Swinging arm clamps

I did this mod last summer, I bought two x double split shaft collars from Bearingboys.co.uk and drilled M6 holes though them on the pillar drill, all done for about 15 quid, only thing is they're steel/zinc plated they could have back ordered stainless but I was impatient to get it done, just keep em smeared with grease to stop them corroding, but all the hard works done and swapping them later for stainless if need be wouldn't take long, it worked a treat, hope this helps.

You could use a MK3 cradle which has two pinch bolts.

You can't use a Mk 3 cradle as it does not have the slots to allow for moving the gearbox for primary chain tension adjustment. Also the three engine to cradle studs are a different size ie 3 X 3/8 rather than 2 x 3/8 and 1x 5/16"

The Mk three cradle has "bicycle pedal crank" cotter pins and is a better engineering solution than the screws into the side of the pin, I've done that to my 71 Fastback but it requires a bit of engineering and some minor welding. neat though.

Have a look at this months issue of Real Classic. A Canadian readerwrote a whole article concerning his superchargedCommando, and shows the swinging arm clamps with pictures that you have spoken about. His suggestions may or could be of some help to you.

Norman White converted my 750 cradle to the Mk3 system. It has the advantage of being visually unobtrusive and uses all standard Commando parts when replacement is needed. With the two cotters per the Mk3, the spindle is positively located and cannot turn or move laterally.

I have just put my swinging arm/cradle back together and after reading this thread bought split shaft collars from "Bearingboys" as mentioned above. I machined the centre of the collars to fit the cradle exactly. My new spindle was a good slide in fit. When clamped in place and tightened the swinging arm spindle is then held tight and you can't move it. I have decided not to drill and tap the collars to fit a 'pusher' screw (as in the Heinz Kegler method) because it holds my spindle tight without them. Thought others may be interested. Picture attached.

Regards, Alan

Hi,

I am a bit of a newbie to the world of modifications so, please bear with me.

Am I correct in stating that the Mk3 had two bolts welded to the casing through which the spindle passes and that bolts are passed through these achieving much the same outcome as the clamps to which reference is being made in this thread?

My question is what exactly is being achieved here? Is it to stop the spindle flexing, rotating or what?

Also, if my assumption is correct about the MK3, can anyone provide me with the details so that I can carryout the mod on my MK1. I am in the process of stripping it down and it would be a simple matter to weld some bolts in place, if I knew the correct size and positioning, before repainting.

Sorry if my question about how the improvement is achieved, but I like to know why I am doing things.

Thanks,

Keith

The problem with the cradle is that the bore for the spindle becomes enlarged at each end allowing the spindle to move about. The bearing collars are an easy fix. The Mk3 cradle has two small tubes incorporated in the spindle tube. These are perpendicular to the spindle tube and the bore of these tubes goes through the the edge of the spindle tube bore. With two small flats on the spindle, cycle cotter pins use the taper on them to jam the spindle in place, just like the crank on your old brit bicycle (before cotter less cranks) A good engineering solution but the bearing collars are the easy fix and probably as good as you need. Also they could be fitted with the cradle in place.

Previously david_evans wrote:

The problem with the cradle is that the bore for the spindle becomes enlarged at each end allowing the spindle to move about. The bearing collars are an easy fix. The Mk3 cradle has two small tubes incorporated in the spindle tube. These are perpendicular to the spindle tube and the bore of these tubes goes through the the edge of the spindle tube bore. With two small flats on the spindle, cycle cotter pins use the taper on them to jam the spindle in place, just like the crank on your old brit bicycle (before cotter less cranks) A good engineering solution but the bearing collars are the easy fix and probably as good as you need. Also they could be fitted with the cradle in place.

Hi David,

Although I could weld some bolts in place I think the clamp idea seems quite appealing.

Can anyone tell me what size internal diameter clamp should I use (its not easy to measure with the bike on the stand).

I have looked at bearing boys web site and they seem reasonably priced; I'll have a go.

BR,

Keith

Keith

I fitted these to my '72 Roadster and they helped a lot.

Looking at my notes I got two 1+1/8" ID shaft clamps from Tasman Industries. I used 14-28 tap for the locking bolts. The bolts were 3/4" long and fitted fine with a lock nut and plain washer.

Hope this helps

Andy

Previously keith_owen wrote:

Hi David,

Although I could weld some bolts in place I think the clamp idea seems quite appealing.

Can anyone tell me what size internal diameter clamp should I use (its not easy to measure with the bike on the stand).

I have looked at bearing boys web site and they seem reasonably priced; I'll have a go.

BR,

Keith

I bought from "Bearingboys" 2 of CADB28Z - 28mm Shaft Collar (Double Split) @ £6.84 each plus VAT & postage. Then bored them out to the exact size allowing 1.5 mm gaps in the splits. Can't remember the exact size required but it wasn't much larger than 28mm (I didn't remove much material). Regards, Alan

Previously Alan Throssell wrote:

Previously keith_owen wrote:

Hi David,

Although I could weld some bolts in place I think the clamp idea seems quite appealing.

Can anyone tell me what size internal diameter clamp should I use (its not easy to measure with the bike on the stand).

I have looked at bearing boys web site and they seem reasonably priced; I'll have a go.

BR,

Keith

I bought from "Bearingboys" 2 of CADB28Z - 28mm Shaft Collar (Double Split) @ £6.84 each plus VAT & postage. Then bored them out to the exact size allowing 1.5 mm gaps in the splits. Can't remember the exact size required but it wasn't much larger than 28mm (I didn't remove much material). Regards, Alan

Alan, I have just bought the same collars as you have. First surprise is that they have an internal bore of 26.5mm, even though clearly stamped 28mm. My spindle tube actually measures 28.7mm o/d, so it looks like I need to bore 2.2mm from the internal diameter. Does that ring any bells? Dave

Previously Dave Broadbent wrote:

Previously Alan Throssell wrote:

Previously keith_owen wrote:

Hi David,

Although I could weld some bolts in place I think the clamp idea seems quite appealing.

Can anyone tell me what size internal diameter clamp should I use (its not easy to measure with the bike on the stand).

I have looked at bearing boys web site and they seem reasonably priced; I'll have a go.

BR,

Keith

I bought from "Bearingboys" 2 of CADB28Z - 28mm Shaft Collar (Double Split) @ £6.84 each plus VAT & postage. Then bored them out to the exact size allowing 1.5 mm gaps in the splits. Can't remember the exact size required but it wasn't much larger than 28mm (I didn't remove much material). Regards, Alan

Alan, I have just bought the same collars as you have. First surprise is that they have an internal bore of 26.5mm, even though clearly stamped 28mm. My spindle tube actually measures 28.7mm o/d, so it looks like I need to bore 2.2mm from the internal diameter. Does that ring any bells? Dave

Alan, one further thought; did you shim the ends of the collars apart by 1.5mm before machining or did you mill that much metal off the ends once you had the bore correct?

Previously Dave Broadbent wrote:

Alan, I have just bought the same collars as you have. First surprise is that they have an internal bore of 26.5mm, even though clearly stamped 28mm. My spindle tube actually measures 28.7mm o/d, so it looks like I need to bore 2.2mm from the internal diameter. Does that ring any bells? Dave

Alan, one further thought; did you shim the ends of the collars apart by 1.5mm before machining or did you mill that much metal off the ends once you had the bore correct?

Hi Dave, I did shim the collars apart before machining, the collars must not clamp together, as there must be a gap in order to clamp the cradle tube tightly. I used a washer between them (maybe about 0.8mm thick) while machining. Machining off 0.35mm would enlarge the internal bore of 28mm collars to 28.7, sound about what I did. I did not remove material from the collar ends.

I did try to answer your 'private message' but your email address bounced back?

Regards, Alan