How much space

[chainmaker]

I am building a tadpole based on Atomic Zombies warrior plans, and I am going to put a HT66 cc motor on it I will have begun building the frame before I get the motor. I will be mounting it on a "tail"(an extension of the frame) behind the seat. My seat back will be at 45 degrees, the question I have is I need a rough idea of how long of a "tail" to plan for between the seatback and rear tire for the motor and a jackshaft. What are the dimensions of the motor with exaust, and carb. I ordered the motormount from Manic Mechanic today and I am going to mount the flat bottom part to the "tail" I am using 1.5 x1.5 square tube so I think this will work out nice. I saw somplace a outline of a HT motor with a measurment across it, You were supposed to re-size it and print it out so that the written measurment was the actual measurment to see if would fit your application, does anyone know where I can find this again??Sorry about the longwindedness ...but this is driving me crazy. I am just looking for a ballpark number.
Thanks for the Help
Chainmaker

 

[SimpleSimon]

Allow 11 inches vertical clearance above the mounting plate for your engine is a good rule of thumb. Since your seat back will be slanted at 45 degrees, the back edge of the seat needs to be at least 11 inches forward of the front engine mount - a 45 degree angle means that for each vertical inch the horizontal displacement is also one inch. I'd go forward a full foot, as your exhaust manifold comes forward off the cylinder.

Remember, the wheelbase length affects the Ackerman angle needed for steering stability - basically, the longer the wheelbase becomes while staying fixed in width, the lower the Ackerman angle needs to be. Easiest way to deal with that is to draw a T to scale that matches your wheelbase length and width, then measure the angle of a line between the base of the upright (your main frame line) and the crossbar of the T at the tip (the crossbar represents the wheelbase width. Ordinary graph paper is great for this.

edit: I just looked at the Warrior on AZ's site. I assume it is your intention to insert room for the engine behind the seat, and at the level of the seat bottom? If so, I'd lengthen the main boom at seat bottom heighth by 24 inchers, and then put in the angled riser to the rear dropout mount points, with a brace arcing above the engine space. The brace would be a good place to mount your fuel tank and your ignition module, perhaps a tool cache.

Given the Warriors design, that lengthening WILL affect handling significantly.

 

[srdavo]

Ballpark.....

Hi,
looks like 13 inches will give you plenty of room... that includes clearance for the stock exhaust pipe.

View attachment 24255

 

[srdavo]

My seat back will be at 45 degrees

I built my Tad seat at 45 degrees & for me, it was NOT comfortable. I changed it to a more upright angle. Not sure of the degrees.



Looks like I left plenty of room behind the seat, eh? hahaha

 

[chainmaker]

When You say "Given the Warriors design, that lengthening WILL affect handling significantly" are you just reffering to the ackerman steering ? This is correctable using the graph paper method you described correct? If you dont mind let me ask you about the other mods I am planning, I would appreciate any feedback, this is My first build so I kind of jumped in and I am finding issues that I didnt think about
1. I plan on widening the rear forks to fit a 27 x 10 x 15 racing slick
2. adding angled supports from the 90 degree bend in the forks to frame right at base of seat
3. The proposed horizontal boom extension to the rear of the seat would also go 6 inches in front of the seat tube to accomodate a bigger seat (for me and my little girl)
4. Switching tubing size from 16 ga to 14 ga 1.5 x 1.5
5. 20 in x 44 mm front bicycle rims with Pirelli 16 inch moped tires
6. Reducing the angle of the seat tube ( your seat looks more comfortable) which I will gain more space behind, and not have to lengthen boom as much
Besides Me being crazy, do You see any other problems brewing

 

[srdavo]

1. I plan on widening the rear forks to fit a 27 x 10 x 15 racing slick

is this a car tire?

 

[chainmaker]

Yeah... I spoked a 15x 10.5 wheel shell and found a hoosier drag slick to fit.

 

[srdavo]

Xtreme!!!!

WoW!!

Steering, at this point, doesn't seem all that important. (to me...... SimpleSimon will be able to help you with this) My questions involve whether the HT engine will make it roll & if it does.... how the heck are you going to stop it? That tire is a lot of mass....both to move & stop.

I'm NOT knocking your plans, by any means. Heck, I like it!!
I saw this beauty a few years back......
http://www.motoredbikes.com/attachment.php?attachmentid=2301&d=1192302211
http://www.motoredbikes.com/attachment.php?attachmentid=2302&d=1192302237

 

[chainmaker]

Well I ordered a couple of 20mm hubs for the front wheels that have disc mounts, and I also posted a question about rear discs and was advised against it. Speed isnt a huge deal right now, just a comfortable cruise is fine.. I am planning on a Pirate Cycle motor one of their performance ones when they come out this spring. You can check out what I have started ,not much right now (too cold outside) at my build website www.badbrainschoppers.com
Thanks
Chainmaker

 

[srdavo]

Well I ordered a couple of 20mm hubs for the front wheels that have disc mounts, and I also posted a question about rear discs and was advised against it. Speed isnt a huge deal right now, just a comfortable cruise is fine.. I am planning on a Pirate Cycle motor one of their performance ones when they come out this spring. You can check out what I have started ,not much right now (too cold outside) at my build website www.badbrainschoppers.com
Thanks
Chainmaker

Cool.... I really want to see this come together!!