Misc: Everything Else Prototype of new AVO coilover for Series ‘D’ Vincents

[hadronuk]

I received this yesterday.

This new D unit uses the same basic components as the already well-proven B/C coilover units. So I am hopeful that testing will be straightforward and quite quick.
It should be a straight fit. Damping and preload are fully adjustable and there is a wide choice of springs. Default is likely to be 300 lb/inch with others available to order. The top mounting is a metalastic bush, the lower mounting is a spherical bearing.
There are no plans to fit a dust cover, although should a customer want to fit one they have sourced, this would be very easy as the spring can be changed without the need for a spring compressor. Looking back at my old notes, it seems very possible the dust cover from the original Armstrong unit may fit. I will try to check this.

QUESTION FOR D OWNERS: With the original unit, does rotation of the pins cause wear in the frame & RFM?
The idea is that the low friction spherical bearing will minimise this possibility, as well as overcoming any possible misalignment.

I discussed with AVO the problem some riders have with the high seat height of the D.
If it is specified at the point of order, during manufacture a "droop restrictor" spacer tube could be fitted internally on the damper rod. No other changes would be required as there is a large range of adjustment of the spring preload. If the coilover extension was reduced so that total travel of the units was the same as on the B/C units, D owners could still enjoy an excellent ride quality with a seat height reduced by about 1 3/4 inches. Although this spacer could be fitted/removed retrospectively, AVO are reluctant to do so, as ideally several components should be replaced when rebuilding units.

Stock items should be available about 3 weeks after prototype testing is completed.
Expressions of firm interest (to me) would be greatly appreciated, as AVO need to decide how many to make in the first batch.
Price is expected to be the same as the existing coilovers, so "£200 +VAT. Carriage UK £10 +VAT. Ireland £15 +VAT Rest of world please email for quote."
Extra springs (one for solo, one for two up touring?) are about £40 each, although experience with the B/C coilovers is that the adjustable preload and damping allows the default spring to cope with a very wide range of loads.

I will have this with me tomorrow at the VMCC Founders Day at Stanford Hall, should anyone want a look. Please visit our COVOC stand and ask for Rob.

 

[Peter Holmes]

Yes please Rob, the version that lowers the seat height for me, happy to start at 300lbs
Cheers Peter

 

[Bill Thomas]

Hello Rob, I went out on my "C" coilover the other day, Had the spring at 7 " Long, Pulled the rebound rubber
Away from the top, After a short ride, It had been pushed to the top, Now got the spring to 6,1/2". Not been out yet. With the old "D" I thought the springs we used were 380 to 400lb, Are you saying with the better damper, We need lower springs ?. Cheers Bill.

 

[timetraveller]

A few comments here and thanks for organising these new dampers. I wonder about the comments that the 'D' ride height is high. I don't think so and I am only 5'8". It is true that when the bike is on the centre stand there is a lot of height but there is also a lot of movement. My recollection is that there was intended to be about 7" of movement on the rear wheel, and like with the 'B's and 'C's, with a lot less potential movement, a lot of this was taken up by the rider sitting on the bike. When seated I never felt that I could not reach the floor. The adjustable pre-load with the new AVO damper will presumably take up some of that original movement caused by the rider loading. The way that I always check the springing on a 'D' is to have the bike on its wheels and then press down repeatedly on the front of the seat, roughly where one's behind would be when seated. The bike should more or less float up and down with equal movement on the front and the rear. I cannot quite imagine what is going to happen when the rear suspension is pre-loaded. Will the potential over movement, that which is normally provided by the rider's weight , be mimicked by the pre-load or not. It is going to be very interesting to see what happens on the road tests. Modern dampers are so much better than those of 64 years ago that there is real potential for improvement and we should thank hadronuk for his efforts here.
I cannot find the rate of the 'D' rear spring but I do know that a lot of riders fitted the sidecar version of the spring for use when the machine was used solo. The pre-load might take care of that. Once again the final tweaking can be done on the back of test rides.

 

[Bill Thomas]

I am just a bit worried the springs are a bit weak, And banging the rebound rubber won't do the unit any good ?. I am only one up on my "C", I am a bit more heavy than Eddy, Can't see how he gets away with it 2 up with luggage. Cheers Bill.

 

[timetraveller]

I forgot to answer Rob's question re. wear.

QUESTION FOR D OWNERS: With the original unit, does rotation of the pins cause wear in the frame & RFM?
The idea is that the low friction spherical bearing will minimise this possibility, as well as overcoming any possible misalignment.

I have never seen any sign of wear in either the top or bottom pivot holes. Remember that the pins were held in with circlips, not tightened up with nuts, so they could have rotated had they wished.

 

[hadronuk]

Hello Rob, I went out on my "C" coilover the other day, Had the spring at 7 " Long, Pulled the rebound rubber
Away from the top, After a short ride, It had been pushed to the top, Now got the spring to 6,1/2". Not been out yet. With the old "D" I thought the springs we used were 380 to 400lb, Are you saying with the better damper, We need lower springs ?. Cheers Bill.

By lower, I take it you mean lower spring rate? In short –yes. You are right that the original B/C springs together were about 390 lbs/inch and I gather the D usually used a 380 lbs/inch spring. However, the B/C setup was extraordinary because the shortness of the springs gave a substantial negative preload, so that very little of the available damper travel was used.

So within limits, more preload and better quality damping, both adjustable, undoubtedly allows softer springing, giving better comfort and grip.

The question of course is exactly how much softer?

It is a difficult decision, because it is an engineering and individual compromise between so many different factors. The weight of the rider, acceptable seat height, local roads, how fast you ride, how much bottoming out is acceptable, etc.

My decision to make 275lb/inch the default was perhaps a bit bold. The safe choice would have been, say 350 lbs/inch. But I felt that 275 would work for the majority of riders, who if saddled with a default 350 spring would be losing out somewhat on ride quality. Big Ed frequently uses his Rapide two up with the 275 spring and finds it is still acceptable.

Regarding your particular situation, the first thing I would say is that in my view if suspension never bottoms out it is too stiff. My local roads have some appalling bumps and pot holes to the extent it is just not possible to steer round all of them. A spring stiff enough to never bottom out would be far too stiff the rest of the time. I’ve tried it!

Checking my notes, it is not advisable to set the 275 spring preload to shorten the spring more than 6.625 inches unloaded. If you do, it is possible the spring may become coil bound before the bump stop fully does its job. If you find that is still insufficient, have you tried a modest increase in damping stiffness? If you want to try a stiffer spring they are available in increments of 25 lbs/inch. But step changes in wire size etc. means some have better closed lengths than others. Although 300 and 325 springs are available in this range, the next “sweet spot” is 350 lbs/inch.

Incidentally, I have found a cheap spring compressor on Ebay that makes changing springs an easy job. I will find a link if anyone is interested.

With regard to the D, the original setup is much better than the original B/C, as it has some spring preload and better quality damping. But when dyno tested it still seemed rather underdamped, so given the substantial damper travel and now adjustable damping and preload, I feel 300 lbs/inch should be fine, quite a safe choice in fact. We will see!

TT -Thanks for your useful and timely comments.

 

[Bill Thomas]

Thanks Rob, This is all new to me, Like I said it was good for my back, I will set it like Eddy sets his spring for 2 up and up the damper, Cheers Bill.

 

[hadronuk]

Thanks Rob, This is all new to me, Like I said it was good for my back, I will set it like Eddy sets his spring for 2 up and up the damper, Cheers Bill.

Just a thought. I assume your seat is fully sprung? Have you checked the mudguard is not hitting the seat? I got caught out by that a while back after making a number of changes and not checking. It's quite a jolt to the spine.

 

[Bill Thomas]

Yes, Fully sprung, I did a photo " does anyone recognise this bike", It only just touched the rebound, Didn't feel anything, The whole bike felt strange, Not been out on it for a long time, Now a "C", Was a "D", Only a few tools with me, And the Mirrors were rubbish, This bike does speed more easy than my L/ning !, So I was a bit nervous, Police !. I thought the pot holes were bigger down south !, Cheers Bill.