Brant's Virago trike

[Brant]

Cont.

Wheels and gearing.

Checked out gearing and figured 195/65 x 15 tyres with the ‘B’ axle ratio would give original Virago gearing/ speeds +6% so run with that. 

Not happy to slap wheels with 100mm PCD on hubs with 4” PCD studs, tighten up nuts and blast off (concentricity and bending/ overstressed stud issues).  I know it works for most people but ........................ 

Anyway, I machined a spigot on each axle hub and wheel adaptors were made with matching recess, the adaptors having O.D. to suit the wheel bore.  The adaptors are fixed to the hub with the half shaft nuts (replacing the nut plain washers).

I chose wheels for 12mm studs and tapered seats but retained 3/8” studs in the hubs (just longer to suit wheel extra thickness) then assembled using, in order, 12mm cone washers, 3/8” plain washers, Schnorre washers and finally 3/8” stud nuts fitted in reverse so the nut flat face abuts the Schnorre washer.  This arrangement gives sufficient clearance to allow the cone washers to be tightened without studs touching hole sides thus no stud bending and wheel concentricity is maintained

[steve brock]

I thought that until I did it, the nova discs have bigger holes than the studs so the pcd works out !! My 2 cents

[Brant]

I thought that until I did it, the nova discs have bigger holes than the studs so the pcd works out !! My 2 cents

Thanks Steve. 

I'm using drum brakes and not familiar with disc setup.  Using studs on 4" PCD and wheels having 100mm PCD, do your wheels pick up for concentricity on disc spigot and if so how then is the disc located concentric on the hub in order the wheel runs true. 

Be patient with me this is my first time trike so I know not much.  Knowing a bit more about the disc arrangement might persuade me go that route if I do another.

[morrag]

You are both correct, I have used both the original drum and the "MM" Nova/Golf disc set up, and with the Nova discs there is sufficient free play in the original holes, so provided the hub register is machined to suit the Nova disc, no probs.However, when using anything other than 4" PCD wheels, I re-dril them to suit the 4" PCD, and as I invariably use ex-Ford alloys, they are plentifully and cheap! there is sufficient "meat" to do so.Morrag

[steve brock]

Erm first of all your scaring me wiv big words urm I had to turn or knock of the corners of the hub so it fits the disc also turned the face of the hub step, to match the discs big hole. I knocked out the studs and replaced with bigger studs (or the disc rotates on them with a clonk..) mk3 golf gti calipers on mine only couple of minuetes on the lathe..

[Brant]

Erm first of all your scaring me wiv big words urm I had to turn or knock of the corners of the hub so it fits the disc also turned the face of the hub step, to match the discs big hole. I knocked out the studs and replaced with bigger studs (or the disc rotates on them with a clonk..) mk3 golf gti calipers on mine only couple of minuetes on the lathe..

Thanks Steve.  Have you read Morrag's note?  If I understand correctly, for his disc arrangement, he ensures wheels run true by machining a hub concentric location to match with the disc, in turn the disc accurately locates the wheel.  To then avoid bending the studs (vital in my view) he machines the wheel stud holes from 100mm to 4".  This achieves same end result as my arrangement for drum brakes.

In your arrangment, again if I understand correctly, provided the corners of the hub are turned concentric and the disc location is true then your wheels should run true also.  But, ......  (a) unless the wheel stud holes and wheel studs are on the same PCD (Morrag) or, (b) there is some misallignment compensation (my oversize cone washers) or, (c) the stud holes are oversize and plain nuts not tapered are used (dodgy?) then the studs will be put under a bending load.

Sorry but seem to have rambled a bit.  Does any of that make sense?

[Brant]

Any pics from the rear showing the springs brant ?

Will take piccies from directly above and behind to better show the angles. Post when can.

Hi Zak.
Piccies as promised to indicate shocker angles.

Trikerpete and Cabman both wise to mention the safety aspect, I appreciate their concern and comments are much appreciated.  Nonetheless I gave it quite some thought and am happy to run it.   I wouldn't advocate anyone to just eyeball it and if not confident to do the geometry then best leave it alone (though using spherical joints rather than rubber gives a lot more latitude).

If only to clarify my own thinking I'm open to discussion on the detail.

[steve brock]

Hi brant, good to bounce the ideas off----all I know is that it seems to work ok, yes I agree there could be ever so slight if none pressure applied to the studs when tightening the wheel nuts fully down, I just know that it feels ok when I  fit the wheels on and it all runs true-- my studs are quite long for the wolfrace wheels and I tapped the hubs to m12 x 1.5 pitch so perhaps there is some play to be used as opposed to press in studs (i have nuts welded on the back of the studs too) works well n looks 'natty' or in your words concentrically running Non disproportionately well! ..

[Cabman77]

Pete and I were pointing out that the bottom mounting on the shock itself will be having adverse stress put on it in the wrong direction. Bear in mind the bottom mounting on any shock absorber is only spot welded onto the base of the shock, which is fine if only stressed in a straight line through the shock (in compression). The way you have yours mounted is fine for an IRS set up but a bit risky on a solid axle fitting because the stresses through the bottom mounting will be at an angle to the shock absorber with the inherent risk of the spot weld breaking (side stress). I have seen this happen on an old XS650 and that was because of knackered swingarm bushes, with only a small amount of sideplay at the bottom mount. You may be right though just thought I`d let you know what we were getting at.

[Brant]

Hi brant, good to bounce the ideas off----all I know is that it seems to work ok, yes I agree there could be ever so slight if none pressure applied to the studs when tightening the wheel nuts fully down, I just know that it feels ok when I  fit the wheels on and it all runs true-- my studs are quite long for the wolfrace wheels and I tapped the hubs to m12 x 1.5 pitch so perhaps there is some play to be used as opposed to press in studs (i have nuts welded on the back of the studs too) works well n looks 'natty' or in your words concentrically running Non disproportionately well! ..

Hi Steve.
We've each got our own take on things and so long as it works for us then fine.  Be a strange world (and boring) if we all did things the same way.  As you say it's "good to bounce".

[steve brock]

Are you running at full tyre pressure? What's your take on that?

[Brant]

Are you running at full tyre pressure? What's your take on that?

Hi Steve.
I've very limited experience of trikes so anything I say must be suspect.  There are knowledgable guys hereabouts who will give proper advice.
For my bike trike I listened to others and tried front tyre at standard bike pressure and rears at 15psi.  Works fine for me but I suppose it depends on such things as overall weight, weight distribution, tyre size, speed, etc.  Try various pressures and choose that which suits you best I suppose?

[Brant]

Pete and I were pointing out that the bottom mounting on the shock itself will be having adverse stress put on it in the wrong direction. Bear in mind the bottom mounting on any shock absorber is only spot welded onto the base of the shock, which is fine if only stressed in a straight line through the shock (in compression). The way you have yours mounted is fine for an IRS set up but a bit risky on a solid axle fitting because the stresses through the bottom mounting will be at an angle to the shock absorber with the inherent risk of the spot weld breaking (side stress). I have seen this happen on an old XS650 and that was because of knackered swingarm bushes, with only a small amount of sideplay at the bottom mount. You may be right though just thought I`d let you know what we were getting at.

Hi Cabman.
This is a safety issue and I very much appreciate comments from you, Pete and anyone else.  So thanks 

I know entirely where you’re coming from.  Shocker rubber bushes are intended mostly to take radial movement and although they will absorb some axial movement (though "sideplay" or whatever) too much could easily overcompress the rubber and strain the bush eye weld.   

Knowing the problem and nonetheless, for various reasons, I got fixed on the idea of a shocker setup acting close to the wheels as possible but without the complication of IRS.  Eventually I convinced myself there should be a combination of suspension geometry and shocker mount angles that would do the job within limits of the rubber shock bushes.  So that’s what I’ve attempted.

In my arrangement both top and bottom shocker bushes lay exactly on the arc of the swingarm (to minimise angular deflection of bush axis to eachother) with the top bush inboard and forward of the bottom. Axis of top and bottom bushes are aligned and set at an angle corresponding to give radial deflection of the bushes when the shocker moves in and out.  Bush axis are not aligned as might be for IRS nor as might be for simple swingarm but (a) tilted and (b) at an angle between the two.

I’m aware this is beginning to sound like a load of old cobblers (and it may well be) so I’ll stop.

Bottom line is, does it work and is it safe?  Well it’s a stable and comfortable ride and it ain’t bust yet.  But that’s not to say it won’t break.  To prove my thinking and be sure of safety I think the deflection at bush axis needs to be clocked and I’ve an idea for a test rig.  Can’t promise to do it any day soon but when results are known I’ll post them.  If it turns out a load of XXXXXX I’ll simply replace the rubber bushes with wide angle spherical joints.

Meanwhile I’d be pleased to hear more comments (you might save my neck).

[zakboy]

personally Brant i do prefer my shocks parallel to each other so the top and bottom mounting point are on the same plane allowing the shocks to compress fully ,i think as that angle of the shocks and mounting points changes at one end away from the parallel of the center line of the bike then i feel the less they may compress as the angle gets wider till the angle is so that they are more likely to flex and twist.and the stress is pushing outwards on the mounting point rather than down, but this is only my own personal view

[morrag]

Hang on, this is a trike with a "live" back axle, its never going to be an F1 Ferarri! The units will work fine as you have them, believe me...Morrag