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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 25th Jul 2004, 5:06 pm   #1
Rod H
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Default R1155 Slow Motion Drive.

I have recently acquired, via ebay, a rather tatty R1155A. Apart from missing its DF section and Jones plugs, the rest of the set is fairly complete, but in need of much refurbishment. This is the first bit of military kit I've purchased with the view to restoration and I have to say I'm really relishing the challenge!

However, my set appears to be missing a component somewhere in the slow motion tuning drive, with the result that the large (outer) tuning knob isn't engaging with anything and merely freewheels. From what I can gather, the set has the original type of drive assembly (rather than the later and improved version).

Having removed the small (inner) knob, and the star shaped spring beneath it, the larger knob simply lifts straight off. I image that beneath this knob should be some form of epicyclic gear arrangement, but the only parts fitted are a cork washer, a thin metal disc and three roller bearings (the latter fitted into hollows in the knob).

As I'm still learning my way around these sets, I'd be extremely grateful if anyone more familiar with them could provide a detailed description of the missing part. Whatever the part was, it must have been extremely small given the limited space available beneath the knob.

However, I do not underestimate my chances of ever finding a scrap replacement, and I can envisage that I might well have to improvise or fabricate a suitable component. So, to that end, the more detailed the description that can be provided the better (a sketch or close-up photo would be ideal). Also, what is the correct reduction ratio for this mechanism?

All information gratefully received. Many thanks.

Rod H

Last edited by Station X; 1st Mar 2005 at 9:00 pm. Reason: Moved to Archive Section.
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Old 25th Jul 2004, 5:53 pm   #2
Chris_C
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Default Re: R1155 Slow Motion Drive.

Hi Rod

I have a set of the tuning mechanism which, if I remember correctly, is from an R1155.

It is exactly as you describe with the 3 cone shaped rollers. It's pretty dirty and unloved at present. It has several Gov't numbers on it, the small knob is 10A 14447 and the large knob 10A 14448.
Does this sound familiar??

If it was all cleaned up then it should act as a slow motion drive.

Cheers
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Last edited by Station X; 1st Mar 2005 at 9:14 pm.
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Old 25th Jul 2004, 7:18 pm   #3
jim_beacon
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Default Re: R1155 Slow Motion Drive

Rod,

the drive you have is correct and complete. As Chris says, it needs to be very clean and lighlty lubricated. you may have to move the smaller knob back and forth a bit to get the drive to work smoothly without eithre binding or slipping (this is why the drive was replaced with the later geared type).

Jim.

Last edited by Station X; 1st Mar 2005 at 9:15 pm.
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Old 25th Jul 2004, 9:40 pm   #4
JHGibson
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Default Re: R1155 Slow Motion Drive.

Hi Rod,
I have a R1155A so I took a look at the slow motion mechanism. It seems that all you are missing is a plain 3/8 in dia washer between the star spring and the small knob. This washers purpose is to compress the star spring so that friction can be generated between the taper rollers and the springy disc.
The slow motion ratio must be about 200 to 1. The pointer moves about 3 times its own width for one turn of the large knob.
The shaft the small knob goes on is the direct drive to the tuning cap. If you try to turn it with the small knob removed, you will only feel the friction of grease packed ball bearings, so make sure it turns freely before working on the drive.

John.

Last edited by Station X; 1st Mar 2005 at 9:16 pm.
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Old 25th Jul 2004, 10:39 pm   #5
Rod H
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Default Re: R1155 Slow Motion Drive.

Thanks to all for the responses. It seems I may have got unnecessarily concerned, and it's pleasing to know that I'm not missing a part after all.

It looks, therefore, that it's just a case of getting everything cleaned, greased and correctly adjusted, ensuring that I've also got a 3/8 washer in place. I'll give it a go and see how I get on.

Rod H

Last edited by Station X; 1st Mar 2005 at 9:16 pm.
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Old 25th Jul 2004, 11:43 pm   #6
Rod H
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Default Re: R1155 Slow Motion Drive

Just to close the chapter.

After having cleaned, lightly greased and carefully adjusted the mechanism everything is now working fine and I can sleep in peace. I could never have believed a slow motion drive could work in such a crude fashion!

Thanks again to all for the advice. Now it's back to the real fun part of restoring the chassis.

Rod H

Last edited by Station X; 1st Mar 2005 at 9:17 pm. Reason: Move to Archive Section
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Old 26th Jul 2004, 9:30 am   #7
joe
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Default Re: R1155 Slow Motion Drive.

Hi Rod

I'm glad that you've got it going; I was going to offer you some cork sheeting which I got for mine since the magic washer was missing from it. Its difficult to see why it works but I think it depends on the fact that the three rollers are not cylindrical but slightly conical.

Joe

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Old 30th Jul 2004, 1:18 pm   #8
RobinBirch
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Default Re: R1155 Slow Motion Drive

Hi,
If it slips every so often you may find that replacing the ordinary grease with kilopoise grease will help. This will make the drive slightly stiffer and higher friction so the surfaces won't slide and the rollers will roll.

Robin

Last edited by Station X; 1st Mar 2005 at 9:18 pm.
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Old 7th Aug 2004, 5:02 pm   #9
JHGibson
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Default Re: R1155 Slow Motion Drive.

Actually the concentric knob slow motion drive on the R1155A worked perfectly. The reason for the change to the geared type drive was that at the planes cruising altitude, the ambient temp was way below zero and the radio op had to wear heavy gloves. The gloves made the op's hands clumsy and he had great difficulty in grabbing just one of the concentric knobs.
John.

Last edited by Station X; 1st Mar 2005 at 9:19 pm.
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