Latest topics
» Vale Onslow parts on ebay
Yesterday at 8:09 pm by davin999

» Miller Switch for Cruiser
Thu Dec 13, 2018 8:50 pm by kerabo

» Re-register Cruiser/Falcon
Thu Dec 13, 2018 7:06 pm by peter@dunfordconstruction

» Petrol tanks and spares
Wed Dec 12, 2018 6:37 pm by piston 197

» Cruiser 80 speedo
Wed Dec 12, 2018 5:15 pm by piston 197

» Items wanted
Wed Dec 12, 2018 5:14 pm by piston 197

» Wheel bearings anyone?
Wed Dec 12, 2018 4:55 pm by piston 197

» 1936 Cruiser wiring
Wed Dec 12, 2018 12:34 pm by kerabo

» 1925 350cc fanny b
Tue Dec 11, 2018 6:14 pm by keith.hodgenia


New Smiths 80mph speedos

Go down

New Smiths 80mph speedos

Post  John Wakefield on Sat Dec 09, 2017 11:49 am


John Wakefield

Posts : 87
Join date : 2017-08-31

Back to top Go down

Speed

Post  kerabo on Sat Dec 09, 2017 1:20 pm

The build is ok but they have a metric thread for the cable at the head end. I fitted a head a cable and a drive but it's way out in the speed. It could be close if it was KMs
Even so it's a cheap way out if you could remark your speedo.
The drive is the same as the smiths but mine was very tight to tighten on the thread. I also had to trim the tags that locate in the wheel slots before they would fit.

Ken
avatar
kerabo

Posts : 2523
Join date : 2008-02-11
Age : 68
Location : Falcon 87..1936 Cruiser 39. Falcon 81 Green Lane bitsa. Sunbeam S8. Honda Deuville.

Back to top Go down

Re: New Smiths 80mph speedos

Post  John Wakefield on Sat Dec 09, 2017 1:52 pm

Be OK for someone who was only showing a bike, no mention of cable and drive gearbox in this advert. Probably a km one with mph dial.

John Wakefield

Posts : 87
Join date : 2017-08-31

Back to top Go down

Speedo

Post  kerabo on Sat Dec 09, 2017 2:36 pm

See the close up of the thread on the head.
You could adapt it

Ken
avatar
kerabo

Posts : 2523
Join date : 2008-02-11
Age : 68
Location : Falcon 87..1936 Cruiser 39. Falcon 81 Green Lane bitsa. Sunbeam S8. Honda Deuville.

Back to top Go down

Smiths speedo head

Post  FB vincent on Sat Dec 09, 2017 3:34 pm

I think you will find that a genuine Smiths magnetic speedometer head from a later 18" wheel diameter FB will be marked SN3153/XX, followed by the numerals 1664 indicating the correct gear ratio. Perhaps others have a full listing of the Smiths codes. Sandy

FB vincent

Posts : 669
Join date : 2009-01-20
Location : Hertfordshire

Back to top Go down

Speedo

Post  kerabo on Sat Dec 09, 2017 3:44 pm

When you think about it an 18" wheel is an 18" wheel and the Speedo should read the same if it's on a royal Enfield or a Francis Barnett if like I did use the drive supplied.

Anyway a cheap alternative depending on what you need. I intend to remark my numbers when I get round to it.
Regards Ken
avatar
kerabo

Posts : 2523
Join date : 2008-02-11
Age : 68
Location : Falcon 87..1936 Cruiser 39. Falcon 81 Green Lane bitsa. Sunbeam S8. Honda Deuville.

Back to top Go down

Re: New Smiths 80mph speedos

Post  John Wakefield on Sat Dec 09, 2017 8:43 pm

Here is a formula for calculating the gear ratio number for the Smiths Speedos from The Classic Motorcycle March 1994 (wont help with this Indian †made instrument as it has no gearing number)

To calculate the correct gearing number there is a formula to calculate turns per mile (TPM) for a given bike.
TPM = 1680 x N divided by R
N = number of turns of speedo cable to 6 turns of wheel & R = Radius of wheel/tyre in inches.
After calculation you should get a number in the 1600 series. It needs to be within 35.

John Wakefield

Posts : 87
Join date : 2017-08-31

Back to top Go down

When you think about it

Post  piston 197 on Sun Dec 10, 2017 7:10 am

[quote="kerabo"]When you think about it an 18" wheel is an 18" wheel and the Speedo should read the same if it's on a royal Enfield or a Francis Barnett if like I did use the drive supplied.



While i agree in principle a 18" wheel fitted with a 400 x 18 trials tyre and one fitted with a road going 3.25 x 18 will have entirely different circumferences, which is why Smiths gave different revs per mile figures based on tyre circumference rather than wheel size, and also directional rotation of drive ,ratio and type of speedo head ( magnetic,chrono anti-clock and clockwise )

It is not as straightfoward as you think to arrive at an accurate speedo reading.

The Indians just ignore this and build a cheap one fits all solution, it is what it is , a cheap imitation which looks the part, is a lottery with regards to accuracy, is similar, but you get what you pay for !
avatar
piston 197
Moderator

Posts : 4166
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Re: New Smiths 80mph speedos

Post  John Wakefield on Sun Dec 10, 2017 8:50 am

These speedos were never accurate when originally fitted, on my Greeves for example the speedo reads 10 mph fast despite having the original speedo head with correct gearing number as listed by Smiths and original hub drive gear. Although Smiths made them to suit different gear ratios (the 1600 series number) I think a lot of manufacturers particularly Greeves (who used it on trials & road bikes) just bought one ratio to suit all. †Over reading was a bonus for sales as it gave the impression that the bike was faster than it actually was.
Another factor that effects accuracy is on Villiers 2T 3T 4T 1H & 2H engines that have a speedo drive from top of gear box. Some manufacturers used this but others like Greeves used an angle drive unit in rear hub. The gearbox set up was dependent on what gearbox/rear sprockets are used. I have fitted one of the cheap cycle digital speedos which gives a very accurate reading, not only speed but distance. These of course are calibrated from the actual rolling circumference of the tyre.


Last edited by John Wakefield on Mon Dec 11, 2017 5:38 pm; edited 1 time in total (Reason for editing : 1H & 2H engines added)

John Wakefield

Posts : 87
Join date : 2017-08-31

Back to top Go down

agree to disagree

Post  piston 197 on Sun Dec 10, 2017 9:09 am

Whereas i agree with some of what you say, Smiths made the best effort based on final gearing, type of tyre size, ,sprocket size etc.
for example in 1959 FB used
SN3103/55 on Plover 78 and Light cruiser 79
SN3103/20 on Falcon 81
SN3103/55 on Cruiser 80 and 84
SC1102/06 on Trials model 83

now you don't have to be a genius to work out that tyre diameters on the common models i.e 80/84 and 78/79 will be the same and use the same instrument, and the 83 will use a 400 trials tyre

they made the best effort to supply an accurate instrument and the motorcycle manufacturers to use an accurate instrument, now if some numpty fitted different sprocket sizes or non standard wheel diameter/tyre sizes, that is their fault not the manufacturers.
The police continued to use chronometric speedos on some of their bikes instead of magnetic as they claimed greater accuracy, but in conversation with a speedo specialist , he has categorically told me that he can get more accurate calibration on magnetic instruments than on chronos ?

My van reads about 4MPH different to the sat nav at the moment, it is a lot more accurate when i fit new rear tyres ( it is rear wheel drive)

If your speedo is that inaccurate i suggest you
1 check all gearing and tyre size
2 check it is the correct head ( i can supply info)
3 get it calibrated to correct the revs per mile reading
JH
avatar
piston 197
Moderator

Posts : 4166
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Speedo

Post  kerabo on Sun Dec 10, 2017 2:37 pm

Slightly of the motorcycle question but I worked on trucks all my working life. Every 2 years the Tachometer has to be checked and calibrated. They are set to exact to 90kph about 56mph so you may wonder why some trucks are faster than others.
The smaller contractors have a set of tyres to fit just for calibrating. These will have been worn down regroved and worn down again, so just legal. This gives about 18" per revolution less than a new tyre. So calibrate it with these worn tyres and then fit good tyres and in your a couple of mph up.
Ken
avatar
kerabo

Posts : 2523
Join date : 2008-02-11
Age : 68
Location : Falcon 87..1936 Cruiser 39. Falcon 81 Green Lane bitsa. Sunbeam S8. Honda Deuville.

Back to top Go down

Re: New Smiths 80mph speedos

Post  John Wakefield on Sun Dec 10, 2017 4:02 pm

piston 197 wrote:Whereas i agree with some of what you say, Smiths made the best effort based on final gearing, type of tyre size, ,sprocket size etc.
for example in 1959 FB used
SN3103/55 on Plover 78 and Light cruiser 79
SN3103/20 on Falcon 81
SN3103/55 on Cruiser 80 and 84
SC1102/06 on Trials model 83

now you don't have to be a genius to work out that tyre diameters on the common models i.e 80/84 and 78/79 will be the same and use the same instrument, †and the 83 will use a 400 trials tyre

they made the best effort to supply an accurate instrument and the motorcycle manufacturers to use an accurate instrument, now if some numpty fitted different sprocket sizes or non standard wheel diameter/tyre sizes, that is their fault not the manufacturers.
The police continued to use chronometric speedos on some of their bikes instead of magnetic as they claimed greater accuracy, but in conversation with a speedo specialist , he has categorically told me that he can get more accurate calibration on magnetic instruments than on chronos ?

My van reads about 4MPH different to the sat nav at the moment, it is a lot more accurate when i fit new rear tyres †( it is rear wheel drive)

If your speedo is that inaccurate i suggest you
1 check all gearing and tyre size
2 check it is the correct head ( i can supply info)
3 get it calibrated to correct the revs per mile reading
JH

Quite so John and I am sure in the case of FB & James with their high levels of production they obtained the correct speedo for each model. But some of the smaller manufacturers like Greeves, whos main output was trials & scramble bikes, would have fitted the same speedo on the small number of roadsters, thus keeping cost down by buying larger batches of one type & not having to stock different types. As you say accuracy down to tyre size. 400 x 18 on trials bikes & 325 x 18 on roadsters.

John Wakefield

Posts : 87
Join date : 2017-08-31

Back to top Go down

Greeves speedos

Post  piston 197 on Sun Dec 10, 2017 4:17 pm

Greeves also used many different speedos relevant to models/wheel size/tyre sizes, i have all of the lists from 1954 to 1969 , so even a small manufacturer like Greeves tried to get the job done right, but when they offered rear sprockets for trials use, in different sizes, the accuracy of any instrument will be brought into question

If you have any need of this info give me the model and year and i can let you know which speedo head was originally specified.
i.e
1960 25DB SN3153/55
1961 25DC SN3153/55
1962 25DC SC1102/15
1963 25DC SN3170/09
1964 25DC SSM2001/00

now the change from 63 to 64 was to a grey faced SSM unit, but i would have money between 1960 and 1963 there was a wheel diameter, or gearing change necessitating a different instrument ?? so even a "Small" manufacturer like Greeves tried to keep up with accuracy ??
JH
avatar
piston 197
Moderator

Posts : 4166
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Re: New Smiths 80mph speedos

Post  John Wakefield on Sun Dec 10, 2017 4:32 pm

The speedo head on my 1965 East Coaster is SSM2001/00 †1600 (the 1600 is the gearing number, 1600 revs per mile) Rear drive is 2.1:1 turns of cable to 1 rev of wheel, tyre is 325 x 18. So speedo model is as per what you have quoted. BUT, the important thing is the gearing number. That does not appear on the printout I have of the Smiths catalogue. When Motor Cycle Mechanics tested the East Coaster in 1965 they quoted a top speed of 80MPH obviously from the speedo (not timed) and was the same 10MPH fast as with my bike. A 250cc Greeves with 4T will only do 70MPH tops.
To be accurate, using the formula published in The Classic Motorcycle & given earlier in this thread the speedo gearing number should be nearer 1714 so probably 1700 in round figures.
All Greeves Roadsters from 1959 onwards had 18 inch rear wheels with 3.25 tyres. But up to around 1963 they had the tin hub, and after the full width alloy hub. The hub gearing may have changed, but again its the speedo gearing number that is important.


Last edited by John Wakefield on Mon Dec 11, 2017 5:42 pm; edited 1 time in total (Reason for editing : Speedo number corrected)

John Wakefield

Posts : 87
Join date : 2017-08-31

Back to top Go down

Numbers

Post  piston 197 on Sun Dec 10, 2017 4:46 pm

You either have the wrong speedo head or have typed the info incorrectly
it should be SSM 2001/00 ( not SSM2001/100) ? Assuming your speedo head is calibrated correctly, your tyre profile is correct ,as per original fitment and your sprocket sizes are as per specification , then you have it as accurate as it ever was, any slight deviation and it will be reading erroneously , or always did in the day ?
The law govenring speedometers used to be " within 10% @ 30MPH" hence the law regarding exceeding the 30MPH speed limit USED to have a blind eye turned to it with regards a 3MPH over reading , this is now not the case, I recently attended a speed awareness course ( 34 in a 30 limit) but there were people there who had done between 31MPH and 43MPH in a 30 limit. There now seems to be a zero tolerance in some areas, so best get it fixed ?

JH
avatar
piston 197
Moderator

Posts : 4166
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Re: New Smiths 80mph speedos

Post  John Wakefield on Sun Dec 10, 2017 5:16 pm

Sorry a typo, mis-read the / (now corrected) Yes its SSM2001/00 and all as per original set up, sprocket wont effect it as drive is from rear hub. Its not really an issue but worth posting to give others an insight to these issues whatever type of bike they run.
As for fixing it yes, a cheap fix as i previously posted, †I fitted a cycle speedo and have marked correct 30MPH & 40MPH on the glass of the Smith speedo as a back up. Cheaper than buying another possibly equally inaccurate one from eBay at around £80.


Last edited by John Wakefield on Mon Dec 11, 2017 5:43 pm; edited 1 time in total

John Wakefield

Posts : 87
Join date : 2017-08-31

Back to top Go down

????????

Post  piston 197 on Sun Dec 10, 2017 5:26 pm

Yes FB on some cruiser models took the drive from the rear hub and some from the gearbox drive on The 1H was from the gearbox and the twins from the rear wheel mounted drive, presumably in an effort to aid accuracy ??
JH
avatar
piston 197
Moderator

Posts : 4166
Join date : 2008-08-17
Location : ross-on-wye

Back to top Go down

Re: New Smiths 80mph speedos

Post  Sponsored content


Sponsored content


Back to top Go down

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum