CityCyclingEdinburgh Forum » Debate!

Speed limits on equipment

(11 posts)
  • Started 13 years ago by Smudge
  • Latest reply from crowriver

No tags yet.


  1. Smudge
    Member

    Prompted by a recent thread which mentioned some trailers having a maximum speed limit of 25 kph/mph, I have to confess I was surprised and wondered if anyone else had seen equipment with seemingly low/arbitary speed limits applied to them?

    After all, my experience is obviously limited to a reliable sample of one, but I would have thought 25mph (let alone kph) easily attainable(exceedable!) by the average cyclist on a downhill, indeed in my own limited experience 40mph is common on steeper hills and 50mph not unknown, and I know there are riders out there who are an awful lot faster than me!

    Or is it just a get out if it fails or the rider loses control? Don't sue us we told you so?

    Posted 13 years ago #

  2. wingpig
    Member

    With trailers (in addition to concerns about braking performance) I expect it would be to prevent bouncing and subsequent mis-alignment upon landing (even when travelling in a straight line) and subsequent fishtailing, with the potential for the trailer to swing to one side hard enough to yank the towing bike over (if the hitch didn't give way (our foul the wheel) first). On bends, even a dampened hitch or suspension might not prevent some sideways skittering, with similar potential results, particularly if the trailer decided to skitter as far as a kerb and start bouncing about.

    Posted 13 years ago #

  3. Smudge
    Member

    Hmmm, interesting. Still feels like an artificially low limit unless the trailer design is flawed, after all, trailers get succesfully towed behind powered bikes at vastly higher speeds without bouncing/skittering issues. (Not saying you're wrong, just thinking "aloud")

    Posted 13 years ago #

  4. wingpig
    Member

    Likewise - never used a trailer myself though I have one we got for free in the shed which I've still to try out. Where/how do trailers attach to inhumanly-powered bikes? Is there any crossover in the form of trailers which could be used on both? Presumably anything designed with the intent of being dragged around by pedalling will have had weight-reduction priorised above performance-at-high-speed.

    Posted 13 years ago #

  5. crowriver
    Member

    I did a downhill with the fully loaded Winther Donkey last summer from Beecraigs, also No.1 son on back seat.

    Mostly it was fine, and managed to get up to 17mph in a controlled descent. If I went much over that, it started bouncing from side to side, and oscillating so I could feel sidewards movements. I then had to slow down or sometimes stop so that the bouncing ceased. Similar effects were observed if the trailer hit a big pothole or ripple in the road (eg. the ruts carved by buses at stops). Quite disconcerting, but the bike never fell over.

    The Carry Freedom Y-frame, with its lower centre of gravity and lower hitch point, does not have this issue but I have tipped the trailer over twice: both times it was piled higher with stuff than was perhaps sensible, and I was taking corners.

    It's common sense really that you shouldn't try to go too fast with a heavily laden trailer: apart from anything else your stopping distance increases noticeably, even in warm and dry conditions.

    I understand that single-wheeled trailers like the Bob Yak or the Extrawheel are capable of higher speeds and even off-road riding due to their ability to track the lead bike. Tagalong trailer bikes for human cargo work on a similar principle.

    The main downside of single wheeled trailers is they are less not rotationally decoupled from the lead bike so if they start to topple over, so does the lead bike! Others are that they are not as stable, and cannot carry as much weight as two wheeled trailers.

    Posted 13 years ago #

  6. Smudge
    Member

    @Winpig, not the easiest to describe, but usually the towhitch frame is attached to the bikes subframe under/to the sides of the pillion seat and extends behind the bike then down to the actual hitch centrally low down behind the back wheel. I wouls doubt most would be suitable for pedal use as their weight is less critical and the tyre drag will be higher with 70+mph rated tyres. The basic designs could certainly be adapted/used. I've seen a quite nice one for instance that used an old car roofbox as a lightweight lockable container on top of the trailer chassis.

    @Crowriver, I'm speaking from a position of relative ignorace when it comes to bicycle trailers, but assuming they don't use suspension, would altering tyre pressures help reduce the bouncing? Bouncing alone shouldn't cause a trailer to yaw, (witness unladen motor vehicle trailers which seem to spend half their time airborne!) there has to be another factor and if it is a persistent problem then to my mind it points towards a problem with the weight distribution/towhitch position/suspension design or similar? Certainly with a coxswean and yourself added to the weight of your bike the trailer, unless very heavily loaded, shouldn't be too heavy compared with the tow vehicle. Again, curiosity not criticism ;-)

    Posted 13 years ago #

  7. wingpig
    Member

    "...centrally low down behind the back wheel..."

    Don't some pushbike trailers use modified rear hub attachmenty-thingbies? I assume they'd be immune from chainstay-mounted swervey-effects...

    Posted 13 years ago #

  8. crowriver
    Member

    This is the Winther Donkey in action:

    Here is a detail showing the hitch, which clamps to the rear stays using wing nuts. Very simple but a wee bit of a faff to get on and off.

    They modified the original design by putting the 'roll bar' on the hitch to stop the trailer from turning over. This means you can definitely feel the bouncing when it happens, though to be honest it never felt like it was going to tip the trailer over, nor the bike even when I could hear a thump thump thump as the tyres alternately landed back on the tarmac at 18mph...

    I am probably guilty of running the tyres at too high a pressure in the early days, though I still adhere to the principle that the heavier the load, the firmer they need to be. Essentially its a centre of gravity issue with shopping trolley/golf cart style trailers.

    I like the Winther Donkey a lot for its nifty features: mudguards, sturdy plastic box built in, flexible steel rack/shelf, waterproof stretch cover, built in bungee cord, and a single shopping trolley castor on the underside for wheeling it around the supermarket. If the hitch was not so heavy (1.4kg) I'd probably leave it on one of my bikes permanently, as it's fiddly to get on and off. It also could get in the way of the tagalong boom arm, so can't leave it on the hybrid. This means I don't use that trailer much now, though it has given good service on two cycle camping trips.

    For touring the Cary Freedom Y-Frame is the business. The hitch is really neat and light so I have two, one on the folder and one on the hybrid, meaning I can easily tow the trailer (and my DIY Y-Frame large) from either bike.

    Posted 13 years ago #

  9. crowriver
    Member

    Here's the Winther Donkey post Beecraigs at Linlithgow Loch, summer 2010.


    Surveying the Loch, Linlithgow, Summer 2010

    Oh yes, I forgot one key advantage of the Winther Donkey. Because the hitch is centrally mounted, when you park the bike (using a bipod kick stand) it does not tip it over, even loaded with heaps of camping gear. If there's a heavy-ish load on the Carry Freedom Y-Frame, due to the one sided hitch it will tip the parked bike over. Hence I have to lean the bike against a wall or tree when I want to leave it unattended for a moment.

    Posted 13 years ago #

  10. Cyclingmollie
    Member

    @crowriver The Winther Donkey looks ideal for shopping and picnics. Does it fold down for storage?

    The views of the passengers also have a bearing on this issue. I used to make the girls laugh by swerving around when they were in the trailer. But they didn't like bumps or potholes. IIRC they also shouted at me to slow down at times. I didn't go down any really steep hills as there weren't any on the routes we chose. But I never felt that the trailer was compromising the bike's handling or stability (though braking was affected).

    Posted 13 years ago #

  11. crowriver
    Member

    The Winther Donkey looks ideal for shopping and picnics. Does it fold down for storage?

    No it doesn't, but it stands upright when not in use so doesn't take up much space. See this one in Berlin somewhere:

    That little shelf can be flipped to vertical to keep your load in instead.

    I got my trailer quite cheaply as an ex-demo deal. The full RRP is over 200 quid if I recall correctly. It's quality though, powdercoated steel frame, good wheels and tyres, etc.

    Picnics, shopping are great with the trailer. Going to the beach too.

    Found pictures of a cargo bike and trailer-tastic house move in Vienna, including a seriously overloaded Winther Donkey. Even more impressive than an earlier experiment I saw from Portland on Youtube a while back:

    http://mirkojavurek.wordpress.com/2011/07/12/fahrrad-ubersiedlung/

    Posted 13 years ago #

RSS feed for this topic

Reply

You must log in to post.


Video embedded using Easy Video Embed plugin