F: Frame Vincent HRD Rapide (B) from 1948. Max allowed weight and axle loads

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tom_vincent_rapide

Forum User
Non-VOC Member
Hello everybody. I am new to this forum. Graham (webmaster of this forum) suggested to post the question on this forum and hopefully someone will know the answer. Apologies if I posted this thread in the wrong section. I have a Vincent HRD Rapide (B series) from 1948 and recently I took it for a so called vehicle safety test in order to register it and be able to finally start riding it legally on the roads. However, at the test center they told me that I need to give them some additional information like what is the maximum allowed weight my machine can take (I assume that this is something like motorbike+rider+luggage etc), but also information if possible what is the max allowed load on each axle (front and rear). I couldn't find that information anywhere online. All docs and tech information available is just basically engine details, tyre sizes and info about dry weight of this motorbike, but nothing about what is/was the max weight of the load. Does anybody nowadays will even know that information, especially that motorbike is from 1948? I have the VOC certificate for this machine issues back in December 2017, but unfortunately it didn't come with much additional technical information.

If its possible, could you please post what is the approx max allowed weight Vincent HRD can take and/or what is the max allowed load for each axle? With that info, I will be able to start riding this great machine and finally register it! Kind regards and many thanks for any help in the above matter, Tom.
 
bmetcalf

bmetcalf

Well Known and Active Forum User
VOC Member
Do the authorities require a document to confirm the maximum loads? Would the bike ever get weighed by the authorities under each tire to see if you have overloaded it? Do you plan to ride it by yourself or loaded for a trip to Portugal with wife/girlfriend (not both o_O )?

According to this https://en.wikipedia.org/wiki/BMW_/5_motorcycles, these bikes can carry 418 lbs/190 kg in weight. This is probably as old a bike that has that data available and is pretty comparable.

Maybe Bananaman can tell us if he has weighed his bike with passengers and luggage?
 
Simon Dinsdale

Simon Dinsdale

VOC Machine Registrar
VOC Member
VOC Forum Moderator
In the back of the riders handbook it has some performance figures and dry weight is listed but I have never seen any official factory figures for max allowed weight or weight on each axle. I suspect such figures were never considered in 1948 and are a modern requirement characteristic. Certainly not required when registering a Vincent in the UK.
Rider HB.jpg
 
vibrac

vibrac

Well Known and Active Forum User
VOC Member
I would suggest that taper rollers would make bikes with roller bearings wimps when it came to max axel loads, after all taper bearings are invariably specked for trailers. and since that covers the triangulated RFM and the alloy beam Girdraulics I would find max load for the tyres and quote that.
It does seem a ridiculous stipulation like the wattage of an acetylene lamp how would you find the official figures if they were never issued
 
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oexing

Well Known and Active Forum User
VOC Member
Same requirement for Germany, you need the gross weight in vehicle papers plus the empty weight - which you could provide from placing the bike on scales. Maybe one of my countrymen would add a photo of his bike´s paper here ? There is certainly a limit from tire max. loads so check your tires as well.

Vic
 
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timetraveller

Well Known and Active Forum User
VOC Member
Hi Tom, the following are not official figures from the time that your Vincent was manufactured as no such numbers were ever required to be produced in the years in which Vincent motorcycles were manufactured. However, here are some values which have been shown to be safe over the last 70+ years on a variety of roads and conditions.

The weight of a Vincent twin motorcycle when new was about 204 kg, dry weight, no passengers, or luggage. This weight is distributed approximately equally between the front and rear axles. So let us say that there was about 102 kg on each axle. Add fuel and oil, both tanks full and this adds about an additional 20 kg which is also roughly distributed equally between the front and rear axles. This gives approximately 112 kg per axle. Now add a rider of 100 kg. Most of his weight is in front of the rear axle and is taken by the front axle so let us say that the front axle now has 192 kg of load. If one adds a pillion passenger of up to 100 kg then that adds almost all that weight to just the rear axle and many bikes carried another 100 kg of luggage on camping trips so the rear axle could withstand a total of over 300 kgs of weight with complete safety and for many years of use. The front axle does not experience much of the weight from the rear of the bike until one uses the brakes hard. Then most of the weight of the bike, riders, luggage, and fuel can be transferred to the front of the bike. It would be unusual to get the rear wheel of such a heavily loaded bike off the ground but certainly over 80% of the total weight would be experienced by the front axle (204+20+200+rider [100]) gives about 400 kg on the front axle. When one considers that many people fitted large sidecars to these bike then the above figures are not the maximum which will have been shown empirically over many decades to be safe.

There is an alternative way to try to estimate the loads. I supply a modified front steering stem complete with springs. These springs were developed, after calculation, by road testing to give comfortable suspension. For twin cylinder Vincents with medium weight riders I provide 36 lbs/inch springs with 3 inches of preload to give a further three inches of movement. Two springs multiplied by 6 x 36 gives 432 lbs = 196 kg. For 100 kg riders I provide 45 lbs/inch springs with 2 inches of preload and three inches of movement to give 450 lbs = 204 kgs. 105 kg riders require an extra 12 mm of compression giving an extra 45 lbs/20 kgs.

Note that the whole of the front wheel, suspension, mudguard and stays, headlamp and stays etc. are all unsprung so some of their weight has to be added to the load on the front axle.

I do not know how best one can influence the administrative mind but if none of the above helps then perhaps you can look up the sheer strength of 16 mm diameter steel bar and point out that these axles have been in use for over seventy years and are not known to break.

Good luck with it.
 
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