Introduction: Ski Sledge for Baby
This is an entry in the
Epilog Challenge 9
My favourite sport is cross country ski, and I liked very much to go ski with my wife. But since we had a son we couldn’t go together: one of us had to take care of the baby while the other was skiing.
Then, during a winter holiday in Seefeld (Austria) I saw a sledge for rent. I tried it, e… Voilà, we were skiing together again, but not only me and my wife, also our little son was with us in the sledge.
So I started to build our (my and of my son) own sledge; there are sledges already done and very well built on sale, but they are REALLY expensive. Since I was aware that I wouldn’t use it very often, mine had to be simpler and much, much cheaper…
Step 1: Overview
I built the sledge around a sled I found in a big sport shop for around 30€. The best thing of this sled is that it is equipped with safety belts, so the baby cannot fall off the sled while we are going.
I made 2 rods to pull the sledge. I wanted them to be stiff so that the sledge would not get on me when I brake or slow down. I used 2 plastic cable ducts, as they are light but stiff enough, with a rope inside. I attached about 0.5 m (1ft 8in) of elastic rope to dampen the tugs made when skiing. At both ends of the rods a washer a little wider than the cable duct keeps the rope in place, and carabiners are fixed in a loop of the rope. On the sides in front of the sledge 2 U bolts are fixed, on which the rod’s carabiners are hooked. The rods fixing is strenghtened by 2 metal sheet hooks.
In the first test the sledge had a worrysome amount of lateral sliding, so much that it could tip if it hit a hole or a block of snow, so I modified it and added a second hook for the rods and 2 little drifts in the back of the sliding shoes. At the sledge’s end the rods have a hole on the side in which a bolt head is inserted to keep the rod fixed to the sledge.
The rods, once fixed to the sledge, are then hooked to two rings worn to a bottle belt that I’m wearing when I go to ski.
The sledge works pretty well, it’s also considerably lighter than “professional” ones, and the baby seems to like it very much, since he does good sleeps on it, and enjoys fast descents when awake.
Step 2: Materials
Before I start to describe how I built this sledge I'll make a short premise: Since I'm not a native english speaker I find difficult to explain in detail the sequence of operations, so the building steps are illustrated by photos with numeric references to the materials I used. Being the assembly very simple I believe they are quite easy to understand. Few words describe some additional details.
The dimensions are in metric system; I put in brackets the corresponding approximative imperial linear dimensions, but for bolts and nuts I used only metric notation.
- Bebè sled “BOBEE”
- (1) 2 x ~10 cm x 3 cm (4 in x 1.2 in) metal sheets
- (2) 2 x ~10 cm x 3 cm (4 in x 1.2 in) metal sheets
- (3) 2 x M3 U-bolts
- (4) 2 x M3 hexagonal hollow head bolts
- (5) 10 x M3 hex nuts (dadi)
- (6) 4 x hexagonal head M4 bolts
- (7) 4 x ~3 cm x 3 cm (1.2 in x 1.2 in) metal sheets
- (8) 4 x metal sheet hooks
- (9) 6 x washers
- (10) 4 x M4 wing nuts
- (11) 4 x M2.5 bolts
- (12) 1 x ~8 cm x 3 cm (3.15 in x 1.2 in) metal sheet
- (13) 1 x ~6 cm x 3 cm (2.4 in x 1.2 in) metal sheet
- (14) 4 x M2.5 nuts
- 2 cable ducts, about 2 cm (0.8 in) of diameter and 1.7 m (5 ft 7 in) of lenght
- 2 ropes, 1.25 m (4 ft 1 in) long
- 2 elastic rope, 0.5 m (1 ft 8 in) long
- 4 carabiners (moschettoni)
- 2 washers
- 2 metal rings, for bottle belt
- Fishing wire
Step 3: Drill the Holes in the Sledge
I first drilled the holes for the bolts in the metal sheets, then taking the sheets in place on the sledge with duct tape, I made the holes in the sledge. The position of the U bolts and hooks on the sledge was not critical, so I didn’t made drawings or taken submillimiter measures, the only thing I paid attention to was that they were about simmetrical on both sides. The diameter of the holes are of the same nominal dimension of the bolts, so for example, for M4 bolts the holes are 4 mm (~ 0.16 in).
Step 4: U-bolts and Hollow Head Bolts Assembly
With the holes done I started to fix the U bolts and the hexagonal hollow head bolts. I used little metal sheets on both sides of the holes to strenghten the fixing, because I suppose that the plastic of the sledge alone would break under the stress of the pulling rods.
Step 5: Metal Sheet Hooks Assembly
Then I fixed the metal sheet hooks, with strenghtening metal sheets in the inside of the sledge (on the outside the washer and sheet hook keeps the plastic safe). Since the hookes have to be fixed and unfixed every time the sledge is used I used wing nuts to tighten them quickly.
(Optional: Since the wing nuts are loose when the rods are not fixed, to prevent them to unscrew completely and get lost I crimped the extremity of the bolt, just squeezing the last 2-3 threads with pliers)
Step 6: Drifts Assembly
At last I fixed the drifts at the back of the sledge; the drifts are on the inside, with a little strenghtening metal sheet on the outside. They extend only about 0.5 cm (0.2 in) beyond the surface of the skates, but they have proven themselves effective in stabilizing the direction, and have a negligible friction in the snow.
Step 7: Pulling Rods Assembly
To build the rods I used 2 cable ducts, about 1.7 m (5 ft 7 in) long, with a rope inside and 2 carabiners at both ends. The rope inside is about 1.2 m (3 ft 1 in), plus about 5 cm (2 in) for the knot in the carabiner. About 0.5 m (1 ft 8 in) of elastic rope is sewn at the end of the rope inside the rod. The other end of the elastic rope is looped around the other carabiner and sewn. Two washers prevent the carabiners to slip inside the rod. The elastic rope is lightly tensioned, so the carabiners are kept sticked to the rod’s ends. I fixed the assembled rods to the sledge and made a sign on the side of the rods corresponding to the hollow head bolts, then I removed the rods from the sledge and drilled a hole of the same diameter of the hollow head bolt, paying attention to not damage the rope inside the rod. This is to prevent the rods from slipping off their position.
For all the seams I used fihing wire, for its tensile strenght.
Step 8: Bottle Belt
Last detail is the bottle belt, to which I sew, always with fishing wire, 2 metal rings on the sides to hook the carabiners of the pulling rods.
Step 9: Ready...
OK, now that we have all the pieces together let's see how to mount them.
It is quite simple, just hook the rod's carabiner to the U-bolt, fit the hollow head bolt in the hole on the side of the rod, put the metal sheet hooks on the rod and tighten the wing nuts, that's all.
Put the baby on the sledge, fasten the seat belts.
Hook the other rod's carabiners to the rings in the bottle belt and go to ski.
Step 10: ... Go
Just a couple of videos to show the sledge in operation...
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