KMX Trike Front Suspension

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gman1971
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Re: KMX Trike Front Suspension

Post by gman1971 » Aug 23, 2017 1:17 am

The Toecutter wrote:This means that at some point in the future, I will need to modify the suspension/knuckles in like manner. Thank you for sharing this information here.
Yes, once you get going fast enough and add some weight, but I advice you to do this before you need to.

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I am all about high-speed, low-drag, mid-drives and gears...
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Re: KMX Trike Front Suspension

Post by The Toecutter » Nov 10, 2017 11:51 pm

The roads where I am at are in rough shape and strewn with potholes. Last weekend, I was testing my coroplast tailbox/floor/sides(integrated as one piece) out, and somewhere around 25 mph, I heard a noise similar to dropping an allen wrench on concrete as my front right tire started making a noise similar to rollerblades on pavement.

The right-side spindle piece failed. Fortunately, I was only a few blocks from home. I checked the left spindle and it had cracks. This trike has been on some rough pavement on a regular basis, and I've kept the shocks at 80 psi, which may be a bit much since I'm around 150 lbs and do not yet have the electric drive or batteries installed and only had about 3 lbs of the body on it at the time(I expect the completed body with PVC pipe structure to be around 15 lbs when complete). I will lower it to 60 psi when I get the opportunity.

Today, the replacement steering spindles arrived. I think now would be as good a time as any to do this modification. Precisely how far was the new hole drilled from the existing one?

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Re: KMX Trike Front Suspension

Post by adam333 » Nov 12, 2017 4:19 pm

The Toecutter wrote:
The right-side spindle piece failed.
Did you took a picture by chance?

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Re: KMX Trike Front Suspension

Post by The Toecutter » Nov 14, 2017 12:44 am

I don't have any pictures. The camera on my phone stopped working and I cannot find the SD card for my digital camera.

It turns out that the new steering spindles aren't the same as the old ones that I am trying to replace. The mounting hole that you insert a screw through to hold the spindle to the aluminum block that holds the shock have different outer diameters for the new piece and the old piece.

The old spindles fit the suspension flush. The new spindle's mounting hole has too large of an outer diameter to fit into the suspension.

This means that I am going to have to either have the outer diameter of the new spindle's hole milled down to match that of the old spindle in order to mount the suspension, or have the aluminum of the suspension slightly drilled out to create a larger diameter mounting hole,

Any suggestions?

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Re: KMX Trike Front Suspension

Post by adam333 » Nov 14, 2017 10:12 pm

ya... they increased the diameter of this protrusion a year-ish ago. ( probably to make it stronger )

You have 3 possibility:

1- Ask your KMX vendor for the older component that have a diameter of 19.7mm ( they may no longer have that version though )
Image

2- Buy a cone drill bit 4-22 mm and re-drill the new spindle's mounting hole in order to reach the 22mm diameter on that side only:
Image
Image

I found the cone drill bit on Aliexpress for less than 4 us$ shipped.
If you go that way, make sure to hold the suspension in a big vise ( use a rags each side to avoid damaging the screw's head finish ) then drill at a low rpm. ( hold the drill with both hands )

3- Bring the old KMX spindle piece to your local welder and ask him to sand blast the paint and weld a line where the crack formed. ( buff the area in contact with the suspension adapter if needed )

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The Toecutter
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Re: KMX Trike Front Suspension

Post by The Toecutter » Nov 15, 2017 1:50 am

I like option 2, and I took a ruler to it and the outer diameter is already roughly 22 mm. I do not have a working set of digital calipers so I am guessing it is a few tenths of a millimeter too large then, given that it already looks like 22 mm with a ruler? I know a mechanic who can machine these down for me for a small fee, but before I do so, I need to know that this will work.

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Re: KMX Trike Front Suspension

Post by adam333 » Nov 15, 2017 3:52 pm

Drilling 22 mm will work. ( or even better, 7/8inches ) Worst case, you will have to finish it with a round hand file but it should take 30 sec.

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Re: KMX Trike Front Suspension

Post by The Toecutter » Nov 15, 2017 6:34 pm

Do you know precisely what the outside diameter is before modification? I measured it with a ruler and it was roughly 22 mm already, and am thinking that it is possibly a few tenths of a millimeter too large. I just want to confirm this before I have the pieces modified.

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Re: KMX Trike Front Suspension

Post by adam333 » Nov 15, 2017 8:37 pm

It is usually 22.03mm

I personally mill a hole of 23 mm in diameter.

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Re: KMX Trike Front Suspension

Post by The Toecutter » Nov 15, 2017 10:24 pm

Now I'm confused. I thought you were telling me to take the outer diameter of the cylindrical component that has an inner diameter mounting hole cut out, being that the mounting screw for the spindle and the suspension inserts through the inner diameter, and cut the outer diameter down so that it can fit into the suspension mounting block.

My initial understanding was that the outer diameter of the spindle's mount to the suspension is reduced from 22.03 mm(measured by your calipers) to 22.00 mm, and that is all.

Introducing a new number caused the confusion. Is 23 mm a typing error? Or is there a 23 mm hole I need to make somewhere?(which makes no sense unless I am drilling into the suspension mounting block to make its insert space for the spindle mount point a little wider, but I was earlier under the assumption not to cut into the suspension block at all and just reduce part of the spindle)

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Re: KMX Trike Front Suspension

Post by adam333 » Nov 18, 2017 5:22 am

Sorry about the confusion.

The outer diameter of the spindle's mount need to be reduced from 22.03 mm to 19.7 mm. ( not easily done )

The easiest way is to drill into the suspension mounting block from the rear to make its insert space for the spindle mount point a little wider ( 22 mm or 7/8 inches in diameter, done with the cone drill bit )

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Re: KMX Trike Front Suspension

Post by The Toecutter » Nov 18, 2017 9:18 am

Gman recommended drilling the mounting block last week, so that is what I will do. Thank you.

I may be riding it again today. Then I can pick up some PVC pipe and build a cage structure for my coroplast body shell. I've never ridden in a velomobile before and I'm quite anxious to try it.

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Re: KMX Trike Front Suspension

Post by The Toecutter » Nov 20, 2017 12:10 am

I got it working again and took it for a ride today. The keyed mounting hole on the aluminum suspension block had to have roughly 3mm diameter added to fit the new spindle. Hopefully your future designs will accommodate this. Hopefully this new spindle is strong enough that it doesn't break either.

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Re: KMX Trike Front Suspension

Post by adam333 » Nov 20, 2017 2:07 pm

Glad to hear that you solved this issue.

Right now, I am asking the outer diameter of the spindle's mount when some one order a kit. So I can ship the right dimension kit.

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Re: KMX Trike Front Suspension

Post by The Toecutter » Jan 24, 2018 9:24 pm

Here's a pic of mine now:

Image

The shocks look as good as ever.

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Re: KMX Trike Front Suspension

Post by adam333 » Jan 26, 2018 4:34 pm

Looking good :D

Thanks for the update.

Btw, did you installed the motor yet?

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Re: KMX Trike Front Suspension

Post by The Toecutter » Jan 26, 2018 7:04 pm

Not yet. I'm still trying to get the body complete. It works well though. It will probably be mid to late this year when I finally motorize it. I first want to get it as efficient as I can possibly get it on human power keeping in mind practical restraints. The motor's main purpose will be for acceleration and long-distance 30 mph cruising with pedal assist. Acceleration is in short supply purely under human power(1 kW for a few seconds at best). I am also tempted to make a rack and pinion steering system for it so I can build a new body with less frontal area.

I lowered the pressure of the shocks to 60 psi and this thing rides over potholes at 25+ mph smooth. I sanded down and painted over the surface rust on the screws with black paint. I have more than 2000 miles on the suspension by now(I don't have an exact figure because the speedometer is broken).

What parts require lubrication and/or other maintenance? This is holding up well after a year of use and I don't want to neglect it.

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Re: KMX Trike Front Suspension

Post by adam333 » Jan 29, 2018 10:12 am

The brass bushing are self lubricating, so this should not be an issue.

At some point, if the shocks start to make a "skweek" noise, you should lubricate the main cylinder.

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Re: KMX Trike Front Suspension

Post by adam333 » Feb 13, 2018 8:21 pm

Here is the adapter needed when using a 203mm rotor for the Avid BB5 or BB7 brakes:
http://www.tektro-usa.com/category.php ... uctid=1213
Image

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Re: KMX Trike Front Suspension

Post by The Toecutter » Feb 18, 2018 12:48 pm

Thank you for sharing this link. I plan to upgrade my brakes as the rotors I have are proving barely adequate for my usage of it under purely human power. Without your suspension kit, I wouldn't have found the KMX usable over 20 mph, either.

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Re: KMX Trike Front Suspension

Post by adam333 » Feb 19, 2018 9:26 pm

If you use the regen once the motor is installed, it will take care of most breaking as long you use a small wheel diameter.

( I tested it on the 700c Catrike though, and the regen/breaking is pathetic )

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