Slow progress but progress (DIY two seater tadpole trike, 9hp Honda diesel)

[mikeyjd]

Originally Posted by Old Mechanic

Pictures as promised.

regards
Mech

Definitely my favorite thread going right now Pics are awesome. Keep it up!

[Frank Lee]

I'm not sure I get WHY anyone would want rear steer even if it was perfectly stable. When maneuvering in close quarters it seems to me smashing the rear bodywork into things would be much more likely. What's the point?

[user removed]

The engine is a Honda GD410 manual start diesel. I tried copying the manual and pasting it here but it is secured or for some reason I am not get it to paste on this site. I guess it could spell trouble if I did, so you can probably find it on the net with this info.

I've never heard it run, not so sure I have enough left in my old bones to pull start an almost half liter 20 to 1 compression diesel engine. When we get the primary hooked up then I can start it with the Harley starter. The fuel tank that came with the engine holds less than 5 liters of fuel, probably 2-3 hours run time.

regards
Mech

[HHOTDI]

Excellent work O.M., sure is coming along nicely. So excited to see your progress on it, def one of the highlights to my evening to come to see what you have done/posted as updates! :{)

[freebeard]

Thanks for taking the time, but

slight upward angle instead of a steep downward angle

is ambiguous. Any drawings or pictures. Or just, how would the idler arm theory translate to a tricycle?

Old Mechanic -- Dig the pix. I do hope you use an equivalent grade for the four bolts that hold the axle beam, the holes in the square tube are sleeved and you plug the ends of that crossbar so it doesn't distort.

[owly]

Originally Posted by freebeard

Thanks for taking the time, but

is ambiguous. Any drawings or pictures. Or just, how would the idler arm theory translate to a tricycle?

Old Mechanic -- Dig the pix. I do hope you use an equivalent grade for the four bolts that hold the axle beam, the holes in the square tube are sleeved and you plug the ends of that crossbar so it doesn't distort.

I haven't examined how this would "translate" to a three wheeler. Body lean relative to the suspension is in the front on a three wheeler with two in front, and is the compression of one front spring and extension of the other. A very different thing than on a truck where you have two solid axles, and a frame, and the steering axle changes it's relation to the frame. On the three wheeler with rear steer, the rear wheel stays true with the body, and the front wheels do not. Thus you inherently do not have the problem of lean causing steering. The way I would approach the problem is as I have said. Use positive caster, and "rake" to put the contact patch of the steering tire forward of the kingpin axis so that centrifugal force, which is pulling toward the outside of the turn is acting to create a steering force toward center on the tire. Thus if you were to let go of the wheel in a turn, it would tend to steer toward center of it's own accord. Alternatively you could use a mass on a swing arm that you would be moving when you steered, and as the centrifugal force of your turn increased, that mass would want to swing toward the outside of the turn. Properly attached to the steering linkage, this would provide an increasingly strong force against you wanting to move the wheel back to center. This would be extremely simple............. A ten pound pendulum for example mounted on a longitudinal axis pivot with a small damper shock, and a linkage with a bell crank to change direction so it could be connected directly to the forward and backward moving drag link that connects to the rear wheel. I'm not good at drawing word pictures... but I can close my eyes and see exactly how that would work...........

I've been talking about this for years........... and haven't built one. I did learn some very interesting things about caster and rake building a flying machine with a tricycle stance. I actually have pieces left over including the kingpin and front wheel assembly, and a piece of frame that could be used that already has a 10 deg angled hole for the kingpin, so it could be used as original easily, or inverted to give 10 deg positive caster angle or 10 deg negative caster. The steering assembly with the wheel can easily be reversed to place the wheel forward or rearward of the kingpin steering axis. It would be interesting to build a one rear wheel steer setup out of this as everything is there to try 4 different configurations. I also have a seat that will attach. It's all based on a 2" aluminum square tube. With a front wheel drive assembly of some sort, it would make a good test bed.

Howard
Howard

[user removed]

Concerning the rear steering. While I have considered rear steering, I chose to not try to incorporate it in this vehicle, since I already have the front suspension as a complete design with one of the most proven histories of any suspension ever made on the planet.
While it may not be the "best" option, it certainly passes the test of time and parts are readily available.
Without rancor or any attempt to project anger or even frustration, I revert to my long dead aunt"s sign that was posted over her swimming pool.

"I don't swim in your toilet, so please don't pee in my pool."

Can we please take the rear steering tangent to it's own thread.

Thank you very much and your cooperation would be appreciated.

regards
Mech

[user removed]

Originally Posted by freebeard

Thanks for taking the time, but

is ambiguous. Any drawings or pictures. Or just, how would the idler arm theory translate to a tricycle?

Old Mechanic -- Dig the pix. I do hope you use an equivalent grade for the four bolts that hold the axle beam, the holes in the square tube are sleeved and you plug the ends of that crossbar so it doesn't distort.

The mounts for the front suspension assembly are (I believe) grade 8 bolts, and the mounting points are on the vertical tubes, that are welded to the top tube. The actual mounts themselves are a piece of thick walled tubing that is welded to the vertical tube where the mounting bolts pass through the welded tubing and do not bear on the square tubing. Like yourself, if it had been bolted through a hole drilled in the tubing, it would certainly have been a weak point in the design. As it is you could probably lift a Chevy Surburban with each individual mounting point, Long before any deformation occured in the frame structure the axle itself would bend under any suspension impact that could be imagined.

That is one reason why I am as pleased as possible with the workmanship that my friends shop has performed. When they have finished to the point where I take the vehicle out of their shop, I will probably get either my brother or myself to TIG weld gusset plates for further reinforcement of critical structural areas to provide even more strength, particularly in the engine mounting, suspension, and passenger compartment areas.

The other side of the coin is it is also essentail to leave the front and rear sections of the frame with areas that can collapse in the event of any collision. If this was not done and the ends of the structure were actually too strong, then collision forces would not be absorbed and would be transferred directly to the occupants. Primarily those areas are the frame in front of the front suspension, and behind the mounting points for the rear suspension, engine and transmission.

regards
Mech

[Kenny]

Originally Posted by owly

I don't have any references.......... I built quite a few of the reverse truck loaders back in the 80's. At first they were a handful to drive....... worse if you didn't reverse the axle.

Howard, I hate to be a party pooper, but...

RWS had been around 100+ years, and there's precious few that were safe road vehicles - the vast majority are low speed material handling forklift types.

The problem cannot be corrected with steering mods. When you design with the CoM forward of the steer wheel(s), but behind the front axle, you cause the CoM to move laterally outside the centerline turn radius during turns. When that happens, the angular velocity of the rear wheels increases, causing significant side loading on the rear tire's contact patch(es). Steering becomes unpredictable because of the high lateral loading of the rear (steer) tire's contact patch(es) during turns. Adding positive OR negative caster to the steer wheel(s) may improve steering 'feel', but does nothing to eliminate the core problem, in fact, altering the steering geometry creates a dangerous false sense of security at higher speeds when the rear steer tire grip is eventually lost due to increased lateral contact patch loading during turns.

[Kenny]

Originally Posted by Old Mechanic

Can we please take the rear steering tangent to it's own thread.

Thank you very much and your cooperation would be appreciated.

regards
Mech

WOOPS! I responded to the RWS issue before reading. My error and I sincerely apologize OM. I'll be more careful not litter this informative thread.

-kenny-