| jessie.dazzle wrote:|
Two things I see that may or may not turn out to be an issue:
1) The relatively narrow stance of the front wheels; depending on how heavily you load the top of the frame, stability could be a bit on the limit when moving things around, especially on carpet. You will also very likely end up slightly shimming one side in order to get the mast completely vertical (you will be dealing with French floors...); jacking one side to shim it can be a bit tedious with a narrow stance.
This is also my worry and has been from the start. In the end, I decided to accept a compromise, that is keep the front span of the legs fairly narrow so that I would not have to see the castor wheels from the listening position. Obviously my hope is that the weight of the UB115 horn with a centre of mass away from the mast will act as a strong cantilever to the weight from above. Having lifted the horn today (it got delivered from a van by Russ and was transferred to a truck taking it to France in the same breath!), I realise it is not as heavy as I would have hoped, a mere 70kg or so. Still whilst moving the frame about with the horn placed on it, it felt fairly stable and easy to manoeuver. Russ in fact commented how misleading it was handling the combination as a light push would give it a fair amount of momentum.
The weight of the midrange horns as they are presently will not present a problem as the horns built for me by Hajo Steffen from Huertgenwald in Germany are made of fibreglass and are relatively light. I have been waiting for these horns to be delivered for nearly four months now and live in hope that this will happen before Christmas.
Eventually, I may well have heavier horns for the 'fundamental channel', maybe even a 180-200Hz made out of mdf or laminated birch ply, and then the narrow stance of the front cradle may well prove a problem.
I do have carpet in my front room in the UK and I know too well how much of a bane they are for most castor wheels available on the market but in my place in France I have had, thankfully, wooden flooring fitted earlier this year. How level the flooring is, in this centuries old, traditional alsatian house, I have not checked but will find out when I am there in a few days' time to accept delivery of the LVframe and UB115. The fitter, a maitre artisan of the 'Compagnons du Tour de France, a guild that dates back to the medieval ages (http://en.wikipedia.org/wiki/Compagnons_du_Tour_de_France), who happens to be a pilot in his spare time, seems to have done a really good job:
Parquet installation and detail of my lounge/listening room in Ribeauville, France
Parquet installation again
Parquet installation - labour of love following the contour of the irregular stone walls around the rooms, with no convenient skirting board
I am sort of hoping that by some miracle that this house that does have not a single pair of parallel walls to its name anywhere over its four floors has perfectly level floors! I guess that if I am not that fortunate, I will just have to deal with uneven flooring by following your suggestion, that is shimming rather than using the stem to level the LVFrame if needs be.
| jessie.dazzle wrote:|
2) The casters you selected are of the stem-mount variety; keep them tight! If they start backing out, the stem bends when pushing around the heavily loaded structure, again especially on carpeted floors, especially if there's a lot of padding. The bent stem then jams the steering function of the casters. Nevertheless, really good stem-mount casters will withstand this sort of abuse, in which case the caster mounting plate and mounting bore must also be up to the job. I wouldn't expect any catastrophic failures here but the plate might work loose over time. Above all, don't use the stems to level the frame; screw all stems in until the upper bearing races firmly contact the frame mounting surfaces; use shims between the wheels and the floor to make it all stand up straight.
Again, I chose the castor wheels after pretty much driving poor Russ round the bend, discarding hundreds of contenders because they were too industrial looking whilst he discarded just as many because they were not of the stem variety ( I wanted to have adjustable castor wheels precisely in case I encountered uneven floors but I feel given what you have said above that this would be rather ill-advised). I also needed castor wheels which could accomodate a total load of 400kg (my rough figures were based on 100kg for UB115 including back chamber, 100 kg for LVframe, 20-30 kg for lower MF, 10kg for tweeter, 30-50 kg for upper MF, and potentially 30-50kg for Injection channel plus 50kg safety margin) divided over three castor wheels even though the LVFrame would have four wheels.
I do not know how good these castors by Tente are supposed to be, but given that they seem to be a fairly huge German manufacturer that specialises in just castors and wheels, I suspect they ought to be very good indeed. When I came across Tente, http://www.tente.com, that makes a large range of castor for very different applications and end-users, after going through their extensive catalogue, I was immediately sold on the 'Levina' range of castors by the German castor specialist, the Levina being a range intended for institutional customers, not because it has 'LV' in its name but because it avoided the 'industrial look' of most heavy load bearing castors, with a load capacity of 100kg (200kg static) per castor (Levina 5370PJP125P30-11)
As things currently stand, I have the silver/grey versions which Russ ordered as he believed that they were only available in that colour (I had the castors' 'chassis' painted black. However, thanks to your query, I now realise that as on the picture I kept referring to that they are available in graphite/black which are the ones I will be ordering to replace the current ones (as I also use these castors in a smaller version the two matching coffee tables I had made out of Lignum Vitae, I need to order 16 of these!).
I think that these castors will work a treat on my wooden flooring, given their intended market, and the amount of thought that went in their design (they won a design award in 2009), but will wait until I know more to report on their performance. Given that the mounting for these is fairly standard, I may be able to change to other better performing castors if need be eventually. If in the end, I don't feel completely happy with their looks, I may also still replace them with some appropriately designed feet, that will go on the frames once their fixed location has been established, as Romy suggested somewhere I think.
Thanks for the advice on how to use and mount these castors. I certainly did not realise that levelling them using the stem was a poor idea although on reflection, I can see that you are probably right. I remember some furniture castors I had fitted to some air suspended Arcici racks years ago and how they would not last a few days of use even though they were recommended and supplied by the rack manufacturer. In the end, I asked the British distributor to find some other heavy duty castors, which he duly did and which I still use to this day on all four Arcici racks I use in my main system. So I understand the need to find the right castors and hope these Levina ones will be up to the job (especially once they are all replaced with the so much sexier graphite/black ones!).