BO15 4-4-2

[sandman]

Nascar banned the Superbird, Daytona, and all the other aerodynamic cars for the 1971 season. NASCAR officials were concerned with the dangerously high speeds as well the huge wing and nose cone as the cars didn't look much like a stock car. The ban brought an end to the production of the Plymouth Superbird . LOL

 

[wheelbender6]

Some of the latter 442s had 400 ci engine, 4 bbl carb and dual exhaust. I dont know which years.

 

[Wildcat]

I'm still working out plans for the drivetrain. I realized the chain must have some slack when shifting back to the larger chainwheel, so more engineering is required to take up the slack in the chain once in high gear. I had only been considering the slack when in low range. With a coaster brake that presents a challenge. I have a few ideas that may work, but I'll need at least one more roller added to the drivetrain.
Then I saw this thing in a post by MattiThundrr. It's called a Double Double. It gives a bike low range and high range by changing the chain between chainwheels and cogs for when you want to go offroad and need to drop down.

The chain is one length and doesn't need a tensioner or a roller. It has a low and high range, 2 speeds. The cogs and chainwheels are sized to use the same length chain. Genius!

With my 2 speed hub, that would make 4 speeds. I need to figure how many teeth the extra cog will need to do the same thing. I have a 42 and 36 up front and a 22 in the rear right now. How many teeth should the other cog have? I'll need a few hours to figure it out.
I already have the chainwheels worked out, but the rear hub is a new idea. The rear cog is concave like the chainwheels. The hub comes with 2 washers that go on either side of the cog. Both of them are the same thickness as one cog. I plan to get another cog, also concave to give clearance for the chain on either cog, face it inward and leave off the washers. Depending how well it sits, I may have to add a washer or make some room somehow to get the lockring on.

Then I'll have four speeds but will have to loosen the rear wheel to make the shift up or down. The Double Double is made for use with quick release wheel, making it fairly easy to change gears. I'll have to carry a wrench and screwdriver to shift. But not having to worry about a roller or tensioner giving out makes this look pretty good.

 

[Chad T]

Starting to look like a plan. That should work. Just get yourself a nice gear wrench to keep with the bike. Good excuse for a nice tool bag too.

Thought of you the other day when I saw this. It's an early racing bike that shifts with no tensioner. One lever loosens the wheel and the other pushes the chain over. Supposedly actually worked well. Axle has splines that engage the teeth on the dropout to keep the axle straight.

Apparently they actually shifted these on the fly. Can you imagine going down a hill at 40 mph and loosening your back wheel to change gears? That's when men were men.

 

[Wildcat]

You would have to work both levers one handedly at the same time! Would the rider have to take his weight off the rear wheel when shifting? I see me having big problems at any speed on that.

I ran the numbers and remembered I'm going to make dropout extensions. The slot for the rear wheel can be long enough to take up the 3 inches of chain slack by sliding the wheel further rearward.
I did figure out the 2 cog system though. If one cog was 18 teeth and the other 24 teeth with 36 and 42 chain wheels, then the chain would be the same length with the wheel in the same spot. Gear Inches would be 42-60-65-90.
By just having more dropout to work with, then I stay with one cog and have 46-54-63-74 gear inches.

 

[Wildcat]

I'll still try to mount two cogs on the hub to see if it's doable. I could possibly have 8 speeds. That might require a 6 inch slot in the dropout. I'll do some more calculating.

 

[Wildcat]

I played my usual word games and crosswords when this came up. It must be a sign:

So I went back to work figuring out the gears. The dropout slot needs to be about 5 inches long to adjust the wheel for 7 inches of chain slack if I went extreme, 36/44 chain wheels with 18/24 on the cogs.
The gear inches for that would be 42-94 as an 8 speed. I will go less radical, with 36/42 up front with 20/22 in back. All I need is a 20 tooth cog that is concave. That would give me 46-81 gear inches with 8 speeds, 46-71 with 4 speeds if only using a single 22 cog. I have some old Sturmey Archer hubs with 18 tooth cogs. If I use one of those with my existing 22 cog, then I'll have 8 speeds with a 46-56-63-77 low range and a 53-65-73-90 upper range. The dropout slot to handle that 36/18 and 42/22 would be at least 3 inches long.
Here's all my calculations.

 

[Wildcat]

My new lucky 7s showed up today. 42 and 36. As they sit together, they may have enough clearance for the chain but I have washers to make it work if not. The concave design makes it possible. I can't check it because all my chains have already been shipped out. I may also do like I have on my other bikes and put a backing plate behind them for looks, either brass or copper.

 

[kingfish254]

I'm still working out plans for the drivetrain. I realized the chain must have some slack when shifting back to the larger chainwheel, so more engineering is required to take up the slack in the chain once in high gear. I had only been considering the slack when in low range. With a coaster brake that presents a challenge. I have a few ideas that may work, but I'll need at least one more roller added to the drivetrain.
Then I saw this thing in a post by MattiThundrr. It's called a Double Double. It gives a bike low range and high range by changing the chain between chainwheels and cogs for when you want to go offroad and need to drop down.
View attachment 126753
The chain is one length and doesn't need a tensioner or a roller. It has a low and high range, 2 speeds. The cogs and chainwheels are sized to use the same length chain. Genius!

With my 2 speed hub, that would make 4 speeds. I need to figure how many teeth the extra cog will need to do the same thing. I have a 42 and 36 up front and a 22 in the rear right now. How many teeth should the other cog have? I'll need a few hours to figure it out.
I already have the chainwheels worked out, but the rear hub is a new idea. The rear cog is concave like the chainwheels. The hub comes with 2 washers that go on either side of the cog. Both of them are the same thickness as one cog. I plan to get another cog, also concave to give clearance for the chain on either cog, face it inward and leave off the washers. Depending how well it sits, I may have to add a washer or make some room somehow to get the lockring on.
View attachment 126755
Then I'll have four speeds but will have to loosen the rear wheel to make the shift up or down. The Double Double is made for use with quick release wheel, making it fairly easy to change gears. I'll have to carry a wrench and screwdriver to shift. But not having to worry about a roller or tensioner giving out makes this look pretty good.

That double double idea is cool, but can you attach a threaded chainwheel on that SA hub?

 

[kingfish254]

My new lucky 7s showed up today. 42 and 36. As they sit together, they may have enough clearance for the chain but I have washers to make it work if not. The concave design makes it possible. I can't check it because all my chains have already been shipped out. I may also do like I have on my other bikes and put a backing plate behind them for looks, either brass or copper.
View attachment 126802
View attachment 126803

I still have one of your copper/brass backing plates? Do you want me to ship it to you?

 

[Wildcat]

Pm sent!

I'm not using a threaded cog. I'm adding another cog like the one that comes with it. Same as a one speed or three speed cog. The old hubs I have have 18 tooth cogs. I'm hoping there is enough space so both cogs fit and are solid with no slop. It's a try it and see if it works thing.

 

[kingfish254]

Pm sent!

I'm not using a threaded cog. I'm adding another cog like the one that comes with it. Same as a one speed or three speed cog. The old hubs I have have 18 tooth cogs. I'm hoping there is enough space so both cogs fit and are solid with no slop. It's a try it and see if it works thing.View attachment 126826

I don't see how two of those cogs can slide on the hub and not stick up higher than the lip that the retaining ring needs to slide into.


BTW, I pulled out the copper plate and will get it shipped to you this week. Pretty cool to see the paisley on it.

 

[Wildcat]

I don't see how two of those cogs can slide on the hub and not stick up higher than the lip that the retaining ring needs to slide into.


BTW, I pulled out the copper plate and will get it shipped to you this week. Pretty cool to see the paisley on it.

View attachment 127027

That's a CWC pattern (Monark too with standard teeth) for sure. Here's what it looked like back in 2013. When I trim it to fit the 36 tooth lucky seven sprocket I'll make a nicer cut:

 

[Wildcat]

"I don't see how two of those cogs can slide on the hub and not stick up higher than the lip that the retaining ring needs to slide into."

The hub came with a 22 tooth cog and 2 washers that go on either side of the cog with the o ring going on last. I'm guessing the width of both washers is the same as the width of a cog. Everything has been shipped out so I can't check them.

I don't think it will matter which cog goes on first, the chainline should be fairly long.
It could be that even if they go on the hub ok, they will be too close together for the chain to work without contacting the opposite cog, even though they are facing away from each other. In which case, I'm back to only 4 speeds.
But the chain is sold as 1/8" wide so it should all work just fine! I think the chain is wider than 1/8" though.

 

[kingfish254]

That cipherin sounds good to me!

 

[Chad T]

But the chain is sold as 1/8" wide so it should all work just fine! I think the chain is wider than 1/8" though.

The outside of the chain is wider than 1/8. The 1/8 part is the inside dimension of the narrow links.

 

[Wildcat]

Perfect! I was looking for just that thing the other day and couldn't find anything. I did another search and now have found tons of info. The ads all say my new chains are 9.3mm, or .367 of an inch wide, just under 3/8ths inches wide overall. 3/8ths is .375 inches. So I'll need to clear half of that on the smaller cog and smaller chain wheel.
I checked the two lucky sevens, the teeth are just 3/8ths of an inch apart as they sit together. So I'm pretty sure they will get a washer between them.

 

[Wildcat]

I found a build that uses dropout extensions and springer fork extensions that I am going to try to do. This is from a thread here back in the 2009 annual buildoff. Dangratsdan's bike, Starliner.

He fit a 3" tire in a middleweight Murray frame with these extensions. This brought to my attention the chain line clearance with 3" tires. Something else I forgot to consider on my driveline. I don't think the inner chainwheel will line up with the inner cog and not have tire rub. Maybe only one cog concaved outward to get clearance. Back to 4 speeds.

I like how the dropout flows with the frame. I'll need a longer slot for the axle but it should follow the curve of the dropout and not be a straight slot.

This is what I had thought of, only this is a rattrap springer. The flanges move for the springer action. Mine won't have to, being a knee action springer, so I'll have more leeway in the fabrication.

 

[Wildcat]

I'm under a month to get to my new home if they don't cancel flights again. Here's an old ratty 442 just for fun:

 

[Chad T]

Like how he uses the incline of the driveway to hold the car in place for the burnout. Kind of a hillbilly line lock.