Bicycle Mechanics - Help identifying freewheel and removal tool needed.
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Hi, I'm trying to bring my wife's old bike back to life. It's an argentinian made mixed frame, with sachs-huret derailleurs and a three speed freewheel.
I'm stumped at the freewheel, as I need to remove it in order to overhaul the rear hub. I'm no bike mechanic, and I have never seen one of those. Can you help identify it, and which removal tool should I use?
Googling the text ('Unity gears') only brings me to ebay auctions.
That's an old rare bird. The tool for it hasn't been available in the US for years, bit possibly a modern BMX tool might fit. You'll have to visit a fairly old and complete LBS with the wheel in hand to see if they have one to fit by trial and error.
BTW- if the freewheel is OK, you don't necessarily have to remove it to service the hub. Disassemble the axle from the left side and slid it out. You'll have to reach in past the freewheel to clean the right bearing, but that shouldn't be hard since the opening is plenty big. Then make sure the right cone and locknut are tight on the axle and reassemble finishing and adjusting on the left side.
I can't see, but are there any splines near the axle? That two hole appears to be the lockring of the ratchet mechanism, and that two grooves appear to be from the freewheel body to hold it while removing the cogs one by one. But remove the axle and look/touch the inside of the axle hole, is it splined?
I have a russian hub with cogs, that are not removable (the cogs one by one can be unthreaded like this freewheel also, and any other, also i can remove the whole cassete by unmounting the oneway ratchet mechanism, so I'd have to demount to the pawls/those 100 little balls/ springs etc.) The fixed part of the pawl holders is cast with the hub so not removable and not interchangeable with anything - this my case, but can be in your case too, if it does not have splines inside it, and cannot see something else beside the two-hole cap (that holds the oneway ratchet mechanism), then it may be cast from the same piece.
If this is the case, you might remove the two-hole cap, and check the ratchet mechanism (pawls, fractured balls, dent raceways, pitted raceways, detensioned or broken springs, etc) to see if it worth saving the hub
If it's all in good condition, you might check the cogs if they're good. The cogs can be removed one by one, and replaced from another freewheel. But that ratchet mechanism will be stuck forever (it's cast with the hub)
But i hope it's removable and not one-piece because it's an ugly thing to change the hub (despoke-respoke-trueing, different spoke if the flanges of the hubs are not the same. etc)
05-17-10, 02:18 AM
It requires a two prong removal tool that I have never seen and is very similar to lower end BMX freewheels... better quality freewheels use a 4 prong tool that is readily available.
Have had good success using a flat bladed punch and a hammer... prior to doing this you want to shoot some pb blaster in behind the freewheel so it penetrates the freewheel threads and if you go this route you really want to keep the punch as parallel as possible to the freewheel and strike it quite sharply as tapping it gently just doesn't do it.
This may have been the old fashioned tool people used to remove these.
I hadn't considered the idea of removing the axle - at least I'll be able to clean and smother the bearings/cup in new grease.
It was very grimy, and I cleaned a bit further after the photo - there are no splines near the axle :(. The freewheel does not make a ratcheting sound when turned backwards, and it sometimes skips when driven forward, so I'll drown it in mineral spirits, and if that fails, try my luck with the two-hole cap and look inside. Cogs look good.
And if all else fails, there's the hammer and punch idea.
The freewheel does not make a ratcheting sound when turned backwards, and it sometimes skips when driven forward, so I'll drown it in mineral spirits, and if that fails, try my luck with the two-hole cap and look inside. Cogs look good.
And if all else fails, there's the hammer and punch idea.
If flushing doesn't work, and you opt for loosening the freewheel bearing cover (or cone) just loosen it a few turns, to expose a crack and spray solvent in there, then after it's dried, drip some oil in. Do not remove the cone, and disassemble the freewheel because it'll be extremely difficult to rebuild while it's still on the hub.
05-17-10, 09:54 AM
I was just trying to google for Unity--not much, as the OP found. But one of the links is to a Czech site, so maybe Unity is/was Czech, or Eastern European? If so, it might come apart in some way that's different from what we'd normally expect, as Asi suggested.
There's nothing rare or special about this freewheel except it's age. These types of freewheels were very common in their day, and were later replaced with 4s and 5s freewheels that stepped down smaller than the hub thread, and overhung the axle making smaller sprockets possible.
Like classic freewheels it unscrews from the left by means a of a freewheel remover that fits the inner body, and is built using a left hand threaded bearing cone jammed tight to a shoulder and loosened with a punch or 2-pin spanner. It's bearing play is adjusted with thin shims under the cone, which are removed one at a time as the parts wear.
These can be disassembled and rebuilt with little effort off the hub, but are almost impossible to work on with the wheel attached. If the OP wants to service it he should slightly loosen the cone, then stand the wheel in a vise with the freewheel level on top, remove the cone very carefully to expose the bearings, but making absolutely certain not to lift the outer body, lest the back bearings (1/8" or smaller) start dropping out.
BTW- with the axle out, you can improvise a piece of steel to span the two notches and remove the freewheel. In similar situations I've made removers from large bolts, filing off the corners except for two tabs to fit the F/W then with the bolt held in a vise removed the freewheel by turning the wheel.
I may also have the proper remover in my collection (to lend, not sell). If the OP will email me the ID and diameter across the notches, plus the width of the notches, I'll check and confirm, then we can work out details.
well, if you remove the cone-cap that with two holes (that is loosen in clockwise direction like the arrow says) you will probably find:
2springs for each pawl
around 100 3.175mm balls on two raceways
1-2-3 shims that can be removed in order to tighten the bearing as it wears out.
So do this over a BUCKET or a large tray to collect all of these.
Put the wheel horizontal and slowly lift the cone/cap, there you can see the balls and a part of the ratcheting mechanism.
Then put the wheel over the bucket, and slowly lift the cogs. Some balls will fall from the raceway, some will stick to the raceway of the cogs part (and the balls will fall at a slight movement, eventual into the bucket)
Study a bit how the pawls and springs are attached and remove them (first the springs then the pawls, usually on older freewheels it has individual springs like a paperclip, or like a floppy disk spring (that that holds the lid closed), or even a block of rubber to act as a spring (rarely). Anyway, remember how it was attached.
Remove all the balls and pawls and clean with a rag/gasoline/diesel/alcohol/or whatever to see the actual state of wear.
Inspect the raceway, the fixture of the pawls (if a ball was fractured it can easily get in the pawl assembly and make havoc in it like broken pawls, broken springs, and even broken fixture of the pawl it has a slot-groove-hole thing to fit in that can be cracked.
Also at this moment you can see if it's a removable freewheel (as a whole with the one way mechanism), or if it's from the same body of the hub. As I said I actually have two hubs, both of them with 4 gears from 71-73 around there (russian made), so it's not uncommon to have a non-removable freewheel, but if you can, post some pictures when you dismantle it.
Or better yet try post a picture from behind, a picture from the other side, to see the joining part between the largest cog and the fixed part of the hub.
05-17-10, 12:36 PM
What you need is on this page.
Thanks all for your suggestions and tinker ideas, especially FB for your kind offer - the shipping would be expensive, tough :)
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