the tram noises, then the gearbox was removed and sent to Vulcan to fit into their cars! Both TH and the special had synchro boxes whilst FG has a four speed crash box. That's actually quite quiet although second whines like a banshee.

I wonder why you have lost compression after a cylinder head change. What gasket have you used?

[Tony Press]

David,

"As I said in my previous post, I think is has become brinelled. when you rotate it, it feels sometim.es smooth and other times rather rough."

'Brinelling' (named after the Brinell hardness test) is only caused by exceeding the static capacity of a bearing by overloading when stationary- usually through fitting when a hammer blow drives the ball (or unusually the roller) into the track, indenting it.

Not to be confused by 'false brinnelling' which can look similar at first glance. This is often caused when a stationary bearing is subject to vibration which can happen to wheel bearings when carrying autos on train flatcars for long distances.    

The cause of roughness in a roller bearing is sometimes caused by sliding  the rollers across the track under load causing a 'score' on the track when assembling the bearing on the shaft and into the housing.

Bob has mentioned a grey surface on the roller track- caused by wear from dirt in the oil.

Tony.

[Mark McKibbin]

I was much happier with my car after I deleted the muffler otherwise I can recommend ear plugs.

[Bob Culver]

Hi David
 
I trust your scrap bucket is the diy owners sort and the contents never get discarded.  Sometimes a sliver of mild steel can get rolled into a track. If stood for decades could even be some varnish like buildup. Try soaking in paint stripper and see if improves. If worn to unacceptable degree the outer ring likely visibly worn. If convinced it u/s grind away the rivets and dismantle. (The rings are handy as very parallel spacers etc) If barely worn keep the outer ring; it might form a tight match with some other old inner!

[David Stepney]

Hello, Bob,

The scrap bucket is a bit like Windows recycle bin. When it gets full, the contents are examined to see if anything is salvageable before finally going to the metal recyclers.The bearing doesn't look that bad, but feels 'notchy' when rotated.  When it was in the car, it became noisier and noisier to the point that I thought it had actually collapsed. I can't get a feeler gauge of any thickness between the rollers and the out track, so I am at a bit of a loss as to what has come to it. However, the new bearing has now done over 100 miles including a run out to Llanfyllin this evening ( a 60 mile round trip including two sharp climbs into the mountains) and the engine is running as sweetly as one could expect. I am not sure that a 'post mortem' on the old bearing is going to serve any real purpose.

 I have one or two expeditions planned over the next couple of weeks, all of which involve round trips of 50 to 60 miles (if you want to get anywhere it is best not to start off from Bala!) and this evening's trip has boosted my confidence in the little car no end.

I have one or two minor carburation issues, but these are so slight that it may simply me being paranoid. The major one is that the tickover is a bit quick despite the throttle stop being wound right off. I have ordered a carb overhaul kit from Burlems so may amuse myself this weekend with sorting these out.

[David Stepney]

Just to finish this thread off and to reassure anyone who is thinking of replacing their rear main with an uncaged roller bearing, I can now report that FG has done 1500 miles since the bearing was fitted and the little car is running well.

Perhaps I need to be more trusting!

Once again, thanks to everyone who contributed. All of it was most enlightening.

[Ruairidh Dunford]

Great news! Thanks for reporting back.

[Chris KC]

Very interesting David and I'm glad it's going well.

[David Stepney]

To be fair, there is still a bit of rumble at tickover. It is noticeable now that I have got the carb sorted and have a decent 'andante' tickover rather than the 'allegro con brio' one that I did have. My engine is the sort with a roller/ball bearing front bearing combination, so I presume that the rumble is the front roller. Anyway, it goes as soon as the revs are picked up, and, given that it is a 'cooking' engine with, according to the handbook 12 bhp at 2600rpm I am inclined to wait until the engine needs a complete overhaul before doing something about it.

Whilst thinking of funny noises, I had no idea that a worn fan bush could make such a noise until I replaced mine! The "tin tray down stone steps" noise that I thought was part of the nature of the beast has gone completely.