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General => Douglas Motorcycles - General Discussion => Topic started by: Red on 25 Apr 2020 at 09:37

Title: Aero Speedo
Post by: Red on 25 Apr 2020 at 09:37
Aero Speedo
My Aero was fitted with a period looking speedo, but as an instrument to measure speed it was absolutely useless. To buy a suitable replacement would have involved several hundreds of pounds and being tight I wasnít prepared to spend that amount of money. I had seen these replica Smiths Chronometric speedos on eBay from India for just over £20 so I thought I would buy one and have a play around trying to fit it. As you can see from the attached photos the end result in my opinion looks quite good and is accurate when measured against our local 30 mph speed warning camera. I had to get a speedo cable made up as the connection to the back of the speedo head is 18mm and not the usual 12mm. Cost of the cable was £12. I know the purists amongst us may cringe, but for an outlay of £32 I am more than happy. The same arrangement is now also fitted to my sonís Aero 500 
Title: Re: Aero Speedo
Post by: eddie on 25 Apr 2020 at 10:47
To add a note of warning!
 
           Original Chronometric speedos - and I presume, the replica ones - require a 2:1 drive when used in conjunction with 3.25/3.50 x 19" tyres. (It looks as if Roy has also fitted a Smiths speedo drive to his front wheel). If you have an original Douglas speedo drive, that has a different ratio (something like 29/10), so cannot easily be used to drive modern speedo heads.

   Regards,
                   Eddie.
Title: Re: Aero Speedo
Post by: Red on 25 Apr 2020 at 11:05
Hi Eddie

Yes you are right the replica speedos are the same 2:1 drive.

Roy
Title: Re: Aero Speedo
Post by: Aero on 27 Apr 2020 at 20:55
Hi Roy,
does the Smiths speedo drive need much modification to mate up to the Douglas hub?
Regards,
Mark
Title: Re: Aero Speedo
Post by: Red on 28 Apr 2020 at 09:33
Hi Mark

All you need to do is to file a couple of slots in the front wheel hub to take the two dog drives. You also need to do away with the cup over the front wheel bearing adjuster nut as this prevents the speedo drive from being fitted. Then use a few washers to pack it all out. In my case I turned up a stepped washer as the hole in the speedo drive was a larger diameter than the wheel spindle. I also made up a thin 7/16th left hand threaded nut to keep it all in place. Hope that makes sense. The speedo cable was made up by Speedograph Richfield - www.speedographrichfield.com

Roy
Title: Re: Aero Speedo
Post by: Aero on 30 Apr 2020 at 12:26
Thanks Roy,
I'll get one on order as my bikes never had the luxury of a speedometer.
Its also missing the cups over the bearing adjusters so the speedo drive will fill the space nicely.
If anyone has a spare cup I could use on my rear wheel I'd be interested in purchasing it, or any ideas as what would make a good substitute?
Title: Re: Aero Speedo
Post by: Red on 30 Apr 2020 at 15:21
Hi Mark

Be careful there are various types for sale. Some would be OK in a housing (like the Dragonfly) but not exposed as fitted to a lot of bikes and the way you would want to fit it on the Aero. Some also have the solid white line at 40mph and not 30mph?? The link below is for the ones I bought. Have now gone up to the princely sum of £21.73. That's inflation for you.

Roy

https://www.ebay.co.uk/itm/0-80-Mph-SMITHS-SPEEDOMETER-BIKE-80mm-DIAMETER-BODY-REPLICA-INCLUDE-O-RING-BULB/132657886266?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
Title: Re: Aero Speedo
Post by: Tazmantic on 30 Apr 2020 at 21:53
Hi this is really interesting as im trying to get the speedo correct on my 250, does the speedo you bought come with the mounting bracket? and where did you get the speedo drive from?

Many thanks Neil
Title: Re: Aero Speedo
Post by: Red on 01 May 2020 at 09:05
Hi Neil

If you click on the link in my previous post this will take you to the eBay page from where I purchased the speedos. No they don't come with a bracket. That was made from some scrap sheet alloy I had under the bench. The speedo drive is a standard Smiths item used on any number of bikes back in the 60's, including all the post war Douglas models, but if you can't get hold of one you can find replica ones on eBay, again from India, at a sensible price.

Roy
Title: Re: Aero Speedo
Post by: Tazmantic on 01 May 2020 at 09:34
Hi Roy,

Yes already watching the speedo on ebay thanks (does yours have the pilot lamp? have you connected it)  tho 80mph is very optimistic on a 250  :lol: ok that's great thanks for the info so I presume any smiths 2-1 ratio drive will do? My front wheel has a cap on it I presume this just needs removing and the few mods doing you have already spoke about.

Cheers Neil
Title: Re: Aero Speedo
Post by: Red on 01 May 2020 at 10:09
Hi Neil

Yes it does have a pilot light and yes I did connect, although frankly I am unlikely to ride the bike in the dark. There are two coloured wires from the bulb holder which wouldn't look right. The earth wire I cut right back almost to the bulb holder and then cut a slot in the edge of the rubber surround and turned and soldered the wire to the metal part of the bulb holder. When fitted back into the speedo that wire can no longer be seen and the earth is provided through the case of the speedo, bracket etc. The other coloured wire I replaced with a black wire and then connected it in to the pilot light bulb circuit in the headlight.

Roy
Title: Re: Aero Speedo
Post by: Tazmantic on 01 May 2020 at 10:16
Hi Roy,

Many thanks for the info just found this shame its the wrong mounting really and 120mph..

https://www.ebay.co.uk/itm/SMITHS-SPEEDOMETER-KIT-120M-WITH-CABLE-AND-HEAVY-DUTY-METAL-DRIVE/201129067209?hash=item2ed43a02c9:g:jhIAAOSwZtJW~AIm

Cheers Neil
Title: Re: Aero Speedo
Post by: Tazmantic on 01 May 2020 at 10:51
but found this..

https://www.ebay.co.uk/itm/SMITHS-SPEEDOMETER-80M-WITH-CABLE-METAL-DRIVE-ROYAL-ENFIELD-BSA-NORTON-REPLICA/191612959109?epid=865518485&hash=item2c9d05b985:g:lDoAAOSw9N1Vjokr
Title: Re: Aero Speedo
Post by: Red on 01 May 2020 at 14:06
Hi Neil

Good price but the body of the speedo is wrong for one that is going to be mounted on a simple bracket. If it was housed in the headlamp unit like a Dragonfly then it would look OK. Only my opinion. The choice is down to you.

Roy
Title: Re: Aero Speedo
Post by: Tazmantic on 02 May 2020 at 10:18
Hi Roy,

Yes that's exactly what I thought, shame they don't do the one like you bought in a kit.

Cheers Neil
Title: Re: Aero Speedo
Post by: Tazmantic on 27 Jun 2020 at 11:27
Hi again, would this speedo drive be ok??

https://www.ebay.co.uk/itm/SPEEDO-DRIVE-2-1-RATIO-ROYAL-ENFIELD-BSA-NORTON-ETC-BRAND-NEW/332679608785?hash=item4d753ff9d1:g:lCkAAOSwm8NbGoup
Title: Re: Aero Speedo
Post by: Red on 27 Jun 2020 at 11:36
Hi Neil

Should be. It is just a straight copy of the Smith's speedo drive with a 2:1 ratio

Roy
Title: Re: Aero Speedo
Post by: Tazmantic on 27 Jun 2020 at 14:15
Thanks Roy  :lol: