Heljan OO Park Royal Railbus sound/decoder fitting

[Ray H]

Apologies if I've posted this in the wrong place perhaps a Mod can move it for me.

 

I've finally found some time to look at fitting sound into an OO gauge Heljan Park Royal Railbus that I bought several months ago. I have a Zimo MX645 decoder, small round speaker and a stay alive capacitor. The decoder has a harness instead of the 21 pin plug that should fit into the socket on the railbus.

 

It took a while to get the body off but having done so and gained access to the decoder socket area, there seems to be a mass of red & white wires. I can see a grey and a black wire but no orange wire so I'm at a loss to know which wires to connect to where on the decoder.

 

Likewise, it appears that the only place for the speaker could be resting on the floor in the central vestibule which is where I presume the capacitor has to go.

 

I'd welcome responses from anyone who has fitted a sound decoder into this railbus model.

 

Many thanks.

[Ray H]

Oops, red faced department and a reminder not to have too many jobs on the go at the same time!

 

I re-read the article in Hornby Magazine about fitting sound to one of the other Heljan railbuses and realised that I'd need a sugar cube speaker. I placed an on-line order and then something said to me that I had one laying around. Not only did I find said speaker but it was attached to a Zimo MX644 21 pin decoder (with added stay alive capacitor) that I'd bought from Digitrains late last year for the Heljan railbus!

 

The MX645 that I thought was the decoder to use was bought even earlier and intended for an O gauge Derby Lightweight railbus and which as you've probably guessed still hasn't been fitted.

 

I've just fitted the 21 pin decoder (together with an [analogue] driver and a few seated passengers) to the (Heljan) railbus and given it a quick spin. It sounds good. Re-assembly later today.

 

Apologies for any inconvenience caused by the erroneous post.

[Oldddudders]

Oops, red faced department and a reminder not to have too many jobs on the go at the same time!

 

I re-read the article in Hornby Magazine about fitting sound to one of the other Heljan railbuses and realised that I'd need a sugar cube speaker. I placed an on-line order and then something said to me that I had one laying around. Not only did I find said speaker but it was attached to a Zimo MX644 21 pin decoder (with added stay alive capacitor) that I'd bought from Digitrains late last year for the Heljan railbus!

 

The MX645 that I thought was the decoder to use was bought even earlier and intended for an O gauge Derby Lightweight railbus and which as you've probably guessed still hasn't been fitted.

 

I've just fitted the 21 pin decoder (together with an [analogue] driver and a few seated passengers) to the (Heljan) railbus and given it a quick spin. It sounds good. Re-assembly later today.

 

Apologies for any inconvenience caused by the erroneous post.

No apology needed. I think you had done the most difficult bit by getting the body off, from others' accounts. I have fitted DCC to many locos, and sound to quite a few, but locos that risk damage simply to gain entry scare me, I must admit.

[Ray H]

Ian

 

I managed to get some pieces of plastic between the body and the chassis so that the body clips were free from the chassis. These clips are where there are recesses in the chassis. I may have used plastic that was thicker than needed because the first time I still had to struggle to slide the body off the chassis. The body is as others have discovered, a very tight fit.

 

I've since removed the body a couple of further times and whilst not that free, it was easier on the subsequent occasions.

 

The fit is so tight that the sound is trapped within the confines of the body shell because there is no where (as supplied) for the sound to escape. The sound level is adequate with the body off.

 

The chassis block is solid and I'm a little adverse to drilling holes in it (and wouldn't know what size to drill if I did).

 

The body seems to be painted clear plastic so I can't see an easy way to create an open window for the sound to escape.

 

Has anyone managed to provide a way for the sound to escape and how did they do it?

[pauliebanger]

Ian

 

I managed to get some pieces of plastic between the body and the chassis so that the body clips were free from the chassis. These clips are where there are recesses in the chassis. I may have used plastic that was thicker than needed because the first time I still had to struggle to slide the body off the chassis. The body is as others have discovered, a very tight fit.

 

I've since removed the body a couple of further times and whilst not that free, it was easier on the subsequent occasions.

 

The fit is so tight that the sound is trapped within the confines of the body shell because there is no where (as supplied) for the sound to escape. The sound level is adequate with the body off.

 

The chassis block is solid and I'm a little adverse to drilling holes in it (and wouldn't know what size to drill if I did).

 

The body seems to be painted clear plastic so I can't see an easy way to create an open window for the sound to escape.

 

Has anyone managed to provide a way for the sound to escape and how did they do it?

 

Ray,

 

The combination of sealed body and rows of seats acting as efficient dampers does adversely affect the total volume of sound. try setting the volume as high as possible. That could be with F key 28 if the sound project is equipped with Live Volume Control, or by increasing the value in CV266 to around 140.

 

Improvement beyond this is tricky. The underside is so exposed to view that migrating the speaker to a position below the floor, outside the body, is not a viable option.

 

You could drill out then file the driver's window so it's part or fully open. In which case the speaker might be better placed towards that end of the model, adjacent to the drivers cab.

 

Alternatively, as I have done with a couple, you could drill out then carefully file the two small vestibule windows opposite the speaker. This works quite well but as you have observed, the windows are integral to the bodyshell so modification will not be easilly reversible. It's not difficult, in fact I did this for another exhibitor's model during a show, but does require precision and a steady hand.

 

To finish it off, I painted the filed edge with the body colour to disguise the work done. It helped that this particular model was to be used on an end to end layout, so the side with the 'windows' removed could always be run on the blind side.

 

Kind regards,

 

Paul

[Ray H]

Paul

 

Thanks for the above. The speaker is opposite the cab at one end of the vehicle. It is currently metal side up but presumably it could be turned face down and a few small holes drilled through the chassis floor to allow the sound to escape instead of opening a window - I don't trust my filing!

[pauliebanger]

Paul

 

Thanks for the above. The speaker is opposite the cab at one end of the vehicle. It is currently metal side up but presumably it could be turned face down and a few small holes drilled through the chassis floor to allow the sound to escape instead of opening a window - I don't trust my filing!

 

Ray,

 

Really testing my memory here....

 

I think you might have a problem with wiring under the saloon floor if drilling through. Make sure you check this out before starting work.

 

Kind regards,

 

Paul

[Ray H]

Paul

 

Thanks. I did think that the end looked clear but have subsequently realised that the wiring for the marker lights must be somewhere in that area so maybe I'll steer clear of drilling there.

 

The underside of one end of the railbus is much clearer than the other and Jeremy at Digitrains - with whom I happened to be in communication - mentioned that he'd managed to fit a speaker in that area.

 

The sugar cube speaker that I order unnecessarily - I found the original after I ordered the replacement! - comes in two part, enclosure and speaker. I was going to investigate removing the back of the enclosure/mount and use the underside of the chassis as the replacement and see what it looks/sounds like. Do you know what effect it would it have on the sound generated if I reduced the depth of the enclosure/mount to a minimum, effectively fixing the speaker direct to the underside of the chassis and making sure it was sealed all on the sides and ends?

[pauliebanger]

Paul

 

Thanks. I did think that the end looked clear but have subsequently realised that the wiring for the marker lights must be somewhere in that area so maybe I'll steer clear of drilling there.

 

The underside of one end of the railbus is much clearer than the other and Jeremy at Digitrains - with whom I happened to be in communication - mentioned that he'd managed to fit a speaker in that area.

 

The sugar cube speaker that I order unnecessarily - I found the original after I ordered the replacement! - comes in two part, enclosure and speaker. I was going to investigate removing the back of the enclosure/mount and use the underside of the chassis as the replacement and see what it looks/sounds like. Do you know what effect it would it have on the sound generated if I reduced the depth of the enclosure/mount to a minimum, effectively fixing the speaker direct to the underside of the chassis and making sure it was sealed all on the sides and ends?

 

Ray,

 

That's an interesting thought. Providing there is a good seal, these speakers can produce a reasonable volume even with a flat plate fitted. The volume is not as high as with a proper box, but may well be louder than from an enclosure fitted speaker inside a virtually sealed body.

 

You could always try adding the one outside to the one you have fitted inboard, wired in parallel.

 

Still not sure about the aesthetics of an underslung speaker though. It's pretty exposed under there and the prototype is devoid of valences used on other railbus types which would help to disguise its presence.

 

Kind regards,

 

Paul

[Ray H]

Paul

 

Thanks for that clarification. I'll try and give the cut down version a go over the weekend if I can find a way to get the wiring from above ground to below ground, so to speak, without causing too much dis-configuration.

 

I'll try to take a picture to show what it looks like. I suppose as a temporary measure I could simply put some blue tack on the underside of the chassis to start with and press the speaker into that to see what degree of change it generates. I could then experiment with some plasticard strips to form the equivalent of a shallower enclosure. I think there may even be room to make the "enclosure" of such a size that I can still provide a shallow air space behind the speaker with the sides deep enough for the speaker to sit inside, rather than perched on the sides.

[Ray H]

Installation - Speaker 1.

 

The plan to use the extra speaker soon bit the dust due to my lack of understanding of how sugar cube speakers appear to work!

 

To start with, the speaker having been supplied separately from its mount/enclosure, I soon managed to dislodge the film cover from what I thought was (and maybe is) the back of the speaker. It never occurred to me that this film was an integral part of the speaker - I thought it was simply a piece of packing!

 

Secondly, I thought that because one face of the speaker is enclosed, the other side must be where the sound comes out. Why shouldn't it be?

 

Consequently, and in keeping with my idea of minimising the depth of the speaker, I discarded the aforementioned film, liberally covered what I thought was the back of the speaker with blu-tac and pressed it on to the underside of the chassis leaving the electrical connections to the speaker on the exposed side.

 

I turned on the sound on the railbus, cranked up the speed and . . . movement, but no sound (or no discernible sound as it turned out). Oops, that's blown the speaker or possibly damaged the decoder, thinks I.

 

The next trick was to remove the speaker from the chassis and try again. There was something discernible there but even my NHS hearing aids could only just hear it. I removed the blu-tac and the sound improved very (very) slightly. However, it was whilst removing the blu-tac that I realised that the earlier discarding of the film had been my mistake because adding the blu-tac had now terminally damaged the construction of the speaker - or at least that's the way I see it.

 

Fortunately, I managed to separate speaker 2 - the original - from its supplied enclosure and make a fresh start.

[Ray H]

Installation - Speaker 2.

 

It was back to the original plan, which was to remove the supplied enclosure/mount and replace it with something less deep. At least I now knew that the face of the speaker facing into the enclosure/mount played a significant role in the speaker making any sound.

 

The fist attempt at a replacement mount was made using 3mm strips of plasticard to make a frame, thereby separating the speaker face from the chassis by that amount. I applied a thin roll of blu-tac around both top and bottom edges of the frame and pressed it onto the chassis, connected the wires and tried it. Success - after a fashion.

 

 

I could here sound but it wasn't very loud albeit better (by not much) than with the speaker inside the vehicle.

 

A rumble through my box of odd speakers revealed one of a more conventional design. I duly covered the rear of this with blu-tac, pressed it into place and tried again. The result still didn't provide the sound level I was h0ping for and it didn't look pretty no matter which way round it was placed. That said, it provided by far the shallowest depth of the results my trials obtained.

 

 

 

 

It was back to plan whatever and the original sugar cube speaker.

 

I must have woken from a trance or something around this time because it suddenly dawned on me that the reason why the sugar cube speaker enclosures/mounts are the depth they are is probably because anything shallower doesn't produce the maximum sound that's possible from the speaker.

 

Out with the plasticard strip again, but this time using 4.1mm strips to make my frame. Blu-tac was again placed on both edges and the frame pressed onto the chassis. The wires once again connected and the railbus tried! Success - or, at least, a much louder sound.

 

I also discovered that by pressing the speaker more firmly onto the frame and thus the frame more firmly onto the chassis I could get a further increase in the sound level. It's still not perfect and that may be because the blu-tac isn't making a perfect seal, but I now have what I consider to be an acceptable sound level and the protrusion under the chassis isn't too bad.

 

 

 

It may not be prototypical but then neither is a (plastic) driver - with legs snipped off above the knee - who resolutely refuses to move even when the vehicle is going on the opposite direction to that which he's facing.

 

At least I had an opportunity to add a couple of (sawn-off) passengers to the inside of the railbus whilst the body was off - and they don't seem to want to alight either and I think I now understand a little better how sugar cub speakers work.