Rear sprocket/drum (2013)

This is what my proposed new cush drive setup will look like from the outside, impossible to pick from stock
although the purists who would not consider using non genuine parts wouldnt be interested.
I would think this decent cushdrive would be popular with the Triton etc guys
Of course the standard brake,hub cover would be used,

hobot said:

Being Norton there may of been a number of ways to fasten the pegs but 5 of the Combat era ones I've dealt with were all staked or crimped in place, which with heat and time and loads eventually allowed all of these 5 drum pegs to twist so needed welding in place, but need to grind out or melt down below surface as brake shoe sweet past close enough to leave witness marks, ie: cant have any bead above surface to matter. Put question to other lists so may get it ID'd.

Click to expand...

Could be early drums weren't welded. These are pictures of the drum that came from the factory on my 1971 PR. I modified it back in the '70s so I could change sprocket sizes, and to take a one piece axle, but the welds you see for the pegs are factory original. FWIW I bronze welded the adapter ring on to avoid distorting the drum too much, but still had to turn it afterwards to get it true.






Ken

45t, not sure how many would want to gear down their road going Nortons, most are going the other way and fitting larger 22,23,24 tooth gearbox sprockets, its not that easy to fit a bolt on 42t sprocket and certainly near impossible to go smaller than 42 successfully.

What is the largest front sprocket available right now? 24 seems to be the largest I have seen.

If you stuff the largest front sprocket in, and have changeable rear sprockets, it would make for quicker change overs.

You could go from the road sprinter to long distance cruiser in a matter of minutes.

One would need to do the maths to see if this idea would be feasible. Just spit balling here.

I do like the improved cush drive, looks modern and effective.

Brent you have described how Peel is set up for very wide scope of operation, Trials to parking lot stunts to landspeed. If Maddass had offered this a decade ago Peel would of jumped on it. Like the items produced by Dreer, Sir Eddie and others, how long a window of opportunity will we have before kicking self for not acting while available. How many weekends left? In lots of ways this last and next decade may be the best golden age of our Commando's...

In 1971, my first Commando, with about 500 miles on it, locked up the rear wheel on the freeway - one of the paddle pegs had backed out and jammed in brake shoes. IIRC, the pegs appeared to have brazed in but a bad job on mine. Brian Slark express shipped to me a new drum and backing plate.

Nice parts Ken.

Would sign up for a new stockish looking rear with improved cush.
If it was easier to mount and dismount the tire, that would be a bigger
plus than a demountable sproket. It is a PIA to remount when you have
newish cush bits in.

Those pegs in the Commando rear drum were initially brazed on and these are
dangerous because they can snap off and get into mischief inside the wheel.
The later ones are actually large screws installed in threaded holes in the
drum, then peened to hold them in place. On my previous drum (which wore out years ago) they had become wobbly, so I unscrewed them, cleaned the threads, and reinstalled them using JB Weld as my thread-locking compound.

Mike Taglieri
-----------------------------------------------

On 5/4/2013 10:46 PM, Toll Fast wrote:
Depends upon which bike you are talking about.
BSA used Nikasil which is a nickel silicon iron.
Casts beautifully work hardens.
Usually they were cast and then the hub was attached by either rivets bolts or
being cast into the alloy drums.

Bike Beesa
Trevor

madass140 said:

45t, not sure how many would want to gear down their road going Nortons, most are going the other way and fitting larger 22,23,24 tooth gearbox sprockets, its not that easy to fit a bolt on 42t sprocket and certainly near impossible to go smaller than 42 successfully.

Click to expand...

Agreed. I was using 1.75 and 1.78 primary drive ratios instead of the stock Commando 2.19 ratio, so the larger rear sprocket wasn't a problem. But for most Commando owners, the larger sprockets would be an undesirable feature. I eventually switched the rear wheel out for an 18" by 2.5" mag wheel with homemade cush drive, and typically ran countershaft sprockets from 18 to 21 teeth and rear sprockets from 40 to 46 teeth, depending on the track and which engine was installed (750, 750 SS, 920). Your arrangement looks perfectly suitable for a normal Commando, and I wouldn't hesitate to buy one if I had any Commandos left with rear drum brake.

Ken

hobot said:

Those pegs in the Commando rear drum were initially brazed on and these are
dangerous because they can snap off and get into mischief inside the wheel.
The later ones are actually large screws installed in threaded holes in the
drum, then peened to hold them in place. On my previous drum (which wore out years ago) they had become wobbly, so I unscrewed them, cleaned the threads, and reinstalled them using JB Weld as my thread-locking compound.

Click to expand...

Interesting point. As I recall, the pegs on the drum I posted above do show a brass color on the back side around the pegs. It's possible that what I called welding on the inside is instead bronze welding. Can't tell from the pictures, so I'd have to dig out the old drum to tell. I'll look for it today, and post an update.

Ken

Ken that was a quote form NYC Micheil Tagilari i just passed on here. All of my 15 pegs I've seen from Combat era drums began twisting at some point and some could be turned freely in a circle, but didn't notice them threaded to change their seating depth as I learned how loose they can become. I think we had a post here or there of a peg working into brake shoe to lock up at freeway speed. I did not recognize that risk till now as mine were only twist loose, not shift loose, yet tore up the tire case cushions by concentrated side forces of thinner side section of peg or their obluque 'corners' chewing cushions up. I have given up on the whimpy factory cushions as even when every thing tight and square they just turn to crumbles melt and dust on a few rides.

One factor, I've two examples of now - is when the dual row bearing looses its grease and gets loose the drum wobbles enough make cushions into chewing gum + cob web of fibers even with pegs nailed down. Took me a few seasons last year to figure out why my dry chain was going slack on every ride and cushions gone within 10 miles, discovered d/t a flat right after replacing cushions. The bad bearing cracked the too shallow weld on Trixies hub loose again so next time will drill to fill or weld on back side of peg bosses.

Brit Iron listee
On 5/6/2013 9:19 AM, hpshooter@juno.com wrote:
>
> In my 30 years in iron foundries we made many thousands of brake rotors, both vented and solid for Ford and Chrysler and brake drums from 10 inch diameter to 20 inch diameter for Cat, Mack and Bud Wheel from good old class 30 gray iron. The 20 inch drums for Bud Wheel had a pressed steel "top hat" cast in the center where the mounting bolts and wheel studs went through the drum.
>
> Some rail roads still use a limited number of cast iron brake shoes on older locos and cars, made them also.
>
>
>
> T W Hudson

Hello Forum. hope life is good for you all.

Mr Madass: been watching this and dont seem to see a specific answer to your question of what material?. therefore I will have a go and see where this ends up. if you already have this stuff please ignore this post.

First up lets not talk of cast steel being a grade. it is not. many grades can be cast. for this post steel is the selected material.

Material: K1045 the k is important as ithe steel requires further heat treatment . killed steels are especially suited for this application. some important properties are, good toughness, 40 tons approx tensile, easily machined, commercially available, less costly than alloy steel, is well proven for this application, and has enough carbon to take flame or induction hardening.

the big thing is the foundry doing the job. some small foundrys can produce absolute rubbish. inclusions, hard spots, terrible. the quality and cleanliness of the cast metal will determine the sucess or not of the project. this cannot be overstated.

having got a raw casting , several things would now be necessary.

Normalize the casting. this is necessary. then rough machine or whatever you reckon needs doing at that stage. the teeth blank part needs to be finished here,to allow tooth cutting.

cut the teeth. then flame or induction harden the teeth. the tooth hardness is 55RC at least on the tooth. myself I would temper back to about 40/45 after hardening. get a bit of toughness back. for this application special burners could be easily made to get localised heat into the tooth quickly. flame hardening would be the best way here. tempering at this stage would help also to let a bit of stess go as well.

Finish machining. sell lots of.

hope this is helpful
errors, omissions and corrections welcomed
Bradley

Yes very helpful Bradley, thanks for the rundown, much food for thought there. to simplify production a bit,
maybe a revision is needed, Cast iron unit with separate steel sprocket (somehow attached)???
with a 42t sprocket on the 7" drum there is not much room for sprocket bolts, I had considered a L.H thread (1.5mm pitch) turned on the sprocket mounting area up to a shoulder and thread the sprocket I.D.
Tightened extremely tight with Loctite applied. It certainly wouldnt get hot enough to release the Loctite and I doubt thread stripping would be an issue. I guess a sample could be produced on an existing 3 peg sprocket drum and hand it over to Hobot for testing, the only difference would be the test unit would be steel sprocket on steel drum as opposed to my above suggestion of steel sprocket on cast iron drum,

I've strained my wee mind on how to make replaceable teeth ring so interested to see how others conceive it. At some point you end up like Kenny Dreer, ain't no way to really get all you want out of a real Norton item, then start from scratch so it will still plug in to the basic Commando. The screw on method is a cleave idea.
The rear brake don't need to be very strong so a smaller dia drum would allow room for more practical fastening method. Maybe just interference fit by heating the ring and cryo freeze the drum so they lock together and drum heat would just bind all the tigher? Not much a rim remains when old teeth milled off may be enough.

there is that groove on the face of the sprocket drum for the brake plate to enter about a 1/16" or so, therefore to screw on or interference fit a sprocket for testing purposes only I would have to move the sprocket inboard about 2-3mm to get a 100% mating surface (diameter)
But I think you maybe wright Steve, an interference fit would work, I've done a lot of that in my workplace over the years, there would be no need to freeze the sprocket as enough interference would be created by
heating the sprocket alone as it is very thin walled compared to its diameter. I reckon 10-15 thou when heated.

hello All again.
just a quick reply. I dont know much about economics regarding manufacturing, but where you gain on swings, you lose on roundabouts most times.. I suppose a study would have to be made regarding such things as machining costs against castings, and trying to keep things simple.
Madass:, i also suppose it depends on the numbers you wish to produce per run. Pattern costs would be a once off, or you could even make your own. My view is that your novel feature is the better spider, and as the original sprocket lasts a long time, focus on the cush drive features.

if the original item works regarding the brake, a one piece item may be the best way of idiot proofing your design. heat treatment costs may be cheaper than machining several components, and there still may be heat treatment required. I dont think a steel in a machinable condition, would have enough surface hardness for sprocket teeth. gear cutters dont like hard materials either. knocks the hobs around too much.

Just a final observation: to make a 2 piece item still requires a casting, decent quality sprocket needing heat treating, extra machining and assembly. then you sell it and have no control over the usage. A study on costs needs to be made.

Regarding iron:: that is a different kettle of fish. however a competent foundry would be of great help. they can cast any composition you wish. dont know much about irons, but this may be another alternative deserving of a case study. I am sure there is an iron that will do the job. though surface hardness of the teeth may be an issue with wear. however there are high tensile irons capable of responding to flame hardening.

all the best Madass: put the effort into the design and focus on the cush drive feature.
kind regards
Bradley

hello madass
just read post regarding shrink fit sporcket.

mate, the width is only about 3/8th. do you think a 10 thou shrink would hold at extremes. if some realised that a interference fit was all there was, I would bet they would try their damndness to break it. human nature and the pitfalls of manufacturing. you would need to calculate the fit so as not to put too much compressive stress into the hub and actually undo and loosen the fit. the hub is only very thin in the wall. seem to be up against it regarding a replaceable sprocket.

also if the sprocket is surface hardened, the heat required to expand the sprocket would not be able to go above 150 degrees C. I doubt yo would get 10/15 thou at this temp. other wise the sprocket may start to be tempered some more. so if you cant get enough expansion by heat to this temp, keep the sprocket cold and freeze the hub.

I keep getting drawn back to a one piece unit. iron or steel. I would go with steel because it is known to work therefore less development effort and costs.

just me 2 bobs worth
Bradley

Bradley your 2 bobs worth is actually worth more, you're on the ball, and I do agree with you that one piece steel is the best option, I'm just tossin round some ideas, when I get time I'll start talking to some foundries.
a lot of the foundries dont just cast, they will do complete processing, heat treatment, machining etc.

hello Madass

one final thought. do you really need to have a casting. k1045 is available as hot rolled bar stock. if you had blanks cut, could you not machine the whole damn thing in a powerful CNC. why, if the cnc had live tooling, it would take about 45mins to do all the machining, 1 hour at the most. ypu could do all the machining except the final brake drum bore. the spider side, bearing bores, OD and tooth cutting could be done after normalizing the hot rolled blank.

after hardening the teeth , just temper and finish the brake drum bore (on a mandrel or in soft jaws)and game over. same process as previous post but this takes the complexity of a casting out of the equation,the economics of this method may be worth further study. you would still have a high quality product.

also for wear considerations, tell customers to use a hunting ratio in the final drive

all the best
bradley