22 Mar 2010

Higgins axle removal

Having shown the components of my Longstaff conversion axle, in another chapter, it seemed only fair to dismantle the Higgins. I still have no HP (clincher) rear wheels and no desire to buy another tubular tyre right now. So the Higgins is resting. I haven't checked the bearings since obtaining the Higgins so I didn't really need much of an excuse to get cracking on this drizzly, grey, Friday afternoon.

The Longstaff is still going well with an average of around 20 miles a day all week despite the endless gales and showers. A head wind is rather like climbing a steep hill. I found myself really struggling to make headway in some places. Particularly where the farmers had ripped out the hedges to their prairie-sized fields. Given a little more shelter I could increase my speed again and add more miles.

Until I get back to the Higgins I can't say whether there is really very much difference in performance between the two trikes. It is certainly much less than I remember from my first impressions of the Higgins. I may simply have been so weak, back in August '09, that the slightest difference was exaggerated and far more noticeable. Now I am so much fitter and stronger I can more easily overcome their differences with much less conscious effort. There is at least a ten pound difference in weight. (in favour of the Higgins "Ultralight")

It is certainly not something I'm going to agonise over. As do some bike riders over minuscule differences in weight. Not to mention differences in wind resistance of competing components, wheels and frames. Most of it is complete and utter nonsense unless one is competing for a world record or a serious mountain stage. Most bike components are mere fashion accessories. Nothing more. If I can hardly tell the difference between literally ten pounds in weight and tubulars versus HPs then why worry about grammes and square millimetres of frontal area?

I've seen so many Tour de France riders with their jerseys flapping like useless parachutes. That all credibility is lost regarding the drag of different components on bikes.


A friend in the US has kindly pointed out that I have not illustrated the original Higgins sprocket carrier. This is true. I had only shown the Trykit freehub-cassette adaptor in the component images further down the page. The following images are quick snaps taken with flash at -6C on the bike shed floor. I shall take some better images in daylight when it is warmer.

The back of the Higgins sprocket carrier with flats for fitting in a vice for safe sprocket removal. The tubular fixing nut is on the right.

Another view of the Higgins carrier, tubular fixing nut and hex axle taper and its screw thread for the tubular nut. The sprocket block is reversed to normal orientation.

I still don't have the proprietry tool for removal of this particular sprocket block so it has had to remain in place on the carrier for these images. No doubt some sprocket carriers have opposed threads for fixed wheel sprockets. Others will have one long thread for screw-on sprocket blocks. The normal thread is the same on both types. So a sprocket block will fit both a gear type and a fixed wheel carrier.

A fixed wheel sprocket will screw onto both types. Though it is a very unsafe combination to put a normal bottom bracket lock ring outside of a fixed sprocket. There is a great danger that both sprocket and ring will unscrew when you most need the braking power of a fixed wheel by back pedalling.

After loosening the tubular nut the sprocket carrier can usually be removed by levering behind it. Against the inner bearing cup with large, opposed screwdrivers. Mind the paintwork! See next note:

NB. The tubular fixing nut should be unscrewed a few turns but left in place. Allow enough freedom for the carrier to come loose on its axle taper. Removing the nut completely will usually mean the heavy carrier and sprocket will drop down like a stone. Straight onto the axle reinforcing loops. With inevitable damage to the paintwork. Covering the sprocket block completely with a rag will allow safe removal from the confined space between the axle casing tubes. The larger the sprockets the more difficult it is to extract safely.

As promised, here are some better (daylight) images showing both a Longstaff and a Higgins sprocket carrier side by side for comparison.

Outer or front side. The Longstaff is for fixed wheel and shows typical opposite hand locking thread and ring. I never used either carrier so there was never any need to clean them up.

Back sides which face the inner bearing. Note the much larger Longstaff with part, plain bore to ensure concentricity and help it to run true. This was not the case with the Higgins which gyrated quite alarmingly.

 Oblique view showing flats for holding the carrier in the vice for sprocket removal.

Higgins axle, dismantled views:

Dismantled Higgins rear axle components. Clicking on the image will enlarge it for a closer look. I took the picture after removing all the hardened grease with the help of some car engine cleaner. I had no paraffin or lamp oil handy.

The longer axle is the left side, drive axle. (Shown here reversed to normal) There are four bearing cones which substitute for the bearing radii of solid bottom bracket axles. These cones save the entire axle shafts from having to be scrapped when the cones become worn. (and is a very good idea!)  Chris Hewitt (Cycles) in Harpendon, Herts (UK) can supply new cones (and other essentials) at quite reasonable cost.


All four of my cones simply slid off the axles as I dismantled them. The amount of wear visible on the cones is hardly enough to worry about. (unduly) They make no noise (at all at the moment) when lubricated and well adjusted.

The longer outer cones fit the conical, inner depressions in the road wheel hubs. Thereby providing a useful increase in cross sectional area and much greater resistance to bending at this highly stressed axle area. Note how these cones are slit to allow them to press tightly on the axles when the wheel nuts are tightened. Rather like tapered collects on a lathe. Or the olives in plumbing compression fittings. A clever idea which avoids making the cones a tight press fit. Cone replacement becomes very easy even for an inexperienced tricycle mechanic.

The shorter, plain cones fit on the inner ends of both axles and have no slits. Two matching flats machined on the axles and on all four cones stop them from rotating on the axles of their own free will. Rotation might otherwise cause wear to the axle itself and must be avoided.

Three of the bearing cups on my Higgins back axle are standard, adjustable, bottom bracket fittings. Only the bearing cup behind the sprocket block is a left hand thread, fixed cup. Exactly as found behind the chainset on most normal (older) bikes. This LH thread, fixed bearing cup was not a standard feature on all Higgins trikes. (according to the experts) An adjustable normal (RH) thread cup was more often used here.

If a bottom bracket cup does not screw in effortlessly, with finger pressure alone, then do not force it!

On the left of the image above can be seen the TRYKIT freehub adaptor. The rear of the sprocket block shows the matching "star" shape of the freehub where the adaptor fits. A short taper is provided on the drive axle as a seating for the adaptor itself. The long, tubular, TRYKIT fixing nut lies beside the adaptor.

Dismantling the Higgins back axle begins on the drive side: Remove the wheel nut, spring washer, road wheel, outer cup lock ring and outboard bearing cup. Having rescued the loose ball bearings they can be placed safely aside in a container with some grease solvent.

The wheel can then be replaced and used as a lever to rotate against a spanner holding the tubular nut of the freehub adaptor. Or use an 11mm ring spanner on the hexagon on the end of the axle. Having been freed of the restraining effect of the outer bearing cup, the axle will slowly back out as the tubular nut is unscrewed. If  you try to unscrew the tubular nut with the outer drive side bearing in place the nut will butt hard against the inner cup of the idler side! So ensure you have remove the outer cup and ball bearings before attacking the long nut. Store the loose balls safely or have new replacements handy. It isn't worth using old balls due to the effort involved in replacing the rear axle components on a trike.

I used opposing screwdrivers as levers between the freehub adaptor and the (drive side) fixed bearing cup to free the adaptor from its axle taper quite easily. Gentle taps to each screwdriver handle in turn with a rubber hammer helped. Try not to damage the frameset paintwork.

The driven axle must be well withdrawn or removed before the sprocket block (cassette) on its freehub and the tubular nut will simply drop down off the axle. Some care is required at this point not to damage the paint of the frame reinforcing tubes when dealing with a large diameter, wide ratio sprocket block. (cassette) Wrapping the cassette or sprocket block in a rag before careful, downward removal will help to protect the paintwork. 

The inner bearing cup (on the drive side) can now be unscrewed and the ball bearings carefully retrieved and stored. The inner bearing cone may need to be poked out of the axle housing with a screwdriver. As did mine. The axle cones act as retainers for the ball bearings to some degree but the balls will just fall out of the cups once these components are separated too far. So have a clean tray handy underneath as you work.

The idler side, right axle is very simple to dismantle: Remove the wheel nut, spring washer, road wheel, cup locking ring, then outboard bearing cup and ball bearings. Then slide out the axle and undo the inner bearing cup locking ring, unscrew the inner bearing cup itself and then retrieve the balls.

Note: Some Higgins axles may have proper track nuts instead of plain nuts and split, spring locking washers.

Having cleaned up all the components and hastily arranged them for a digital 'snap' I weighed them all together in a plastic bag. Everything you see in the image above weighed exactly 2.5lbs without the sprocket block and its enclosed freehub.  These last two items would be present on any similar quality bike. So there is really no point in including them in the extra weight of a Higgins trike over a similar 531 butted (two wheeler) bike. Most of the extra weight of a trike is inevitably in the trike's rear axle assembly plus one extra rear wheel.

Higgins bearing cones and matching axle flats at the changes in diameter. Note how the longer cones are slotted to grip the axle as the conical hub section is pulled tightly over the taper by the wheel fixing nut. This still leaves an area  of high stress at the shoulder between the cone and the axle. Though the cone does carry some of the loads into the larger cross section of the axle it might have been safer to have used a tapered axle at this point to carry the loads into a matching internal taper on the cone. The breakage of the more highly stressed left hand drive axle in the UK would drop the rider into the shrubbery.  On the Continent a breakage might dump the rider under a passing lorry! I have no statistics (at all) on Higgins axle breakage.

Note: The Trykit replacement axles (intended for replacement journal bearings) carries the full diameter of the axle at the journal bearing point right through to the wheel hub conical taper. As the journal bearing is larger in internal diameter this makes the Trykit journal bearing axle much stronger than the original Higgins. There are also no local stress points either where the flats and shoulders are formed for the loose cones on the Higgins axle. The quality of the modern steel used by Trykit is much higher too. The Trykit journal bearings fit into specially machined bottom bracket cups. This means that a Trykit modified to take replacement (journal bearing) axles can be returned to original cup and cone bearings simply by reinstating the original components.

I think it  is obvious from the image how much slimmer the Higgins axles are compared with the Longstaff. The Higgins main axle sections are 9/16" (14mm) and the wheel sections reduced to 1/2" (12mm) at the cones.  I presume the steel is of high quality and carefully selected from straight bar. The Higgins uses bearing cups and cones instead of the Longstaff journal bearings of course. Though I doubt there is very much difference in weight between the bearing types themselves. Now I wish I had measured the diameters of the Longstaff axles for comparison. I'll update this detail when I get a chance to measure the Longstaff axle with a vernier calliper.

[edit] The Longstaff stub axles are 15mm. A full 3mm or 1/8" larger than the Higgins. There seems to be two types of Longstaff axles. One is waisted between the two raised bearing stop rings as seen in the TRYKIT gallery. The other remains at full diameter over the full length between the bearings. (like my own) I imagine there is some weight saving with the waisted version unless mine are tubular and I haven't yet noticed. Judging from the images I posted in the Longstaff axle chapter I imagine my own Longstaff axles are 3/4" or 18mm except where they are reduced to 15mm at each end.

I have read recently (online) about Higgins axles breaking. Hopefully a very rare event. There does seem to be a tress point where the axle material is reduced to fit the cones and hubs.  Despite the Higgins cone spreading the loads into the hub there is no radius where the two different axle diameters meet. A reasonable radius at changes of diameter is a known engineering device to reduce the risk of failure at shoulders on heavily loaded shafts. The flats may also introduce further weakness at a critical point of the axle. On the other hand they may help to spread loads since they are of intermediate cross section between the two diameters.
Geoff Booker at Trykit will provide a whole variety of new trike axles to order. Including 9oz lighter, tubular axles and oversized axles to convert the Higgins to journal bearings. He also offers light alloy cups bored out to take journal bearings for the truly weight conscious. One can even have new Higgins trike axles made to take the larger bore Longstaff or Trykit hubs.

The Higgins frameset has only about 18mm (3/4") internal diameter to its axle casings. Which limits what might be possible with very large bore, thin wall, tubular axles as a potential weight saving measure. Something for a dedicated tricycle builder to ponder over perhaps? There might be a good couple of pounds to lose this way if suitable hubs could be bored oversize too?  The axles are where most of the trike's extra weight (compared with a bike) is concentrated. I believe Trykit trike and trike conversion hubs are 15mm bore. 

I'd better not pinch any more of Geoff's excellent website images or he might get cross.  So here is his trike component gallery link instead: His replacement axles are in the centre at 13, 14 & 15: 


That Trykit two wheel drive conversion is looking more attractive every time I stare at the images. It would stop my front wheel skipping to the right on steep hills and similar right side of the road left hand drive problems. I would also have the longevity and quiet, smooth running of journal bearings. 

Reassembly note: Make absolutely sure that the cones are resting on the locating flats of their axles as you put everything back together again. If you tighten the cups with the cones not seated properly on the flats they will eventually turn enough to seat themselves properly. Then suddenly take up the difference in length between the cones and become very sloppy indeed! You do not want this happening out on the road! Rotate the outer cones with a pair of thin nosed pliers as you assemble the axles and they will seat properly. The inner cones are a matter of trial and error because they cannot be easily reached. Though jamming with a small screwdriver might hold the cones still enough while you rotate the axles slowly by hand.

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This chapter has been updated. 1/7/2010 and 29/8/2010 and 21.2.2011.