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Sprung hornblocks...is this method right?

Sprung hornblock




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#1 JeffP

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Posted 14 February 2013 - 12:46

Can any of our resident experts tell me if I've got this right, please?

If I were to use 6 hornblocks on a 6-coupled loco, I use the screws supplied with them to set the ride height, so that NORMALLY the loco rides with the hornblocks resting on the screws.
Then, if it encounters a bump, the wheels can move down to keep in contact with the track.
I shouldn't expect the wheels to move UP at all.

Is that right?

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#2 Horsetan

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Posted 14 February 2013 - 13:06

I have difficulty with that. Axles should be permitted to move a little up and down. If your engine encounters a hump, how is the leading axle going to be able to move up to cope with the rise if the screws are blocking it?


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#3 Gordon A

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Posted 14 February 2013 - 13:25

Unfortunately some springing systems are designed to push the wheels into hollows. As Horsetan says the ideal system should allow the axles to rise as well as fall. You have not mentioned which system you are using. Can you buy spare strings that are of a higher rate? You could try setting the ride height on all six axles, then back off a few turns on the middle adjusters to allow the middle axle to rise say 0.25 to 0.5mm. Gordon A Bristol

#4 meil

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Posted 14 February 2013 - 13:39

Can any of our resident experts tell me if I've got this right, please?

If I were to use 6 hornblocks on a 6-coupled loco, I use the screws supplied with them to set the ride height, so that NORMALLY the loco rides with the hornblocks resting on the screws.
Then, if it encounters a bump, the wheels can move down to keep in contact with the track.
I shouldn't expect the wheels to move UP at all.

Is that right?

I assume you mean 12 Hornblocks?

 

You usualy have the four outer hornblocks resting on their stops on level track. The two centre hornblocks arethen  usualy adjusted so they have about 0.5mm upward movement on level track.



#5 JeffP

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Posted 14 February 2013 - 14:05

I assume you mean 12 Hornblocks?
 
You usualy have the four outer hornblocks resting on their stops on level track. The two centre hornblocks arethen  usualy adjusted so they have about 0.5mm upward movement on level track.


Errm, no, it's a 4-6-2, so six coupled = 6 hornblocks?

I was looking at using Martin Finney's etched LNER hornblocks.

Horsetan: I assumed that wheel would move slightly UP taking the loco with it, and the others would move down to maintain track contact?

So how DO sprung hornblocks work, then? is the loco's weight carried on the tiny coil springs? How do they cope with differing loco weights, since the same hornblocks might be used on, say, a DJH cast pewter model and an all-brass etched kit?

What do the screws do, if not set ride height?

The only time I have used hornblocks before, I built the loco with compensation: it worked, but I wasn't keen........

#6 wenlock

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Posted 14 February 2013 - 14:28

6 Wheels, 6 hornblocks as far as I'm concerned! I've only experience of using Slaters sprung hornblocks in 7mm scale, however I've tried others during my 4mm days. I initially adjust the screw stops so that all six wheels are resting on their stops on a piece of glass. Check there is no rocking of the chassis and that it is horizontal both laterally and longitudinally. Once I'm happy that all is in order I back of the CENTRAL axle hornblock screws to allow a millimetre of upward vertical movement on this axle.

I hope this helps, it works fine for me!

Dave
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#7 Miss Prism

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Posted 14 February 2013 - 14:40

Jeff - the term 'sprung hornblocks' covers a multitude of sins. The system you describe in your OP is what is commonly called 'spring-assisted', which is where a (comparatively weak) spring depresses a wheel into a hollow, but where the chassis is otherwise sitting on fully-compressed springs, i.e. the chassis is still, in effect, for the most part, rigid, and where the screw does set the ride height. Other coil spring hornblocks, e.g. the Brassmasters one in 4mm, is where the strength of the spring is such where the wheels do sit somewhere in the compression range of the spring without compressing it fully, i.e. when a wheel encounters a track hump, upward movement is accommodated without a hard bump being fully transmitted to the chassis.

The problem with small coil springs is that their springrate cannot easily cope with widely differing loco weights, as you correctly surmise.

The problem with 'fully sprung' (if I may use that term) springs is that setting the ride height and getting the spring strength correct are interrelated, and therefore somewhat problematic. CSB technology provides a good route to addressing this holistic issue.

Whilst 7mm CSB applications are still relatively rare (Adrian Cherry is a convert), I think one of the problems in 7mm is that, unlike 4mm, where we have a reasonable consensus on what locos of a certain size should weigh, there appears to be little discussion or consensus on that matter in the 7mm world. Most 7mm builders, on being asked what their locos are finally weighed at, often respond with a puzzled "I have no idea" or "Sufficient!" or "I don't understand the relevance of the question."
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#8 JeffP

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Posted 14 February 2013 - 17:44

Hmmmmmmm, yes, CSB.......

That attracts me, but it seems to need so much forethought.

Looks like I should go away and forethink.

#9 Jeff Smith

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Posted 15 February 2013 - 00:05

The Gibson 4mm hornblocks are 'spring assisted', if that is the right term.  Some time ago I built an industrial (small wheels) 0-6-0 using Gibson hornblocks.  The instructions (which I can scan if requested) say to fully retract the middle screws, level the loco on the outer screws at the midway travel mark.  This leaves some upward movement for the middle axle - it doesn't specify how much but assuming you have attached the hornblocks exactly level then this would be half the travel.  In my case around a mm.  Too much relative travel and the coupling rods are in danger of locking up - it goes without saying that hinged coupling rods are essential.  The jury is still out about whether I would use these again.  The drive is to the rear axle but conceivably you could drive the centre axle.



#10 Jeff Smith

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Posted 13 September 2017 - 16:26

Just wanted to resurrect this thread as I am considering using the Gibson sprung hornblocks once again and wondered if there was any fresh insight on these. The subject will be a 4-6-0 with drive to either the rear or centre drivers (Wrightlines Baldwin in 0-16.5). The reasoning is twofold, first for reliable pick-up and secondly to allow the Gibson wheelsets to be pre-assembled and drop-in.

Anyone had any recent experience?

#11 ian@stenochs

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Posted 13 September 2017 - 20:38

If the body weight is supported on stops, such that the only movement the axleboxes can have is down, then the loco is on a RIGID chassis. When any wheel hits a raised part of the track, a slight misalignment of a joint etc the loco will lurch.
However if the loco rides on the springs such that each axlebox can rise or fall from the datum then it will glide over any irregularity and the body will hardly deviate from level. That is a SPRUNG chassis.
Making a sprung chassis does require more work to get the ride height correct and can only be done once the loco is completed and the body its final weight but the effort is rewarded by superior running. Probably the simplest method is csb of which I have no experience as I work in 7mm scale. My experience is with individual coil springs on the top of each axlebox which do need shimming to get ride height.
Ian.

#12 Torper

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Posted 13 September 2017 - 22:39

Working in P4, I have never managed to get the Gibson spring assisted system (which is described in the OP) to work satsfactorily.  I've never tried the Brassmaster springing system.  My best results have been with good old fashioned beam compensation though I have also had some success with CSBs (even when I don't use them on the loco I now always use them on the tender).

 

DT


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#13 Daddyman

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Posted 14 September 2017 - 06:08

Working in P4, I have never managed to get the Gibson spring assisted system (which is described in the OP) to work satsfactorily.  I've never tried the Brassmaster springing system.  My best results have been with good old fashioned beam compensation though I have also had some success with CSBs (even when I don't use them on the loco I now always use them on the tender).

 

DT

I'm the same with Gibsons, despite Horsetan's advice. And didn't I read somewhere that Gibsons when fitted in standard chassis cut-outs will only allow downward movement? Am I right in thinking that the frame cut-outs would have to be extended upwards in order to get upward movement? My experience was that if I wanted to allow upward movement the screw would have to be screwed out so far that there was nothing to hold the spring. That, and excessive slop. 



#14 Torper

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Posted 14 September 2017 - 08:19

The Gibson spring assisted system only ever allows downward movement. The only advantage it has over a rigid chassis is that if one wheel goes up for some reason, the others should stay on the track.  Even if it works like that, of course, it doesn't stop the loco lurching as it passes over any slight bump in the track.

 

DT



#15 Horsetan

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Posted 14 September 2017 - 08:28

The Gibson spring assisted system only ever allows downward movement....


Only if built as designed. There's nothing stopping you converting it to individually sprung (Pendlenton-type) or CSB.
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#16 Torper

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Posted 14 September 2017 - 08:40

Only if built as designed. There's nothing stopping you converting it to individually sprung (Pendlenton-type) or CSB.

I was under the impression that the OP was talking about it being built as designed.  If you're going to "convert it", especially to CSBs, you'd be better off starting with a CSB system from scratch rather than "converting" the Gibsons.

 

DT



#17 Jeff Smith

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Posted 14 September 2017 - 08:54

So what type of hornblock is preferred for drop-in capability?  I'm thinking maybe a conversion of the Gibson one in discussion with stronger springs (it's a heavy white-metal body)?



#18 Izzy

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Posted 14 September 2017 - 10:47

Just wanted to resurrect this thread as I am considering using the Gibson sprung hornblocks once again and wondered if there was any fresh insight on these. The subject will be a 4-6-0 with drive to either the rear or centre drivers (Wrightlines Baldwin in 0-16.5). The reasoning is twofold, first for reliable pick-up and secondly to allow the Gibson wheelsets to be pre-assembled and drop-in.

Anyone had any recent experience?

 

If you are thinking of using Gibson hornblocks to allow split axle current collection - that is the basic reasoning isn't it? - then I would say that in my experience of using it in 2/4/7mm scales, split-axle current collection through enclosed brass bearings isn't any more reliable than wheel rubbing collection, and often less so. In 2mmFS most add what have become known as 'Simpson' springs, fine sprung wire rubbing directly on the axles, to ensure reliable current collection.

 

I have used Gibson hornblocks on and off since they first arrived on the scene - in fact I alerted users that the first/original hornblock mouldings weren't symmetrical  and allowances had to be made for this - and as others have mentioned these hornblocks are of the spring-assisted type as are most others for the reasons given of the difficulty in obtaining springs with usable spring ratings that can both support the weight of a loco but give under it at the same time. CSB's are a method that has arrived to try and overcome these issues.

 

If you fancy split-axle collection then using the Gibson hornblocks sans springs and with stiff sprung wire as joint current collection/csb's - bearing straight onto the axles otherwise there is no advantage -  would be my suggestion, but as ever it's a question of each to their own.

 

Izzy



#19 Torper

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Posted 14 September 2017 - 13:30

So what type of hornblock is preferred for drop-in capability?  I'm thinking maybe a conversion of the Gibson one in discussion with stronger springs (it's a heavy white-metal body)?

 

I've always found MJT hornblocks satisfactory - i've used them both for compansated chassis and, with the addtion of Romford handrail knobs, for CSBs.  While I haven't used them for a long time, I've no reason to think that the basic Gibson hornblocks (as sold without the springs) are fine.  High Level do a range of hornblocks specially designed for CSBs, but a they are a little fiddly though they do work.  If you're still wanting to use individual springs, then the Brassmasters ones may be best for you as they act a bit like the Gibson ones but allow both up and down movement.

 

DT



#20 Jeff Smith

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Posted 17 September 2017 - 09:31

My choice of hornblock may come down to wheel choice. If Gibson, notoriously hard to get square on the axles, I would prefer drop in blocks. But if Romford/Markits, standard closed one's would do.

Edited by Jeff Smith, 17 September 2017 - 19:34 .








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