I have had the same issue with Aluminium bronze guides, the trick if you end up with a slip fit instead of a press fit in the housing is to copper plate the OD in a copper sulphate solution, varnish the surface you do not need plating. Reaming the ID is best done with a flex/ball hone as HSS reamer wears out before the first cut is finished and just rubs creating heat.
Reaming the ID is best done with a flex/ball hone as HSS reamer wears out before the first cut is finished and just rubs creating heat.
If I don't attack the bottom end of the engine in the right order (determine current balance factor, disassemble crank, remove and weigh small end reducing bushing to allow for a revised determination, etc.) it will mean extra work for me. Given that, my current plan(*) for the new small end bushing is to take into account Ampco's machining recommendations to turn the OD to the required oversize for a proper press fit, bore the ID to a to-be-determined size that is smaller than the final size (keeping in mind the ID will be reduced somewhat after the press fit), press it into place, and hone it to the final diameter to give the necessary clearance for the wrist pin. All the while insuring the bore of the bushing is precisely parallel to the crankshaft. Piece of cake, eh?...
Final honing to size may prove to be the most difficult part of this (although, not yet having machined the material, I may find problems there as well). For that my plan(*) is to use an appropriate Sunnen hone that I'll adapt to fit on my mill. Yes, I know I could hand it over to a machine shop to have this done for me but what's the fun in letting someone else screw it up when I can spend more money and time screwing it up myself?
(*)“No battle plan survives contact with the enemy.” Field Marshall Helmuth von Moltke
The bar of Ampco 18 aluminum bronze was delivered today but it will be a few days before I see how it machines. Not unlike that on Britbike, advice on machining forums ranges from excellent to... well, let's say, less than excellent. And, like Britbike, it's not possible to know whose advice to pay the most attention to without having spent time following other posts. This is relevant because advice on machining aluminum bronze ranges from saying it cuts 'almost like butter' to 'similar to tool steel', with a range of advice on the cutting edges to use. I think I've sorted all that out but I'll only know once I have it in the lathe.
McMaster-Carr, a favorite supplier of mine, gave a tolerance range on the diameter, and the rod I received came in slightly over the nominal 1-1/2" at 1.55" (also 1/8" longer than the 12" I paid for). However, there's a casting skin on it so I won't know its useful OD until I machine that off. In any case the OD is more than enough than needed to produce the final ~1.19" OD for the bush.
My initial plan is to modify the cutting edges of a sacrificial 25/32" (0.781") Silver & Demming drill to the geometry best for Al bronze that I found from a credible source. That will leave ~0.031 to remove using a boring bar with carbide insert to achieve the 13/16" of the gudgeon pin. I'll leave an appropriate amount of material (~0.001"; exact value to be determined) and sneak up on the final required ID, including the necessary clearance, with a Sunnen hone. Since its thermal expansion is similar to Al I'll allow it to cool before doing the final work on the OD and the ID. Anyway, as Gen. Custer said to Maj. Reno as he rode out that morning, "That's the plan..."
The honing unit arrived two days ago but I will need to design and make an appropriate holder for it. This unit only operates over the limited range 0.806"-0.837" (nb. 13/16" = 0.812") and is made to be used with a Sunnen honing machine having the necessary mechanism for the push/pull mechanism that operates on the stone to press it against the ID with adjustable pressure.
The stone is mounted on a holder with a 20o ramp so if pushed on by a 1/4-28 cap screw, a one-sixth turn would raise the stone by 0.002". I'll need to fabricate a holder with a bolt operating on it and a strong return spring that is suitable to mount in my lathe. With the small end of the rod in place, turning the cap screw until resistance is felt, plus a little, should be what it takes. I'll practice on a scrap piece of bronze first to get a feel for how fast material is removed.
The stone is mounted on a holder with a 20o ramp so if pushed on by a 1/4-28 cap screw, a one-sixth turn would raise the stone by 0.002". I'll need to fabricate a holder with a bolt operating on it and a strong return spring that is suitable to mount in my lathe. With the small end of the rod in place, turning the cap screw until resistance is felt, plus a little, should be what it takes.
An M5.5 x 0.5 cap screw should allow finer adjustment, if you can get hold of the appropriate screw and a tap to thread the holder.
An M5.5 x 0.5 cap screw should allow finer adjustment,
Thanks for pointing that out, but I hope finer adjustment won't be necessary. The mechanism I have in mind to make will push against the stone with a spring so it will be encouraged to advance into the bushing rather than being forced to. Unless the stone removes material very rapidly, even with the same setting of the adjustment it should take several sessions of cutting and measuring to approach the desired final ID value.
Although most of the garage time the past three weeks has been spent getting my Catalina Gold Star ready for a friend(*) to ride along with me on my BB Gold Star, that seems to have been accomplished (knock wood). Assuming no significant issues are revealed in the next few days as I put ~200 miles on it prior to a break-in oil change, and after carefully checking over the BB, attention will return to the Ariel.
(*) the Irish friend who sold the Ariel to me
Despite not working on the Ariel it hasn't been off my mind. It's been some years since I last fitted new rings to a bike, and previously I just filed them to get the correct end gap, but yesterday a more serious ring filing jig arrived to use when that time comes. I also purchased a ring expander because I couldn't find mine. Of course, I found the old one after the new one arrived. At least they're of a different design so I'll have a choice.
Although I haven't done any work on Ariel, I did direct some of my attention to the less urgent matter of the speedometer. These were optional accessories at the time and my bike came without one. Before work came to a halt I had bought and installed a speedometer ring gear and 90-degree drive for the rear wheel, and the current drive and driven gears are correct for a ~1600 turns/mile speedometer giving me several easy choices of Chronometric or magnetic speedometers that I already have. However, it would be easy enough for me to machine a new driven gear to give a different ratio so I'm torn whether or not to look for a period-correct speedometer. It's not like this is a critical decision since actual navigation will be handled by a bicycle speedometer that I can accurately calibrate to the actual rolling diameter of the wheel, but I am keeping my eyes open to see what's available.
Please keep writing, this is the most interest motorbike story on the net right now.
Thanks very much for your comment. I know people read this thread because of the number of views it gets, but it's always nice to have feedback. I'd be happy to stand corrected, but this may be the most complete description of the rebuild of the oldest bike on BritBike.
Originally Posted by old mule
Bonnikson, if they didn't cost more than the bike!
A friend has a Bonniksen on his Levis and it really is the Rolex of speedometers. It was one of two optional speedometers offered for my Ariel in 1928. If the £63 the bike cost then is equivalent to a $15,000 motorcycle today, the Bonniksen at £5.00 would be a $1200 accessory.
Today's Ariel progress was the arrival of a fire extinguisher. At least two bikes have burned to the ground on previous Cannonballs, and a bike that caught fire at this year's Irish Rally was saved by the quick action of a hotel employee with an extinguisher.
A 1 kg Class ABC foam extinguisher (B is for gasoline) has a discharge time of 8-10 sec., which seems to me at least twice as long as is needed. If gasoline leaking from the tank or carburetor is still burning after 8 sec. it's probably hopeless. Anyway, whether right or wrong, after looking at such an extinguisher I decided it was too big and instead purchased a non-refillable 1 lb. extinguisher to carry on the Ariel. I'll have to figure out a way to mount it as far back on the motorcycle as possible in a way that keeps it from falling off but still allows it to be rapidly retrieved.
A 1 kg Class ABC foam extinguisher (B is for gasoline) has a discharge time of 8-10 sec., which seems to me at least twice as long as is needed. If gasoline leaking from the tank or carburetor is still burning after 8 sec. it's probably hopeless.
Mmmm ... another way of looking at it is, if the initial fire is extinguished in less than 8 seconds, there is some in reserve if the fire reignites? Depending on the size of the leak and the quantity behind it, a leak could go on for several minutes. Extinguishing the initial fire and tipping the bike over could direct the leak away from the initial heat source. But in vain if the vapour reignites from another source and nothing in reserve in the extinguisher?
On that basis, pound-for-pound, might a CO2 or dry-powder extinguisher be more useful? Albeit CO2 isn't the greatest for cooling a heat source quickly.
another way of looking at it is, if the initial fire is extinguished in less than 8 seconds, there is some in reserve if the fire reignites? ... might a CO2 or dry-powder extinguisher be more useful?
I can't argue that there certainly could be circumstances where a small extinguisher wouldn't be enough while a bigger one would save the day. In the end the choice requires a (problematic) judgment call on a (problematic) risk assessment.
The fire I observed myself a month ago was caused by fuel dripping from the carburetor being ignited either by a backfire or by a spark from the magneto below it. Either way, once the fire was out there were no more sparks or backfires to reignite it. Although it was hit with two blasts of an extinguisher of less than a second each, I'm pretty sure the fire was out after just the first blast.
A bike burned to the ground on last year's Cannonball when its exposed pushrod came free and punched a hole in the bottom of the tank while underway. I suspect in that case the leak was of such magnitude that by the time the rider managed to stop the bike only a large extinguisher deployed very quickly might have saved it.
As for the type of extinguisher, CO2 works by displacing the oxygen and is great for electronics because it doesn't leave a residue. However, It could require a lot of CO2 in an outdoor location, especially if there were even a tiny breeze. A Type B foam unit is what is recommended for gasoline fires and I can't think of any reason to question this recommendation for an extinguisher to carry on the Ariel. Fingers crossed that I won't have the "opportunity" to find out if my judgment on this is correct or not.
I have been looking at these fire extinguishers. ...
Although halon fire extinguishers are rated for gasoline as well as electrical fires you have to pay quite a bit more for one and it seems to me the advantage they have isn't really relevant for our use. Further, there's the issue of how well they might work in a breeze.
Halon extinguishers leave no residue so they are great for electronics as well as anywhere indoors (or inside a car) because powder or foam would leave a mess on furniture or in carpets. But, not adding additional residue to the outside of a motorcycle engine that's already covered with oil, grease, and road dirt doesn't seem to me to rate a big plus in the 'advantages' column.
A bigger issue is we need them to work outdoors in a breeze, not in inside an office or car. If you cover 90% of a burning pool of gasoline with foam, then pause, you can then resume and put out the remaining 10%. However, if you pause with a halon extinguisher in a breeze, or if it is windy enough and even if you don't pause, as soon as the halon is blown away any remaining flames will quickly have the gasoline back to burning at 100%.
Anyway, for what it's worth, I'm going with a foam extinguisher for the Ariel.
Returning to the Ariel, so to speak, as far as I can tell I now have my Catalina completely finished (knock wood) so as long as nothing develops during a short ride on it and the BB Gold Star this weekend I'll refocus on the Ariel. In another week it will be five months since the Ariel arrived, and there is now less than 12 months remaining before the Cannonball. So much still left to do; so (relatively) little time.
The no foam residue is the reason I like this fire extinguisher. If I have a small fire and are able to put it out without the foam residue mess it may be possible to make repairs and keep going. I have cleaned bikes that have had foam all over them. I would pay extra not to have to clean that mess up. The breeze stuff I did not think about. Going have to check on that.
The no foam residue is the reason I like this fire extinguisher. ... without the foam residue mess it may be possible to make repairs and keep going.
I think you're putting too much emphasis on the mess factor. An extinguisher small enough to carry on a bike is only going to put foam in a relatively localized area of the engine and be easily wiped away sufficiently afterwards to fix whatever needs fixing. Foam only would be all over a bike if the fire got big enough that it only could be contained with a large extinguisher, in which case the bike would be toast anyway because it wouldn't be carrying an extinguisher that large.
Originally Posted by RPM
The breeze stuff I did not think about. Going have to check on that.
A large halogen extinguisher could make sense in the evening work area where covering exposed tools and spares with even small amounts of foam from the overspray would be more of an issue. Also, even on a windy day the surrounding buildings and trucks would reduce the breeze in the work area to less than would be experienced by a burning bike on the side of the road in the Badlands of North Dakota.
This issue may be like an oil thread, i.e. there are countless opinions but no "best" answer. Although, similar to oil (i.e. any oil is way better than no oil), in the case of a fire on a bike, any (Class B) fire extinguisher is way better than no extinguisher.
Returning at last to the Ariel, I bought a cheap 4-shelf shelving unit and moved all the Ariel parts, except the exhaust system, from being neatly laid out on the floor to being neatly stacked on the shelves. A few small items had collected on one of the work benches as well, and now they too are on the shelves. As well as helping with the overall organization of the rebuild this freed up a useful amount of floor space that I can now clutter with something else.
An Irish friend, Chaterlea25, offered to look into finding PB1 bronze for me to use for the small end rather than the harder Al bronze I had planned to use. Since he knows from his own experience that PB1 works in this application and is easier to machine than Al bronze it's worth using but, although I can find the composition of PB1 on line, finding an exact match to the equivalent "American" bronze proved problematic. If he can find someone who sells 1-1/4" bars in small quantities the postal service will get rich from transporting it to me.
Making this an all-Irish post, the friend who sold me the Ariel, and who will be my teammate on the Cannonball, arrived for a visit. The pause in the Ariel's progress this past month was due to getting two Gold Stars completely -- I hoped -- ready for the two of us to ride on a 1200-mile mini-Cannonball. Results of that are described elsewhere. It only should have taken a week to get them completely seaworthy but it required nearly a month, consistent with the fact that such estimates always are off by a factor of π.