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pulley size of dynamo


daverclasper
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Hi. My current C40L dynamo on Vitesse appears faulty and seems to be giving out practically nil charge. I will prob convert to alternator, though was hoping this idea might improve the situation for the time being.

Paula kindly donated her old dynamo (which I'm hoping is ok) and brackets to me a while back, though it is a c40.

It looks like I can fit it by shortening the rear "spacer" stub on rear of bracket.

The pulley on this C40 is about 90mm dia, where as my original is 80mm. I think there enough adjustment available to use my fan belt.

Do I need to keep the 90mm pulley, as this maybe gives the correct rpm of dynamo reg output?.   Also I'm hoping to use my RB 340 control box, currently set up for C40L, as the lesser voltage wont harm?.

Also I guess water pump speed will be affected a bit, I'm thinking faster?.

Finally. Will the 90mm pulley have the correct profile for my existing belt?.

Any answers to above and if this is worth trying would be brill, thanks.

Dave         

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I wouldn't do anything irreversible to the spacer stub in case you decide to refurbish your C40L

You're probably fine with either pulley but the larger one will be more prone to not charging at idle. I'm fairly sure they'll be the same belt profile as I think all the small Triumphs used the same V. The control box itself won't be harmed by running a lower rated dynamo but it may "overdrive" the dynamo in an attempt to achieve the output it expects. Probably only with maximum electrical load on, though, and I don't think there's any risk of damage from that.

There won't be any change to the water pump speed as that's determined only by the ratio of water pump pulley to crankshaft pulley.

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I used my dynamo bracket when converting to an alternator as stated the spacer stub had to be shortened but whilst modifying I made it lighter by drilling largish holes in the bracket all over, why! Cause It just seemed to heavy and seemed the right thing to do! I think there are 3 different Lucas alternator pulleys I assume the size Used is determined by the Crankshaft pulley size.

 

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Hi and thanks

Have stripped the C40 down to it's larger parts. Couple of questions please.

The front bush looks like it has been lubed in that area with grease. Is it worth trying to clean through with carb cleaner etc, then using an aerosol grease (warmed up), which is white grease, or, I also have motorbike chain grease in an aerosol. Or clean and run some engine oil in it, like the rear?.

The front cover came off easily with the bush from the shaft. Is it supposed to be an interference fit on the shaft and the bush rotates within a bearing carrier in the cover, if this makes sense?.

Also, is it worthwhile and ok to clean the steel segments on the armature with abrasive paper, that have a bit of surface rust.

Just thought that if this dynamo works ok ish, then might keep it on and worth prepping it a bit, as there has been some bad press reg current alternators.  

Cheers, Dave   

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sand paper is rarely  recommended as it can leave grit deposits 

bushes in general on these are  oilite   need  a soak in oil before use 

white grease is not really for fast revolving parts 

nor is chain lube 

and the shaft should rotate in the bush not the bush in the alloy housing thats very wrong way round 

Pete

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Thanks Pete, It's actually a steel bearing at the front, secured by a large circlip, which is shown on parts diagrams as well. Hence the apparent grease.

It's feels smooth running, so I'm thinking I'll leave it alone, just in case I cause one of my disasters, by meddling (don't know how easy it is to get out/refit, if an interference fit on the outer edge ect).

Cheers, Dave

Edited by daverclasper
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Thanks Pete.  It's a normal bearing in the front cover and the inner race turns smoothly and feels like it still has grease in it.  It's not a tight fit on the shaft, more like snug.

I gather this should be a tight fit, according to an article online. This guy rebuild a C39 which is very similar and his bearing to shaft was not tight. He used a form of Loctite. He seemed to now what he was talking about?.

Should I do the same, do you think.

Dave  

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dave you said earlier it was a

On 10/10/2020 at 19:22, daverclasper said:

The front bush looks like it has been lubed

 bush ,, so is this a normal ball race as i would expect or just a tube type bush 

 

a ball race will be tight on both shaft and case an needs a drag or press or vice and whacker to remove it 

you dont want anything rotating in the alloy front cover it will simply wear out super fast 

Pete

 

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definitely a ball race and I got one for a couple of quid from an ebay bearing stockist. Pretty easy to replace although the modern bearings come with integral seals rather than the separate of the original. The old one was pitted so turns much smoother now but not tested in anger yet.... 

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Thanks. Yes It's a ball race. in the semi gloom, (one light bulb went, at the time) I assumed it was a bush (same as rear) though realized after my post. Apologies, if not clear.

So, Loctite inner bearing race to shaft?, in case it's prone to spinning.

Edited by daverclasper
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I think if its going to spin it would be the outer race in the alloy housing not on the shaft which is quite tight. However unless the bearing is starting to seize I cant see any reason why it should do this....

I remember now the biggest problem I found was that the threaded section on the end of the shaft was very soft and although I used the nut on it to spread the load when hammering the shaft through the bearing it still got damaged and had to be reformed. 

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49 minutes ago, johny said:

I found was that the threaded section on the end of the shaft was very soft

yes thats a common problem whilst the shaft may ?be toughend threads are kept soft , and agree its easy to bludgeon them to useless

if you wish to use a bearing fit loctite then that would be out race of the  bearing fit in the front case , the steel shaft will be fine its the soft case you dont want any spinning going

the bearing should be a light tap to fit tolerance in the front case 

dont get any' bearing fit ' inside the race ...makes it very lumpy !!!

Pete

 

on 

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48 minutes ago, Pete Lewis said:

the steel shaft will be fine its the soft case you dont want any spinning going

Thanks, so would a slight smear of grease on the shaft help, if it may be prone to spinning on inner race (It's not a tight fit). I presume grease would also prompt it to spin?.

Also what's "bearing fit" please Pete.

Sorry if this is going on a bit.

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I'm a bit confused.  I'm haven't tried to disturb the bearing, though assuming it may be still tight in the housing?.

It seems the only obvious thing out of spec, is the inner part of bearing, which is snug, rather than tight on the shaft, so was wondering if to Loctite it, or if it doesn't matter that shaft may spin on inner part, then just to give it a bit of grease to help it along and a bit less wear?.

Cheers, Dave      

Edited by daverclasper
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the shaft is hardened and ground to size it wont wear by spinning in the race , if you want to grease it  feel free

if the outer race is a nice fit in the housing leave it alone just your earlier post suggested the bearing or bush was likely turning in the alloy case 

as it was tight on the shaft             

well thats the drift i got 

Pete

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If the dynamo is not outputting current in my experience it is usually the control box at fault as this energises the coils as needed. easy check once back together do not connect the small wire on the dynamo then to put a voltmeter across the battery terminals (old fashioned needle probably better as it reacts faster) with the engine running put 12 volts to the dynamo small terminal and the voltage should rise disconnect and back to 12v, if it does the dynamo is working. The control box switches this on and off and is generally the cause of dynamo charging issues.

 

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8 minutes ago, DanMi said:

If the dynamo is not outputting current in my experience it is usually the control box at fault

It can be, but in my experience it never was. Failed brushes also cause no output, as do broken wires. That's why I have a few old dynamos in a drawer but no control boxes (although my current fleet are all on alternators so the spares aren't much use to me)

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My original C40L and second one (a private sale on E Bay, as a recon, it looked like one too, new covering around the fields, new terminals, wiring. brushes, etc and clean), though didn't fit it until way after I bought it, Doh.

 rpm Both failed the "bridging the two dynamo terminals" test by producing low voltage at 700 rpm and higher (I also made sure it was earthing with jump lead from dynamo to battery).  The more involved tests on both with them dismantled were ok. So a bit surprised, though apparently the only proper test is with a growler.

My ignition light would go out above idle, though I assumed this was because it was producing some voltage  

Edited by daverclasper
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