Speed De-limiter device

[smokey_jo]

Following inspiration from the levo thread where someone had 3d printed a planet gear system to fool the speed limit I decided to see if I could do something similar for my deore sommet.

Following a bit of experimentation the latest prototype has just passed testing on the road.

Here's a little video of it in motion in the work stand.

https://photos.app.goo.gl/9w5ozTuhfjKGbV636

It's laser cut out of acrylic and the casing is glued together.

The final version will be cut out of delrin once I've found a suitable glue or thought of a better way to join the casing pieces together.

Also need to decide on a better mounting point and system for the speed sensor rather than a zip tie but that shouldn't be difficult. Until I'm happy that the gear is reliable I like having the ability to put the sensor back into original position in case of failure.

Speed increase before limiter cuts in according to GPS on my phone seems to be around 35-40% and obviously speed and distance readings on the steps head unit won't be correct.

A sheet of 2 or 3mm thick delrin should be around £10, magnet around £1 then you just need to find someone with a laser cutter to give you around 20 mins machine time.

Should work fine with any 6 bolt disc hub so long as you have 10 clearance between disc and frame and you can mount the speed sensor somewhere suitable. Only variable in the dimensions will be the diameter of the axle but this is easy to change in the drawings.

I'll commute in to work on it next week to see how it stands up to road use and if it survives I'll try it if road in the slop. If the acrylic works ok then delrin should be fine as it's not as brittle as acrylic.

 

[R120]

I was wondering where you had got to with this - great progress, still thinking getting the sensor designed for disc brake magnets might be a good idea? Top bodging!

 

[smokey_jo]

Possibly but trying to keep costs down.

Also noticed that the magnets produce a bit of drag as it passes over the rotor bolts. Might fill the recesses with a bit of silicone and put some epoxy on the back of the magnet. Could try a smaller magnet too to reduce the effect.

 

[R120]

Could you make a new housing for the existing sensor? That would be pretty neat if you could, one that locates it at the back?

 

[smokey_jo]

My initial thinking is to modify the circular part by cutting off one half of the round part so it sits flat against the dropout and use a no-nails sticky pad to stick it on.

This allows it to be put back in the correct place easily should the need arise whilst out on the trail.

I'm all about the low tech solutions ?

 

[smokey_jo]

So the shonky low tech acrylic version has lasted a baptism at Stainburn forest where it survived plenty of roots, rocks, dust and drops.

Got the occasional error when riding really slowly as in slower than walking pace but otherwise no issues.

Just needs some wet weather testing now.

 

[smokey_jo]

Just tried it on the wife's e-sommet (the xt version) and as the DT wheels have a different axle diameter it needs a sun gear with a slightly bigger hole to allow the planet gear to rotate without catching.

Also occurred to me that in the case of a catastrophic failure there's no need to move the speed sensor back to the original location you can just pop a magnet onto one of the disc rotor bolts

This means that I can look at a permanent mounting solution at the dropout without having to keep the original fixing hole intact.

I think that because of this it can work on any bike with a 6 bolt rear disc rotor, somewhere suitable to mount the speed sensor and clearance of 12 mm between the disc rotor and the inside of the dropout. Only variable is going to be diameter of wheel axle.

 

[Gary]

What do you mean by "diameter of wheel axle"?
all E-sommets use a 148x12mm axle
ie. 12mm diameter axle. 148mm hub end cap to end cap.

seeing as the axle and end caps don't turn I guess you mean your device has to be greater internal diameter than the end caps to allow it to spin freely. (and must be somehow mounted to the hub shell?).
BTW end cap diameter/shapr will be down to individual hub manufacturers rather than specific to bikes. (pretty much all emtbs seem to be rear 148x12 boost spacing)

Pretty cool idea. I'm not sure I'd expect small plastic cogs to last a Scottish winter of rough manky DH riding though if left unsealed. I don't suppose that would be too easy to do given the limited space but have you thought about some sort of sealing for it?

 

[smokey_jo]

The 12mm bit is the diameter of the axle - the sleeve for the axle varies from manufacturer to manufacturer.

The DT swiss axle on the XT version is a constant diameter. Inboard of the end cap on the Deore version the axle sleeve diameter reduces by a mm or so.

If the sun gear is a good interference fit onto the axle sleeve then you don't need anything to fix it to the hub shell. The disc rotor bolts provide the drive for the rest of the device to rotate around the sun gear which remains stationary.

I'm making a mod to the prototype tonight (got to make a new one for the DT wheels anyhow) which will allow it to be removed and replaced without tools which will make cleaning a 2 minute job.

Using a laser cutter keeps the costs much lower and speeds up production time vs 3d printing but means sealing would be more difficult.

As I have laser cutters at my disposal it makes sense for me to use them.

If you fancy testing one in some Scottish muck I'll send you one up - it's so dusty down here in Yorkshire at the minute!

 

[Gary]

I'd absolutely love to test one for you.
Thanks.
it's actually bone dry, loose and and dusty up here just now too. though I'm certainly not complaining.

This is usually a very wet technical trail (steeper than it looks) yesterday
it's never usually dry enough not to end that trail minging but as you can see I managed to take a high line round the only two puddles left. (possibly the only two left on the entire hill so thought it'd be rude to disturb them )

The DT swiss axle on the XT version is a constant diameter. Inboard of the end cap on the Deore version the axle sleeve diameter reduces by a mm or so.

The 2019 E-sommets no longer use DT hubs. They use Novatec,
the disc side end cap is stepped (wider diameter at the dropout) and flanged at the bearings end. looks to have enough room for your device on the narower diameter section but obviously this means the inner portion of your device could not be mounted to the end cap without some sort of split shim. (if you get what I mean)
I can measure end cap diameter, spacing etc for you.

PM me when you're further forwards with it all.

 

[smokey_jo]

That looks like a doozy of a trail !

Sounds like you're on the same wheels as on my 2018 Deore version then. The sun gear has a cut in it which allows the perspex to flex enough to clear the outer section but then grip onto the narrower inner section.

You need the split on the sun gear to be just about closed otherwise it will catch the planet gear as it passes it.

I'm actually pleasantly surprised as to how well the acrylic version withstood the ride - it's not really exposed to anything unless you are unlucky with a branch kicking up off the floor. Hardly any dust got inside the casing either - mud is probably going to be another matter though!

Assuming the next version test goes well I'll send you an acrylic one to abuse whilst it's dry out, send me a measurement of the diameter of the narrower section of the end cap on your wheel.

 

[Gary]

That looks like a doozy of a trail !

Yeah. it's a lesser known short DH trail. it doesn't link to the rest of the DH tracks so gets less uplift traffic from DH bikes and is a level above a lot of the mid level stuff a lot of trail bike riders tend to ride (if wet anyway)

Sounds like you're on the same wheels as on my 2018 Deore version then.

The hub is this one
D462SB-B12
rims are WTB ST lite i29

The sun gear has a cut in it which allows the perspex to flex enough to clear the outer section but then grip onto the narrower inner section.

You need the split on the sun gear to be just about closed otherwise it will catch the planet gear as it passes it.

Ah.. I get you. Cheers for explaining.

I'm actually pleasantly surprised as to how well the acrylic version withstood the ride - it's not really exposed to anything unless you are unlucky with a branch kicking up off the floor. Hardly any dust got inside the casing either - mud is probably going to be another matter though!

Assuming the next version test goes well I'll send you an acrylic one to abuse whilst it's dry out, send me a measurement of the diameter of the narrower section of the end cap on your wheel.

that'd be cool.
I'm running a peartune (switchable version) just now.
will PM you measurements next time I have the rear wheel off.

 

[Gspot]

Gary did this ever work on your Vitus? I believe the sensor is a little further from the hub than Levo?