Steal on a Ducar 212

[Rat]

If you only have 1 vent tube, you only need 1 check valve.

I jus put my son's ducar 212 on my grandson buggy. Put the stock carb and muffler on it, turned it down to 4800 max rpm, and switch valve covers for 1 check valve.

View attachment 144978
View attachment 144979

Pretty sure @Denny would argue 2vs1 breather tube checks

Oh wait, he does CONSTANTLY

Also that looks like a wedge on yours like my 208, not a Hemi like the Ducar 212 I've got not that the head type matters any for maintaining a negative case pressure

 

[BrownStainRacing]

Pretty sure @Denny would argue 2vs1 breather tube checks

Oh wait, he does CONSTANTLY

Also that looks like a wedge on yours like my 208, not a Hemi like the Ducar 212 I've got not that the head type matters any for maintaining a negative case pressure

I run 2 on my 224, but it stays above 5000 rpm alot more.1 check valve for each vent.

It is a wedge head, small chambered (14.5cc), small valve head (25/24mm).

It's 10.1:1CR, cm cam, 26# springs. Had a .615" no go ruixing carb, I put the stock ruixing back on it for the kid. He don't need to be above 40 mph on these old logging roads.

 

[Rat]

I went and pulled the numbers for the wheel gear cluster
34, 24, 22, 20, 18, 16, 14

I also took inventory of what I have that I can work with to adjust the ratios with.

50 (spider for a secondary gear 2 of the 3 40t fits)

48/38/28 (MTB riveted triple)

All loose singles
46×2
44×2
40×3
30 (Goes with the spider I'm using for the 52t)

 

[BrownStainRacing]

I went and pulled the numbers for the wheel gear cluster
34, 24, 22, 20, 18, 16, 14

I also took inventory of what I have that I can work with to adjust the ratios with.

50 (spider for a secondary gear 2 of the 3 40t fits)

48/38/28 (MTB riveted triple)

All loose singles
46×2
44×2
40×3
30 (Goes with the spider I'm using for the 52t)

Very interesting, .

Can't wait til you get it moving on its own.

Those are more gears then I care to work with,

I have enough trouble, figuring out 1 ratio.

 

[Rat]

Very interesting, .

Can't wait til you get it moving on its own.

Those are more gears then I care to work with,

I have enough trouble, figuring out 1 ratio.

Lmao, I'm just crazy enough to make it work... but so far there's no one else that's piped up on the matted of the Ducars ability to make scary power

 

[Rat]

I have enough trouble, figuring out 1 ratio.

So I've done the heavy work for you then.
After taking inventory and running though a jackshaft calculator intended for electric scooters and such (rpm is rpm, and gear ratios are gear ratios, the PowerPoint providing is irrelevant)
I've determined that TC (10t) to 52t input, 28t output to 7 final gears on 26" comes off as follows at 3800 rpm
10~52~28~__

34= 6.31 [46.73mph]
28= 5.2 [56.7mph]
24= 4.46 [66.11mph]
22= 4.09 [72.09mph]
20= 3.71 [79.48mph]
18= 3.34 [88.28mph]
16= 2.97 [99.28mph]
14= 2.6. [113.41mph]

I don't know of anyone here that knows the 6" 30 series better than you so I'm just preemptively looking for issues at this point.

I certainly have no intention of trying to exceed 45/50mph and probably will never have room enough for better than 40, I absolutely would never trust even top shelf quality bicycle tires above 60mph
(I've proven a few can in fact handle that much centrifugal force without ballooning off the rim bead)

This calculator determines the top speed of the vehicle with no margin for mechanical, rolling, or wind resistance. These resistance factors could make the top speed slower than the calculation. The amount that the top speed will be reduced by resistance depends on many factors such as the power of the motor, weight of the vehicle and rider, size and air pressure of the tires, incline degree that the vehicle is going up, and headwind. The top speed could also be increased above the top speed calculation by riding down hill, or riding with a strong wind against your back.
When riding on flat ground the top speed is usually only reduced by a small amount.

 

[BrownStainRacing]

So I've done the heavy work for you then.
After taking inventory and running though a jackshaft calculator intended for electric scooters and such (rpm is rpm, and gear ratios are gear ratios, the PowerPoint providing is irrelevant)
I've determined that TC (10t) to 52t input, 28t output to 7 final gears on 26" comes off as follows at 3800 rpm
10~52~28~__

34= 6.31 [46.73mph]
28= 5.2 [56.7mph]
24= 4.46 [66.11mph]
22= 4.09 [72.09mph]
20= 3.71 [79.48mph]
18= 3.34 [88.28mph]
16= 2.97 [99.28mph]
14= 2.6. [113.41mph]

I don't know of anyone here that knows the 6" 30 series better than you so I'm just preemptively looking for issues at this point

Is the 52t the biggest you have, or can fit there????

Is the 28t the smallest you have that can fit there???

 

[Rat]

Is the 52t the biggest you have, or can fit there????

Is the 28t the smallest you have that can fit there???

52 is the biggest I have that will work, I don't believe I can get bigger than 55 (roadbikes) at all without fabricating.
If I fabricated the largest I can go would be a 60t but then I have the potential issue of it being too close to the TC. I won't know exactly what clearance I have until I get the ordered parts... unless I pull off the running gear on my 208 for mockup

28 is the smallest I have on hand, and without fabrication don't believe I can do smaller.

If I fabricated I could use a section off a 5/8" trike axle (or an 8" jackshaft made for karts) and expand my options by any cog I can throw money at or get an adapter for... it absolutely must be 1/2 pitch, double roller or leave me room enough to make it a double to tie the FFW crankset (44t) into the rest of the drivetrain

As is the spindles are set up 3/4" shaft and bearing, stepped to MTB standard 5/8-1/2 square taper... an awkward factory method of using "American Bottom Bracket" shell with cup and cone, but mount "Euro Bottom Bracket" square taper cranksets

 

[BrownStainRacing]

52 is the biggest I have that will work, I don't believe I can get bigger than 55 (roadbikes) at all without fabricating

28 is the smallest I have on hand, and without fabrication don't believe I can do smaller.

If I fabricated I could use a section off a 5/8" trike axle (or an 8" jackshaft made for karts) and expand my options by any 3/4 bore cog I can throw money at or get an adapter for.

As is the spindles are set up 3/4" shaft and bearing, stepped to MTB standard 5/8-1/2 square taper... an awkward factory method of using "American Bottom Bracket" shell with cup and cone, but mount "Euro Bottom Bracket" square taper cranksets

Ok, gotcha.

It would be better with a 9t for the t/c jackshaft and use the sprockets you have now.

I would definitely try what you have 1st, because the big 26" tire and those others gears are new to me.

Here's what I do when I set up gear ratio on a mini bike.

Usally a 19" tire, for the trails around here.

I start with the rider weight, lets say 200#.

Then I move to the max torque of the engine, the Ducar 212 is around 10 ft lbs, being stock form.

I will try to get 200 ft lbs of torque ( same as riders weight) to the tire, to get the weight moving 1st.

After you get the weight moving up outta the hole, then its easier on the t/c and engine.

The 30 series (6" driven) is 2.7:1 on the low side.

200 / 2.7 = 74

74 / 10 = 7.4 :1

7.4:1 is by no means written in stone, but it would be where I would start for a 200# rider, with a 19" tire, for trail busting, ridge running, mud hole stomping, jus plain good ol fun time mini biking, and it would still hit 40-45 mph on a flat level straight run with the stock Ducar 212.

Now with your 26" tire, you have to do a lil more math.

The math I got with 7.4:1 gear, .9:1 (high side of 6") would be 42 mph at 5000 rpm.

It doesn't mean it will hit 5000, I'm jus looking for that 42.

With the 26" tire, I would keep adding gear to the calculator til I can get 42 mph, it's gonna be alot more gear to add, but it's gonna pull up outta the hole faster, get to max HP faster, and get to max rpm and speed in a shorter distance.

So I would try starting off with a 10:1 gear with a 6" driven to get to the 42 mph mark.

A 7" driven is 3.13 low side, and 1.12 high side, you can do the math, I'm trying to eat

But again, like I said, I would try what you got 1st.

I've been wrong plenty of times and jus something simple like a 1 " smaller or bigger tire can make a big difference, a lil more or less stall in the driver will too.

When you start upgrading the engine to bring in more torque in the same rpm range, with CR, faster ramped cams, smaller valves, then you will be dropping gear to keep the same 200 ft lbs torq to the tire.

Jus an increase of .5 more ft lbs torque, outta the engine, will need a gear change.

Unless you like going the same max speed in a shorter distance,

But you got those other gears on the wheel sprocket(s) for plenty of top speed.

Getting that low side is gonna be the tricky part. After you get the low side dialed in, the high side jus falls into place.

Make sense???

If not, lmk

 

[Rat]

Ok, gotcha.

It would be better with a 9t for the t/c jackshaft and use the sprockets you have now.

I would definitely try what you have 1st, because the big 26" tire and those others gears are new to me.

Here's what I do when I set up gear ratio on a mini bike.

Usally a 19" tire, for the trails around here.

I start with the rider weight, lets say 200#.

Then I move to the max torque of the engine, the Ducar 212 is around 10 ft lbs, being stock form.

I will try to get 200 ft lbs of torque ( same as riders weight) to the tire, to get the weight moving 1st.

After you get the weight moving up outta the hole, then its easier on the t/c and engine.

The 30 series (6" driven) is 2.7:1 on the low side.

200 / 2.7 = 74

74 / 10 = 7.4 :1

7.4:1 is by no means written in stone, but it would be where I would start for a 200# rider, with a 19" tire, for trail busting, ridge running, mud hole stomping, jus plain good ol fun time mini biking, and it would still hit 40-45 mph on a flat level straight run with the stock Ducar 212.

Now with your 26" tire, you have to do a lil more math.

The math I got with 7.4:1 gear, .9:1 (high side of 6") would be 42 mph at 5000 rpm.

It doesn't mean it will hit 5000, I'm jus looking for that 42.

With the 26" tire, I would keep adding gear to the calculator til I can get 42 mph, it's gonna be alot more gear to add, but it's gonna pull up outta the hole faster, get to max HP faster, and get to max rpm and speed in a shorter distance.

So I would try starting off with a 10:1 gear with a 6" driven to get to the 42 mph mark.

A 7" driven is 3.13 low side, and 1.12 high side, you can do the math, I'm trying to eat

But again, like I said, I would try what you got 1st.

I've been wrong plenty of times and jus something simple like a 1 " smaller or bigger tire can make a big difference, a lil more or less stall in the driver will too.

When you start upgrading the engine to bring in more torque in the same rpm range, with CR, faster ramped cams, smaller valves, then you will be dropping gear to keep the same 200 ft lbs torq to the tire.

Jus an increase of .5 more ft lbs torque, outta the engine, will need a gear change.

Unless you like going the same max speed in a shorter distance,

But you got those other gears on the wheel sprocket(s) for plenty of top speed.

Getting that low side is gonna be the tricky part. After you get the low side dialed in, the high side jus falls into place.

Make sense???

If not, lmk

Mostly makes sense, I just finished knocking off the cruddy looking (but very solid and functional) double roller 36t off, modified the 48/38/28 chainring set (cut the pedal leg off and ground the center down concentric) so the pedals go 44 to 48 to rear.

The jackshaft is 52 to 28, I have contemplated pulling the 9t off to put the 10t back on my 208

 

[BrownStainRacing]

Mostly makes sense, I just finished knocking off the cruddy looking (but very solid and functional) double roller 36t off, modified the 48/38/28 chainring set (cut the pedal leg off and ground the center down concentric) so the pedals go 44 to 48 to rear.

The jackshaft is 52 to 28, I have contemplated pulling the 9t off to put the 10t back on my 208

Is this the 1st time you've tried a build like this with those type of sprockets and chain???

I'm asking, because jus from the engine, t/c, and primary you will be hitting the secondary chain and sprockets with around 140 ft lbs torq.

You think it'll hold it????

Then there's the rear hub with spokes???

With jus what you have now 10t-52t, 28t-34t, that's gotta be around 170 ft lbs at the hub.

170 is not enough for a 26" tire and 200# rider, but......it might be too much for the hub.

Idk, I've never tried anything like that.

 

[Rat]

Is this the 1st time you've tried a build like this with those type of sprockets and chain???

I'm asking, because jus from the engine, t/c, and primary you will be hitting the secondary chain and sprockets with around 140 ft lbs torq.

You think it'll hold it????

Then there's the rear hub with spokes???

With jus what you have now 10t-52t, 28t-34t, that's gotta be around 170 ft lbs at the hub.

170 is not enough for a 26" tire and 200# rider, but......it might be too much for the hub.

Idk, I've never tried anything like that.

I've done similar but due to other circumstances had to abandon ship on the project (too much to break down and put into a moving truck already fast out of room)

It was a 1978 Ret-Bar 2wd factory trike kit from a 1979 Schwinn Town and Country 3speed which if your not familiar used a Shimano 3cc coaster hub (no spoke flanges) and a gear welded to center as a jackshaft (and 3 speed) to turn the Ret-Bar.

I took a wiped out CR70, cut up the frame and used the engine mounts to then mount the 70cc 4speed into a different highly modified frame (still have the 79 Schwinn main frame assembled as a Hollywood clone)
I widened and lowered the rear by relacing the factory 28 spoke hubs into a pair of JCHiggins 20" rims with 1 gauge spokes (from 24x1⅜ S6 rims) and stuck 20x3 slicks on which took the rear track from 32" to 38" wide. I then forced the center of gravity by using a longer front fork with a 26" wheel.

I got a few rides in under it's own power before I began to refine and tune it and despite less chain lengths involved it was a very similar set up in the respect that the 4speed was chained to one end of the jackshaft, the other end was chained to the crankset, and the crankset was otherwise normally ran to the original jackshaft hub, jumped from center to the axle.

I only ever busted one chain and it was a cheap Chinese painted thing and never broke another.

Keeping in mind I was also pushing it hard trying to break something after getting better quality chains on it and had it up to 45 mph a few times without ever really getting it topped out, as well as coasted it up on 2 wheels at lower speeds to see what degree of twisting I might have. I took it around a couple corners much harder than I would have on the original 1979 geometry... but I'm also of the generation that rode Honda ATC's new before they were outlawed so I know to hike up on the seat ready to hang off the outside of corners and/or drift to stay shiny side up while cornering at stupid speeds.

Yea, I'm a bit crazy but I have fun doing what shouldn't be done, and what some say Can't be.

 

[Rat]

I'm not too worried about it holding or not holding, that's half the fun for me.

If the 52 has too much deflection, I have another 52t that I can tack weld to the one I'm using to add rigidity to it.

I don't forsee deflection in the 28t because it's teeth are quite close to the rivets so there's no room for it to go anywhere.

As for the rearset on the hub, again I'm not too concerned... the hub idk it's aluminum the freewheel threads will hold or they won't. If they don't then whatever I'll build a different wheelset which I may do anyway because I have never seen a matched F/R pair of 48 spoked wheels larger than 20", 24" and bigger is always front only.

If I need to build different rims then I will very likely widen the rear and do away with the jackshaft since the entire sole purpose was to use the exsisting wheelset, shiftable gears was simply a bonus reward.

I might end up building a pair of stout wheels for the sole purpose of adding disc brakes alone.

 

[Rat]

I preemptively checked the thickness of the 52's will be stacked, and I will probably be tacking those together just for piece of mind due to chain width in comparison

The two sprockets together they are JUST under the width of a #41 so I will confirm 415 fitment before I pull the trigger on it (litteraly)

 

[Rat]

If I tack the 52's I will have to peen the teeth towards each other due to a gap I cannot reconcile caused by a ridge I don't want to grind off.

I decided to pull parts off my 208 to get ahead with mock-up before parts arrive and make adjustments accordingly. I'll be using the 9t I mocked up with and going back to a 10 for my 208.

Officially I'm not clearing larger than a 56t assuming I can find one with a BDS that matches the spider.

 

[BrownStainRacing]

That 56t 9t, (6.22), with the 34t 28t (1.21) on the other side is 7.52:1, that's about 33 ft lbs more trq to the tire, then the 52t 10t.

Imho, it's still not enough for a 26" tire, but I'd try it and see how everything gonna work together,

 

[Rat]

That 56t 9t, (6.22), with the 34t 28t (1.21) on the other side is 7.52:1, that's about 33 ft lbs more trq to the tire, then the 52t 10t.

Imho, it's still not enough for a 26" tire, but I'd try it and see how everything gonna work together,

No... 9, 52, 28, 34

The biggest I'd be able to clear would be 56 if I could find one to make work, and I know for a fact that by itself 10/56 will move 26" tires although a little hard on the belt.

I am considering dropping it onto smaller rims to use wider tires though. I don't have the ground clearance for smaller than a 24" and the stuff to build a pair of 18" will be more than I've got into the whole thing already

 

[Rat]

I'm going to assume you're preemptively calculating in the 6" 30 series as well
Because I'm getting 7.02

 

[BrownStainRacing]

I'm going to assume you're preemptively calculating in the 6" 30 series as well
Because I'm getting 7.02

7.02 x .09 = 6.31:1 final drive.

I doubt the t/c will ever go into high. Which will be good for not lugging the engine.

Have you tried it out yet ????

 

[Rat]

7.02 x .09 = 6.31:1 final drive.

I doubt the t/c will ever go into high. Which will be good for not lugging the engine.

Have you tried it out yet ????

Still waiting on the new hardware, I pulled the beat up 30 series for mockup and to get things shimed and sured so that I can pretty much bolt on and test without an hour or more fiddling with it.
We've got a winter warm snap this week so I should be able to do some testing although I have tested as a regular bicycle pedaling and shifting it with the added weight of a Briggs sitting in there... it handles surprisingly well and pedals shockingly easy.

Dropping it onto 24" wheels tires is only going to drop the axle center 1" closer to the ground which is basically the same as running 2.50-18 motorcycle tires (23.89 rolling diameter) without the additional wheel and tire weight.

I am a little bit concerned about one issue in particular cropping up that I had with my 208 though, and that would be having enough power out of the hole (as well as brake force) that the tires decide to slip the rim bead and tear the valve stem off the tube. Thankfully they never let go while I was riding (kept finding a flat the next day) and about 10 tubes later I got a killer deal on a 18×185B Takasago rim identical to one I already had allowing me to build a matched wheelset that wouldn't be able to do that.

Damn rims to build on are expensive, but I know a few circles I could probably bank from.