GP460 Engine On Friction Drive

Has anyone done this swap yet?

I'm doing it, will probably mount on my Raleigh men's cruiser w/7-speeds as a test bike.

I could use some helpful hints, especially about roller size, possible weak links and exhaust options.

TIA

Can't help much 5-7 cos i havn't got a GP460(yet) but i do have the BMP's kit.
My first impressions are that you'll need to fab a stronger(possibly even longer) U-bracket to take the power,even then the rest of the setup will no doubt need additional strengthing.
I did my U from 6mm steel instead of the standard 5mm,i know it's only 1mm diff but it's a handy improvement & i'm reluctant to go crazy adding weight.
Were u thinking of using the standard 1.25" one-way drive roller or swapping?


PS....sorry about the mud,it's been raining on & off here for the last 5 days.

5-7,

.02 worth

build a deeper, longer "u" channel so that you can can put 3 rollers in it.

one higher in the middle and 2 lower more toward the front and back. all of them touching to the same degree at once. tie the outer 2 to the center one by a chain loop on the far side ( opposite the engine)

i really think the sticking point is going to be getting enough contact without using so much down pressure that the resultant tire deflection just eats up the power anyway.

you're going to want to use a small enough roller to let the engine spin up to rpm easily to avoid long periods of high torque present at the roller/ tire. you are going to want to get to 22:1-23:1 for that engine and it's GOING TO BE FAST.

can't wait,
steve

fetor, I believe the front U-bracket will be the weak link. The thinner BMP front mount's strength has been questioned before and I don't particularly care for all front brackets' tendencies to pivot and twist. For additional strength I'm gonna triangulate this mounting position ala Staton gearbox, using additional struts.

Detonator Tuning, believe it or not I'm trying to keep this project as simple as possible. I will try controlling this engine's power with the standard engine channel and a single friction roller. To harness the power I'll use a small-diameter spindle. Then I'll keep speeds below the projected 40mph maximum until all systems are "GO!"

Other braces of 5/16" X 5" bolts are to be used front, midship and rear should add more than enough strength to the 1/8" steel engine channel.

I'll start off with a secondhand 1.25" Staton friction roller from "The Dragon Lady's" front drive. It only has a few hundred miles use with no wear on its contact surface. Surprisingly, the ends which ride inside the bearings wore its plating off. That slight wear allows the new bearings to SLIP-FIT!!! onto the spindle.

The BMP engine channel also allows a slip-fit for the outer diameter of the 1.375" bearing. It makes for a very freespinning roller. This is strange; the other vendor's press-fit bearing arrangement had always made the roller feel slightly tight and resistive after swapping in a new spindle.

There were other subtle reasons I decided to swap in another vendor's spindles. The BMP's driveshaft is only .50" diameter; its threaded end protrudes .125" into the clutch bellhousing area. I'm not saying the shaft might contact the crankshaft. For overkill, its diameter would worry me that it's not strong enough.

The Staton roller looks as tough as a grenade. Its diamond-hatch grip surface is very aggressive and the .625" ends are larger than BMP's driveshaft.

The GP460 I'll be using is Zomby Builder's old engine. It has limited miles and thanks Dave for a great price. It has Trevor Simpson's headkit/piston/cylinder w/15:1 compression. Dave ran the engine with racing gas due to high compression. I'm detuning to 13:1cr; then I can use 91/92 octane pump gas. Racing gas costs $120/5 gallons which is too rich for me. A $23 compression dome should make this beast streetable.

The only other high-performance parts will be the Dominator pipe from davesmotors.com like this one: http://www.davesmotors.com/s.nl/c.885035/n.1/it.A/id.1671/.f

Other builders on this forum have used this exhaust system affter modifying the pipe for clearance. Careful research predicts that the Dominator SHOULD clear all obstacles without modifications, just mounting bracket onto the engine channel. I will figure out the kit's front brace and goped tank location after this powerpipe is securely fastened.

fetor, I'm using Staton's rollers because they have more sizes to choose from. If a 1.25" spindle does not allow this modified 460 engine to rev high enough, then a 1.125" or 1.00" can be substituted. An online calculator has engine speed at 12,155rpm/13,500rpm/15,200rpm at a speed of 40mph.


That cross-references to gear ratio comparisons of 23.5:1 for a 1.25" roller, 26.1 for a 1.125" spindle and 29.4 if a 1.00" friction device is used.

Steve, I might try the 1.00" roller first. According to other people's testimonies this engine produces its maximum torque at 8,000rpm. That's sky high compared to Hondas, Subarus, Mitsubishis and others. Even though clutch engagement might be at 3000rpm, power might not be there unless gearing is very low.

Please share your experiences. At what gearing was your 460 engine most responsive in all your experiments?



to be continued...

5-7,

the 1.25" will be the ticket. 41.1mph @ 12500.

23.5:1 reduction thru a tranny like i'm using gives FANTASTIC accel. and you'll have MUCH less loss. my current "low" gear is 22.79:1 and i only go there for extreem headwind, 25mph and up. accel. is brisk to say the least. if wind is 5-10mph i can easily pull all hills etc. @ 19.29:1 running 40-45mph right around 11,000rpm.

you'll be above the HP peak of 11,000 but if 40's all you want then you're done. it will not be much over 50-60mpg but it will be a riot as long as it's hooked up.

best of luck, keep us posted

steve

after thought, what's the ratio on the 1.5" ? is there a 1-3/8" ?

as a point of interest, 21-21.5:1 is the best compromise ratio for me at the present time.

Steve, the 1.5" friction roller is equivalent to 19.6:1 when crossreferenced with two popular online calculators.

At 40mph, 10,100 rpm with this big spindle.

A 1.375" roller is equivalent to 21.35:1; at 40mph, 11000rpm.

I'm starting off with a 1.125" roller, which is like 26:1 gears.

13,500rpm at 40mph. With stiff gears, Dominator pipe, 13:1 compression and custom headkit, I believe this engine should still be producing hp at this speed.

in a perfect world the 1-3/8" roller is the ticket.

you'lll have all the power you're going to get at 11,000rpm, the CR and pipe are just going to make that # higher in pretty much the same spot.

you will still have "over revs" available though, mine see's 13,500 regularly just not at speeds i want to maintain. you are not going to like the sound of that motor sustained over 11,000rpm and that takes getting used to.

ps, 26:1 will feel "thin", what i mean is it will be hard to tell if it's completely hooked up because it will turn thru and rev real free.

steve

Detonator, I have roller sizes of 1.00", 1.125". 1.25", 1.375" and 1.5". I'll start off with 1.25" spindle instead of the 1.125" spindle and see what works after that.

Steve, can you explain your last statement "At 26:1 , will feel "thin", what I mean will be hard to tell if it's completely hooked up because it will turn thru and rev freely"?

5-7,

by "thin" i mean that there will be very little sensation of resistance, it will rev real easy and move on up in speed but there will be little "torque" pulling feel.

this sensation will be unsettling and you'll find yourself wanting to look to see if you are really hooked up.

it's odd enough that even with chain i was looking to see if i had derailed and running on a flange or something.

steve

DetonatorTuning said:

5-7,

by "thin" i mean that there will be very little sensation of resistance, it will rev real easy and move on up in speed but there will be little "torque" pulling feel.

this sensation will be unsettling and you'll find yourself wanting to look to see if you are really hooked up.

it's odd enough that even with chain i was looking to see if i had derailed and running on a flange or something.

steve

Click to expand...

Well, my Staton parts arrived. Dave sent me a 1.25" roller instead of the 1.125". I also ordered a 1.00" roller so I'll try that smaller one first.

Hmmm, this GP460 engine is weak on torque, huh?

I have a sneaking suspicion I'll be running TWO engines on my bike in the near future!!!

Yesterday I rode to work on "the Dragon Lady". The front engine died a mile from my building so I "limped" along on the rear engine until I got there. It was a fuel delivery problem I was able to correct after work.

I absolutely HATE to get stuck on the road and pedal home.. My way of justifying having twin engines on my projects.

No, I don't think it's too much power for a bike. Centrifugal clutches and sensible, disciplined throttle control will tame the beasts.

First things first. Single engine install.