frame design questions regarding tanks, motor

[still2nu2no]

new to the forum, so please be a little patient (particularly if this is posted in the wrong section).

One think that continues to bother me is the styling and location of many of the tanks included or used in doing a conversion. They look horrendous. I understand they may be similar to the old Whizzer style tanks, and that's OK if you're building a Whizzer look-a-like, but many of the powered bikes seen here (and elsewhere on the Internet) have been custom constructed. Doesn't it make sense for some of the kit makers to offer a tank option or the kits without a tank?

I'd riden a Sachs rear motor/hub/rim conversion years ago and it used a 1 litre MSR backpacking fuel container for fuel, which was mounted in a bottle cage. I have to believe that something can be accomplished that looks better than the Whizzer tanks. Why not mount a tank below the top tube? It would look cleaner.

I feel the same way about motorcycle tanks: on choppers there is always a huge amount of space under the top tube.

Obviously those bikes designed and built to emulate board trackers often use tanks hung from the top tube. This just makes more sense to me.

Regarding motor locations, I see several types of mounting: rack mount, "high mount" where the engine is well above the crankset, and "low" mount, where the downtube is modified to allow the motor to be mounted slightly above or inline to the crankset. (as referenced to the centre-line of the output sprocket). I guess my question is that if a dedicated design is used rather than a retro-fit, why wouldn't the downtube/motor mount location be made to lower the centre of gravity. I understand that in the case of mountain/offroad bikes the need for ground clearance affects motor location, but what about street/cruiser bikes?

Again, these questions and comments are not meant to inflame anybody, but rather to help educate myself. No offence is intended towards anyone or any particular bike style.

thanks for your patience with a noob

 

[motorpsycho]

i agree with you on the gas tank design, but with a little work, they can look really cool.
on the other hand, you can make your own custom gas tank if you know how to do it.
I'm not talking about a water bottle or p.v.c. made gas tank...I'm talking about a full custom frame mounted tank that actually looks like a gas tank.
my lowrider gas tank, which is the stock kit tank, painted metallic white with pearl clear, ivory and purple pinstriping.

the tank on my o.c.c. chopper, custom made from a jesse james bicycle gas tank.

 

[Porkchop]

Keep in mind, most of the engine kits come from China and I imagine they're disigned and made for their market, not ours or the rest of the world. Keep wandering around here on the forum, espeically the photo gallery. There are some good looking tanks around. Find something you like and start asking questions.

 

[Porkchop]

As far as some of the things you mentioned about "Center of Gravity" I personally have a friction drive set up, with the engine hanging on one side above the rear wheel. I have never noticed being off balance. The engine weighs only maybe 15 pounds or less. I don't think it's of any real concern. If we were talking a mega dollar high performance machine of some type, yes, it probably would be. Not trying to talk you into a friction drive, just saying I think balance is a critical issue here. Just use good sense and most of all, at least try to be safe. Welcome aboard the forum !

 

[still2nu2no]

guys, thanks for the replies

i agree with you on the gas tank design, but with a little work, they can look really cool.
on the other hand, you can make your own custom gas tank if you know how to do it.
I'm not talking about a water bottle or p.v.c. made gas tank...I'm talking about a full custom frame mounted tank that actually looks like a gas tank.
my lowrider gas tank, which is the stock kit tank, painted metallic white with pearl clear, ivory and purple pinstriping.

Yes, on the right bike, some of the engine kit tanks look right. Yours looks very good.

Keep in mind, most of the engine kits come from China and I imagine they're disigned and made for their market, not ours or the rest of the world. Keep wandering around here on the forum, espeically the photo gallery. There are some good looking tanks around. Find something you like and start asking questions.

Definitely!

As far as some of the things you mentioned about "Center of Gravity" I personally have a friction drive set up, with the engine hanging on one side above the rear wheel. I have never noticed being off balance. The engine weighs only maybe 15 pounds or less. I don't think it's of any real concern. If we were talking a mega dollar high performance machine of some type, yes, it probably would be. Not trying to talk you into a friction drive, just saying I think balance is a critical issue here. Just use good sense and most of all, at least try to be safe. Welcome aboard the forum !

I guess the CofG thing is my background in physics. It makes sense to keep it low, but the point made regarding the mass of the engine , and its distance to the CofG vs. mass of bike/rider and their CofG isn't wasted. I guess if "custom bikes" are being built from scratch or if one is modifying a existing bike, it seems to me to try to optimize this in the design. In the gallery I saw a bike that started as a "ladie's" bike and ended up as quite a nice board tracker, with low-slung engine as per many of the originals.

The current bike in my garage is a WCC/JJ "chopper" with gas tank. It looks very good and will not need much in terms of modifications to have functional. This bike belongs to a friend who has lent it to me . It's a 38cc Poulan Pro 2stroke single from a chainsaw with a centrifical clutch It is currently friction drive, using a welded mount for a jackshaft/roller, and the engine. I'd like to make a new engine mount. Chain is far more efficient at transfer of energy (obviously "reduced friction). Peak power in the 6000 RPM range (I'll see if I can get specs from Poulan). I'd like to gear it for maximum efficiency at 25 mph (40 kph), to try to keep it somewhat "legal". I may not even be permitted to use it on the street after all is said and done.

motopsycho: Your bike looks excellent, what I hope to end up with (and maybe a "board tracker" style one too)

 

[still2nu2no]

found the gallery of the simple board tracker I liked.

the board tracker I saw was from James65. The gallery here sucks! Why not just a photobucket type "thumbnail?

motorpsycho: 3 piece cranks on the OCC? if so stock? if not, just a common bottom bracket?

About your chain drive, motor to jackshaft (inner) and crankset (chainring) to jackshaft and sprockets (rear)? Am I seeing this right?

thanks

 

[Big Red]

Tanks, motors.

I'm also building a Jesse James M.B. Almost finished, just waiting on carb jets to get the engine running right. But I'm the old school guy. I like it to look like an old school motorcycle with the engine set high in the frame and the tank mounted on the top bar. Mounting the engine high required me to put a side draught carb on it, but it looks cool. I'll try to shoot pics when I'm done.
So fabricate away bro, Make it YOUR bike. The only real requirement is that it's safe. I don't know what state you're in, so I can't comment on the law for you. In California it's 49cc and 30mph limit. Look up the law for your state and follow it as closely as possible.(or not?).
Good Luck,
Big Red.

 

[motorpsycho]

motorpsycho: 3 piece cranks on the OCC? if so stock? if not, just a common bottom bracket?

thanks

yes those 3 peice cranks are stock, and the bottom bracket is small in diameter, much like some mountain bikes with 3 peice cranks.
I have no idea of the diameter, but it's very small compaired to the bottom bracket on bikes with one peice cranks.

 

[motorpsycho]

Yes, on the right bike, some of the engine kit tanks look right. Yours looks very good.

The current bike in my garage is a WCC/JJ "chopper" with gas tank. It looks very good and will not need much in terms of modifications to have functional.

the gas tank on my o.c.c. is from a Jesse James chopper.
There is A LOT of work involved in making these gas tanks functional.
You have to weld up, braze or silver solder all of the holes and gaps closed.
then you have to make fuel outlet tubes (one on each side of the tank).
You have to put one on each side because the tank tunnel is so high inside the tank, there's no way for gas to get from one side to the other. It's actually like 2 tanks inside a single tank. Then you have to run 2 fuel lines out of the tank with a filter in each line. Run the lines into a T fitting so that you have 2 lines in and one line out. after the T fitting you can put an in-line fuel shut off valve on the single gas line, and then run a line from it to the carb.

you have to pressure test the tank with compressed air and water to make sure there are no leaks at all. If there are leaks, then you have to go back and re-seal them by welding, brazing or silver soldering them. Then test it again....and repeat if necessary.
cut a hole in the top for a gas cap, and then figure out a gas cap that will work (i have a simple solution for this), paint it, and figure out a way to mount the tank to the frame (i made a hidden mount).
if you want to go a step further like i did, grind down the big ugly weld in the front of the tank where the peices are welded together, fill that area in with bondo, smooth it out and slightly re-shape the front of the tank.
you can also fill the little dents in the tank with bondo to smooth them out, These tanks ALL have little dents from when they were made.
the steel that these tanks are made out of is very thick and heavy, so they do make excellent real gas tanks.

 

[Big Red]

Gas Tank

Hey Moto, When I first hit this site and saw your bike, I asked where you got your tank. Further investigation showed me it came 0ff a Jesse James and that you're a pretty fair fabricator. As you know, I'm doing a JJ now, but it had no tank on it when I got it. The stock tank fits it perfectly and wish I had one. But, I just don't have the welding equipment even if I did.
I think you have one of the best looking OCC Choppers around, in large part due to the tank. I would just have to change the seat to a larger, more comfortable one,(Couse I'm old). I might also find a fork set with the brake setup on it. Put on a dual pull and yer done. I had one setup like that and the braking was incredible. Still, Great job on the bike.
Big Red.